Techniques for Interface Stress Measurements within Prosthetic Sockets of Transtibial Amputees: A Review of the Past 50 Years of Research
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paper_title: Considerations for development of sensing and monitoring tools to facilitate treatment and care of persons with lower-limb loss: A review

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Sensing and monitoring technologies offer enormous potential to enhance the quality of healthcare provided to persons with lower-limb loss. Incorporation of these technologies into the rehabilitation process creates opportunities for a multidimensional exchange of timely, relevant, and meaningful health information between patients, their prostheses, and healthcare providers. Here, the authors envision a conceptual model for enhancing prosthetic rehabilitation through use of integrated physical and/or biological sensors and remote monitoring methods. Several specific applications that target treatment, diagnosis, and prognosis of health issues faced by persons with limb loss are proposed in an effort to demonstrate how collecting and using objective data can facilitate clinical decision making. Contemporary integrated sensors that may be used in these applications are reviewed and their limitations discussed. It is hoped that the considerations proposed here may serve to stimulate development of clinically useful monitoring and sensing technologies and promote their integration into routine amputation rehabilitation.
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paper_title: Clinical investigation of the pressure and shear stress on the trans-tibial stump with a prosthesis.

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A system for measuring pressures and bi-axial shear stresses at the body support interfaces has been developed. This system has been used, in five unilateral trans-tibial amputees, to investigate the stresses at multiple points on the residual limb and prosthetic socket interface during standing and walking. The subjects investigated regularly used a patellar-tendon-bearing socket. The maximum peak pressure at the measured points was 320 kPa over the popliteal area during walking. The maximum shear stress was 61 kPa over the medial tibia area. Variable wave-forms of stress during walking were observed at the different measured points. The influence of the angular alignment on the stresses was investigated on one subject. It was found that a miss-alignment of +/- 8 degrees produced a change in peak longitudinal shear stress of between 8% and 11.5%.
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paper_title: Review of the Socket Design and Interface Pressure Measurement for Transtibial Prosthesis

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Socket is an important part of every prosthetic limb as an interface between the residual limb and prosthetic components. Biomechanics of socket-residual limb interface, especially the pressure and force distribution, have effect on patient satisfaction and function. This paper aimed to review and evaluate studies conducted in the last decades on the design of socket, in-socket interface pressure measurement, and socket biomechanics. Literature was searched to find related keywords with transtibial amputation, socket-residual limb interface, socket measurement, socket design, modeling, computational modeling, and suspension system. In accordance with the selection criteria, 19 articles were selected for further analysis. It was revealed that pressure and stress have been studied in the last decaeds, but quantitative evaluations remain inapplicable in clinical settings. This study also illustrates prevailing systems, which may facilitate improvements in socket design for improved quality of life for individuals ambulating with transtibial prosthesis. It is hoped that the review will better facilitate the understanding and determine the clinical relevance of quantitative evaluations.
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paper_title: A review of prosthetic interface stress investigations.

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Over the last decade, numerous experimental and numerical analyses have been conducted to investigate the stress distribution between the residual limb and prosthetic socket of persons with lower limb amputation. The objectives of these analyses have been to improve our understanding of the residual limb/prosthetic socket system, to evaluate the influence of prosthetic design parameters and alignment variations on the interface stress distribution, and to evaluate prosthetic fit. The purpose of this paper is to summarize these experimental investigations and identify associated limitations. In addition, this paper presents an overview of various computer models used to investigate the residual limb interface, and discusses the differences and potential ramifications of the various modeling formulations. Finally, the potential and future applications of these experimental and numerical analyses in prosthetic design are presented.
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paper_title: Scientific validation of two commercial pressure sensor systems for prosthetic socket fit

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The concept of measuring pressure at the interface between the stump and the prosthetic socket could provide valuable information in the process of prosthetic socket fabrication, modification, and fit. Two systems, the Rincoe Socket Fitting System (SFS) and Tekscan's F-Socket Pressure Measurement System, have been commercially designed for in situ interface pressure measurement over the past decade. Their use is not common in prosthetic practice, perhaps due to questions of cost effectiveness and the difficulties of interpreting the data. Another concern is the use of sensors for pressure measurements in areas of high contour and complex geometries such as the stump. Before these systems can be used in a clinical setting, it is necessary to determine the reliability and accuracy of each system. In order to assess the clinical validity of the Rincoe SFS and F-Socket systems, a series of trials was conducted to evaluate different aspects of sensor performance, namely; accuracy, hysteresis, drift and the effect of curvature. The sensors were subjected to tests in flatbed and custom-designed pressure vessels. Overall results indicated an accuracy error for the Rincoe SFS system of 25% (flatbed) and 33% (mould), with a corresponding 15% (flatbed) and 23% (mould) error in hysteresis, and 7% (flatbed) and 11% (mould) drift errors. The F-Socket system demonstrated an 8% (flatbed) and 11% (mould) accuracy errors, 42% (flatbed) and 24% (mould) hysteresis errors, and 12% (flatbed) and 33% (mould) drift errors. These findings indicate favourable results for the F-Socket Pressure Measurement System compared to the Rincoe Socket Fitting System with respect to its accuracy errors only. Nevertheless, it is the authors' belief that these systems are adequate in indicating areas of high pressure at the stump socket interface for clinical purposes, but both systems should be used with caution.
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paper_title: Development and validation of a 3D-printed interfacial stress sensor for prosthetic applications.

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a b s t r a c t A novel capacitance-based sensor designed for monitoring mechanical stresses at the stump-socket inter- face of lower-limb amputees is described. It provides practical means of measuring pressure and shear stresses simultaneously. In particular, it comprises of a flexible frame (20 mm × 20 mm), with thickness of 4 mm. By employing rapid prototyping technology in its fabrication, it offers a low-cost and versatile solution, with capability of adopting bespoke shapes of lower-limb residua. The sensor was first ana- lysed using finite element analysis (FEA) and then evaluated using lab-based electromechanical tests. The results validate that the sensor is capable of monitoring both pressure and shear at stresses up to 350 kPa and 80 kPa, respectively. A post-signal processing model is developed to induce pressure and shear stresses, respectively. The effective separation of pressure and shear signals can be potentially advantageous for sensor calibration in clinical applications. The sensor also demonstrates high linearity (approx. 5-8%) and high pressure (approx. 1.3 kPa) and shear (approx. 0.6 kPa) stress resolution perfor- mance. Accordingly, the sensor offers the potential for exploitation as an assistive tool to both evaluate prosthetic socket fitting in clinical settings and alert amputees in home settings of excessive loading at the stump-socket interface, effectively preventing stump tissue breakdown at an early stage.
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paper_title: Interface mechanics in external prosthetics: review of interface stress measurement techniques

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Instrumentation to measure accurately the stresses at the interface of a residual limb and prosthetic socket has a strong potential for use in prosthetic treatment. As a tool in the clinical setting, the device would allow a clinician to identify sites of excessive loading, information which could then be combined with clinical assessment of skin quality to determine regions of potential skin breakdown. Stress distributions for different prosthetic designs could be compared, facilitating a clinician's judgement to determine the optimal design for a patient. The instrumentation would have additional use in research as an evaluation tool for computer-based finite-element (FE) models. Stump-socket FE models predict stress distributions for proposed socket designs, thus offering advantages over interface stress measurement because evaluation can be conducted before a prosthesis is fabricated or put on an amputee patient. However, FE models must first be proven valid against experimental measurements before they can be considered accurate predictors of interface stresses. Current interface stress measurement techniques are described, with a concentration on a physical explanation of the advantages and limitations with each technique. New emerging technologies are discussed which are instruments that have been described but for which no data collected on amputees have been reported in the literature. The important new features of those technologies are also discussed.
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paper_title: Engineering a trans-tibial prosthetic socket for the lower limb amputee.

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INTRODUCTION ::: This review addresses the different prosthetic socket designs for trans-tibial amputees, the biomechanics behind the designs and the current state of the field. Of particular focus is the classic patella-tendon bearing (PTB) socket and the more recent sockets manufactured using pressure casting techniques and the theory, biomechanics and clinical implications of the two designs. Methods to examine and compare these designs are also addressed. ::: ::: ::: MATERIALS AND METHODS ::: Journal papers by various investigators which have clinical significance/impact on the field of trans-tibial socket design were chosen for this review. Articles were chosen over a period of over 50 years to demonstrate the evolution of knowledge. ::: ::: ::: RESULTS ::: The engineering of the trans-tibial socket has been largely subjected to empirical derivations and biomechanical theory that remains, for the most part, unproven. The fundamental principles of the PTB socket have been widely refuted. Hydrostatic theory based on pressure casting techniques, on the other hand, provides an optimal scenario to produce a more uniform stump/socket interface pressure. ::: ::: ::: CONCLUSION ::: Preliminary studies indicate the pressure casting technique has the potential to produce comfortable sockets, providing an alternative to the PTB design. Various studies have been attempted to quantitatively compare the 2 types of socket designs. However, further quantitative biomechanical studies are needed to explain the fundamental theory surrounding the pressure cast technique. Methods that could help further understand the pressure cast concept include amputee gait analysis, stump/socket interface pressure measurements, computer aided socket design and finite element modelling techniques.
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paper_title: Who is at risk of limb loss and what to do about it?

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Lower limb amputations were performed on over 105,000 individuals in United States short-stay hospitals between 1989 and 1992. Additional amputations were performed in VA, military, Indian Health, and charitable orthopaedic hospitals. Half of all lower extremity amputations occurred in individuals with diabetes. When the causal chain leading to diabetic amputations was examined in 80 consecutive patients at the VA Medical Center, Seattle, WA, 23 unique pathways were identified. Multiple pathway components were identified for 96% of patients, while in 4% a single ischemic pathway was sufficient in itself to require amputation. The majority of the scenarios leading to amputation began when patients with absent peripheral sensation sustained a pivotal event that initiated the causal chain to amputation. In nearly half the patients, this event was foot-wear-related. The pivotal event was followed by ulceration and faulty wound healing in 73% of patients. Each year thousands of individuals with diabetes undergo amputation in VA facilities, resulting in substantial cost to the Department of Veterans Affairs and to themselves. If the VA is to address the prevention or delay of limb loss, the causal pathway information indicates that attention to the footwear of diabetic patients is necessary.
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paper_title: Pressure distribution at the stump/socket interface in transtibial amputees during walking on stairs, slope and non-flat road.

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BACKGROUND ::: Studies examining the stump/socket interface stresses have been restricted to unsupported stance and natural gait, i.e. walking at a comfortable speed on flat and straight walkway. However, the pressure behaviour as to the interface in unilateral transtibial amputees during walking on stairs, slope and non-flat road is unclear. ::: ::: ::: METHODS ::: Pressure distribution changes at multiple points, expressed as mean peak stump/socket interface pressure, mean pressure level over 90% of peak pressure, time in which pressure exceeded 90% of peak pressure and time-pressure integral at the period of sustained sub-maximal load, were measured during natural ambulating and walking on stairs, slope and non-flat road. ::: ::: ::: FINDINGS ::: Compared with natural gait, the mean peak pressure and sustained sub-maximal load increase notably over the patellar tendon during walking on stairs and non-flat road, and however decrease or change insignificantly at the patellar tendon on slope and over other measured areas in all conditions; moreover the time period of sustained sub-maximal load changes remarkably, except over the patellar tendon during walking up slope and over the popliteal area on non-flat road; finally, the time-pressure integral in the time period of sustained sub-maximal load changes considerably, except at the patellar tendon during walking up slope. ::: ::: ::: INTERPRETATION ::: The pressure characteristics during natural ambulating seem not to be highly predictive of what occurs in the conditions of walking on stairs, slope and non-flat road, which leads to significant increase in amplitude domain of tissue loading only at the patellar tendon, and however to remarkable changes in temporal sequences of tissue (un-)loading almost in all measured regions.
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paper_title: A proposal for the pre‐evaluation protocol of below‐knee socket design - integration pain tolerance with finite element analysis

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Abstract The design of a fitted socket is a fundamental critical issue in ameliorating the disability of an amputee. In this study, an evaluation protocol integrated finite element analysis with the pain‐pressure‐tolerance (PPT) of soft‐tissue, is proposed to provide a quantitative socket design guideline prior to the socket being fabricated. A subject using a Kondylen‐Bettung‐Munster socket was selected in this study. Two FE models (the original Kondylen‐Bettung‐Munster and a newly designed total‐surface bearing socket) were established based on computer tomography images. The surface‐ to‐surface contact elements were employed to simulate the contact and sliding behaviors at the stump‐socket interface. The PPT of the soft‐tissue was measured by a hand‐held indentor system. Comparing the simulated peak interface pressure with the PPT, both sockets demonstrated a safe margin (PPT / peak interface pressure) greater than two. These large safe margin values were consistent with the subjective assessment, as a...
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paper_title: An Experimental and Theoretical Framework for Manufacturing Prosthetic Sockets for Transtibial Amputees

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Selective laser sintering (SLS) is a powerful manufacturing technology that does not require part-specific tooling or significant human intervention and provides the ability to easily generate parts with complex geometric designs. The present work focuses on developing a manufacturing framework using this technology to produce subject-specific transtibial amputee prosthetic sockets made of Duraform PA, which is a nylon-based material. The framework includes establishing an overall socket design (using the patellar-tendon bearing approach), performing a structural analysis using the finite element method (FEM) to ensure structural reliability during patient use, and validating the results by comparing the model output with experimental data. The validation included quantifying the failure conditions for the socket through a series of bending moment and compression tests. In the case study performed, the FEM results were within 3% of the experimental failure loads for the socket and were considered satisfactory
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paper_title: Quantification of prosthetic outcomes: elastomeric gel liner with locking pin suspension versus polyethylene foam liner with neoprene sleeve suspension.

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For this randomized crossover trial, we compared two common transtibial socket suspension systems: the Alpha liner with distal locking pin and the Pe-Lite liner with neoprene suspension sleeve. Our original hypotheses asserted that increased ambulatory activity, wear time, comfort, and satisfaction would be found with the elastomeric suspension system. Thirteen subjects completed the study. Following 2.5-month accommodation to each condition, ambulatory activity was recorded (steps/minute for 2 weeks), and subjects completed three questionnaires specific to prosthesis use and pain: the Prosthesis Evaluation Questionnaire (PEQ), a Brief Pain Inventory (BPI) excerpt, and the Socket Comfort Score (SCS). Upon completion, subjects selected their favored system for continued use. Ten subjects preferred the Pe-Lite and three the Alpha. Subjects spent 82% more time wearing the Pe-Lite and took 83% more steps per day. Ambulatory intensity distribution did not differ between systems. No statistically significant differences were found in questionnaire results. Subject feedback for each system was both positive and negative.
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paper_title: Comparison of the effects of patellar tendon bearing and total surface bearing sockets on prosthetic fitting and rehabilitation

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Patellar tendon bearing (PTB) and total surface bearing (TSB) sockets have been used respectively in the prosthetic treatment of 20 trans-tibial amputees to investigate the effectiveness of both sockets on prosthetic fitting and rehabilitation. Data analysis showed that prostheses with TSB sockets were lighter than the prostheses with PTB sockets and better suspension was obtained from TSB prosthetic socket (p<0.05). It was also found that weight acceptance on the amputated side advanced to a more normal value with TSB prostheses (p<0.05). There was a statistically significant difference between the two socket types in walking and in other ambulation activities except sitting and standing up from a chair, in favour of the TSB socket (p<0.05). Consequently, due to the outcome of this study it can be said that TSB prosthetic sockets can be used effectively in the rehabilitation of trans-tibial amputees.
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paper_title: The patellar tendon bar! Is it a necessary feature?

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The purpose of this investigation was to vary the load on the patellar tendon bar and to study the subsequent effect this has on the pattern of the pressure distribution at the stump-socket interface. Ten male subjects from the Southern General Hospital in Glasgow, UK participated in this study. Measuring systems utilising strain gauge and electrohydraulic technologies were designed, developed and constructed to enable pressure measurements to be conducted. One transducer, the patellar tendon (PT) transducer, was attached to the patellar tendon bar of the socket such that the patellar tendon bar was capable of being translated by +/-10 mm towards or away from the tendon. The results of this study showed that the position of the patellar tendon bar had no significant effect on the pressure distribution around the socket indicating that it is an unnecessary feature, which, we propose, may be eliminated during manufacture of a trans-tibial socket.
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paper_title: Review of the Socket Design and Interface Pressure Measurement for Transtibial Prosthesis

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Socket is an important part of every prosthetic limb as an interface between the residual limb and prosthetic components. Biomechanics of socket-residual limb interface, especially the pressure and force distribution, have effect on patient satisfaction and function. This paper aimed to review and evaluate studies conducted in the last decades on the design of socket, in-socket interface pressure measurement, and socket biomechanics. Literature was searched to find related keywords with transtibial amputation, socket-residual limb interface, socket measurement, socket design, modeling, computational modeling, and suspension system. In accordance with the selection criteria, 19 articles were selected for further analysis. It was revealed that pressure and stress have been studied in the last decaeds, but quantitative evaluations remain inapplicable in clinical settings. This study also illustrates prevailing systems, which may facilitate improvements in socket design for improved quality of life for individuals ambulating with transtibial prosthesis. It is hoped that the review will better facilitate the understanding and determine the clinical relevance of quantitative evaluations.
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paper_title: Negative pressures during swing phase in below-knee prostheses with rubber sleeve suspension.

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Negative pressures in the small space between the distal stump and the below-knee prosthetic socket were measured during swing phase for a series of nine subjects. A molded rubber sleeve connecting the prosthesis and the thigh was found to enhance this effect so that suction suspension occurred during the entire swing phase. Deterioration of the suction occurred when the sleeve was intentionally pierced, and when other suspensions such as a suprapatellar cuff or thigh band were tested. The findings indicate that the total-contact socket, gel liner and elastic sleeve combine to create suction in the below-knee socket which improves overall comfort and function for the patient in using the prosthesis.
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paper_title: Multi-material design and 3D printing method of lower limb prosthetic sockets

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The paper shows a research activity aimed at integrating low cost industrial technologies in the design, test and manufacture of medical devices. This work focuses on lower limb prosthesis and in particular on the custom-fit component interacting with the residual limb, i.e. the socket. The process going from the 3D reconstruction of patients' limb to the manufacture of the socket by means of a 3D printer has been designed. Moreover, this must be as automatic as possible and should not require the presence of a design and simulation expert. This implied a deep involvement of physicians and orthopaedic technicians in order to embed rules and procedures in the system. The process is divided in three steps: design, test and manufacture. For each step some details are shown and at last some conclusions are drawn mainly concerning the challenge of multi-material 3D printing of the socket.
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paper_title: Prosthetic sockets fabrication using rapid prototyping technology

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The traditional way of making a prosthetic socket is by draping a heated thermoplastic sheet over the positive mould, or by applying layers of woven materials together with acrylic resins over the positive mould. This process is extremely labour intensive, and it usually takes two to three days to make one socket. This paper presents the development of a prosthetics Computer‐Aided‐Manufacturing (CAM) system that utilises Rapid Prototyping (RP) technology. The system reduces the socket making time from days to less than 4 h. Clinical and biomechanical studies are conducted to evaluate the comfort and fit of the new socket during gait. Preliminary investigation of the new socket shows that its functional characteristics are very similar to that of a traditional socket
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paper_title: An experimental study of the interface pressure profile during level walking of a new suspension system for lower limb amputees.

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BACKGROUND ::: Different suspension systems that are used within prosthetic devices may alter the distribution of pressure inside the prosthetic socket in lower limb amputees. This study aimed to compare the interface pressure of a new magnetic suspension system with the pin/lock and Seal-In suspension systems. ::: ::: ::: METHODS ::: Twelve unilateral transtibial amputees participated in the study. The subjects walked on a level walkway at a self-selected speed. The resultant peak pressure with the three different suspension systems was recorded using F-socket transducers. ::: ::: ::: FINDINGS ::: There were significant statistical differences between the three studied suspension systems. Pair-wise analyses revealed that the mean peak pressure (kPa) was lower with the magnetic system than it was with the pin/lock system over the anterior and posterior aspects during one gait cycle (89.89 vs. 79.26 and 47.22 vs. 26.01, respectively). Overall, the average peak pressure values were higher with the Seal-In system than they were with the new magnetic lock and pin/lock system. ::: ::: ::: INTERPRETATION ::: The new magnetic system might reduce the pressure within the prosthetic socket in comparison to the pin/lock and Seal-In system during one gait cycle. This is particularly important during the swing phase of gait and may reduce the pain and discomfort at the distal residual limb in comparison to the pin/lock system.
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paper_title: Pistoning assessment in lower limb prosthetic sockets

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Background: One of the main indicators of the suspension system efficiency in lower limb prostheses is vertical displacement or pistoning within the socket. Decreasing pistoning and introducing an effective system for evaluating pistoning could contribute to the amputees’ rehabilitation process.Objectives: The main objective of this study was to review existing research studies that examine the occurrence of pistoning in lower limb prosthesis with different techniques in static (standing) and dynamic (walking and jumping) positions.Study Design: Literature review.Methods: Keywords related to slippage, suspension, pistoning and vertical movement in lower limb prosthetics were used to search the literature available in PubMed, ScienceDirect, Web of Science and Google Scholar databases. Sixteen articles were selected for further analysis according to the selection criteria.Results: The following methods have been used to measure the occurrence of pistoning in prosthetic limbs: radiological methods, photograp...
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paper_title: Case Report: Variably Compliant Transtibial Prosthetic Socket Fabricated Using Solid Freeform Fabrication

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Achieving and maintaining a comfortable fit in a lower-limb prosthetic socket is an important goal to help ensure a successful rehabilitation. The purpose of this case study was to assess the performance of sockets with compliant features integrated into the socket wall to relieve in-socket pressure during transtibial amputee gait. Two sockets incorporating variably compliant areas over the fibula head and distal tibia were fabricated for a transtibial amputee. The two sockets were designed with different levels of compliance and were compared with a third more conventional socket without compliant areas. All three sockets were otherwise geometrically identical and were aligned identically to eliminate in-socket pressure differences due to alignment. The three sockets were fabricated using selective laser sintering, a form of solid freeform fabrication. The in-socket pressure measurements were acquired during normal walking. Tekscan F-Socket pressure sensors were attached to the amputee’s residual limb rather than to the socket wall, which made it possible to measure pressures in the same location on the residual limb upon change of socket. A Vicon motion capture system was used to match in-socket pressures to the subject’s gait cycle. The pressure measurements showed that the compliant socket peak pressures over the distal tibia and fibula head were similar for the two compliance levels and nearly 50% and 30% lower than the conventional socket pressures, respectively. This case study showed that selective laser sintering manufactured sockets with variably compliant regions holds great promise for reducing contact pressure in sensitive regions of the residual limb. (J Prosthet Orthot. 2008;20:1‐7.) KEY INDEXING TERMS: prosthetic socket, amputees, CAD, CAM, solid freeform fabrication T he most important aspect of a lower extremity transtibial prosthesis is the socket design. The socket introduces a new interface or a new joint between the human and the mechanical support system. The forces generated through the socket either by body weight or by gait have to be carried by the soft tissue of the residual limb, which when improperly loaded can lead to discomfort or skin breakdown. Ultimately, the design and fit of the socket is what determines patient acceptance, comfort, suspension, and energy expenditure. 1 Achieving and maintaining a comfortable and tissue-tolerant socket fit remains a significant clinical problem. This study explores the use of new manufacturing techniques to fabricate sockets with integrated compliant features specifically designed to improve comfort and fit of the prosthesis.
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paper_title: Literature review of the possible advantages of silicon liner socket use in trans-tibial prostheses

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The silicon liner socket has been used in the trans-tibial prosthesis since the 1980s. Silicon liner sockets are sleeves of silicon material that are rolled onto the stump and fix the prosthesis to it. The producers of the liners propagate many advantages in their use i.e. better suspension of the prosthesis, protection of the stump skin and improved cosmetic appearance. This review was performed to find objective documentation in the literature in support of the advantages in prosthetic fitting and use of silicon liners. A medline search was performed with the key words: “silicon liner socket, Icelandic Roll On Silicon Socket (ICEROSS), trans-tibial prosthesis, lower leg prosthesis and stump sockets”. Six articles remained after application of the selection criteria. In two studies clinical examination was done while in the rest questionnaires were used to collect data. The indication for amputation varied from vascular insufficiency, diabetes mellitus and infection to trauma. Most studies mentioned improved prosthetic suspension compared to the conventional supracondylar fitting. Also the walking performance improved with less use of walking aids. There were reports of positive but also negative effects on the skin such as excessive perspiration and itching. Patients had a general preference in prosthetic appearance in favour of the prosthesis with a silicon liner. Further research is needed with the use of objective clinical parameters and a homogenous study group objectively to find advantages in the use of the silicon liner socket in the trans-tibial prosthesis.
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paper_title: Quantitative and Qualitative Comparison of a New Prosthetic Suspension System with Two Existing Suspension Systems for Lower Limb Amputees

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OBJECTIVE: The objectives of this study were to compare the effects of a newly designed magnetic suspension system with that of two existing suspension methods on pistoning inside the prosthetic socket and to compare satisfaction and perceived problems among transtibial amputees. DESIGN: In this prospective study, three lower limb prostheses with three different suspension systems were fabricated for ten transtibial amputees. The participants used each of the three prostheses for 1 mo in random order. Pistoning inside the prosthetic socket was measured by motion analysis system. The Prosthesis Evaluation Questionnaire was used to evaluate satisfaction and perceived problems with each suspension system. RESULTS: The lowest pistoning motion was found with the suction system compared with the other two suspension systems (P < 0.05). The new suspension system showed peak pistoning values similar to that of the pin lock system (P = 0.086). The results of the questionnaire survey revealed significantly higher satisfaction rates with the new system than with the other two systems in donning and doffing, walking, uneven walking, stair negotiation, and overall satisfaction (P < 0.05). CONCLUSIONS: The new suspension system has the potential to be used as an alternative to the available suspension systems. The pistoning motion was comparable to that of the other two systems. The new system showed compatible prosthetic suspension with the other two systems (suction and pin lock). The satisfaction with donning and doffing was high with the magnetic system. Moreover, the subjects reported fewer problems with the new system.
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paper_title: Socket considerations for the patient with a transtibial amputation.

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This paper reviews the theory of transtibial prosthetic socket designs from a historic perspective to the present. The patella tendon bearing socket originated in 1959, and is the standard from which the new alternative socket designs have evolved. Although the patella tendon bearing socket is still the most commonly prescribed socket for a transtibial prosthesis, the total surface bearing and hydrostatic sockets are becoming increasingly accepted. The total surface bearing socket still may incorporate the weightbearing characteristics of the patella tendon bearing socket, but often will be accompanied by a shock absorbing gel liner. The hydrostatic socket does not incorporate the standard patella tendon bearing design characteristics, but instead depends on a method of pressure casting that in theory produces a socket with equally distributed pressure over all of the residual limb soft tissue. These three designs are reviewed as current options for the socket portion of the transtibial prosthesis.
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paper_title: Systematic review of effects of current transtibial prosthetic socket designs-Part 1: Qualitative outcomes.

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This review is an attempt to untangle the complexity of transtibial prosthetic socket fit, determine the most important characteristic for a successful fitting, and perhaps find some indication of whether a particular prosthetic socket type might be best for a given situation. Further, it is intended to provide directions for future research. We followed the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines and used medical subject headings and standard key words to search for articles in relevant databases. No restrictions were made on study design or type of outcome measure. From the obtained search results (n = 1,863), 35 articles were included. The relevant data were entered into a predefined data form that incorporated the Downs and Black risk of bias assessment checklist. Results for the qualitative outcomes (n = 19 articles) are synthesized. Total surface bearing sockets lead to greater activity levels and satisfaction in active persons with amputation, those with a traumatic cause of amputation, and younger persons with amputation than patellar tendon bearing sockets. Evidence on vacuum-assisted suction and hydrostatic sockets is inadequate, and further studies are much needed. To improve the scientific basis for prescription, comparison of and correlation between mechanical properties of interface material, socket designs, user characteristics, and outcome measures should be conducted and reported in future studies.
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paper_title: The ICEROSS concept: A discussion of a philosophy

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Prefabricated ICEROSS (Icelandic Roll On Silicone Socket) sockets have been in use in Iceland since early 1986. Use of custom-made silicone sockets began several years earlier, and a paper devoted to the subject was presented at the 1984 AOPA Assembly by the author of this article. The ICEROSS system is primarily used for suspension. At the same time the author believes it considerably improves the weight-bearing capability of the prosthesis and the interface between prosthesis and user. After being turned inside out and rolled over the stump, the silicone sleeve forces skin in a distal direction, stabilising soft tissue and minimising pistoning. Both prosthetist and user may experience some problems initially, although most can be overcome by careful socket design and skin care.
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paper_title: The patellar-tendon-bearing prosthesis for below-knee amputees, a review of technique and criteria.

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At a recent meeting of the Workshop Panel on LowerExtremity Fitting (2), which is sponsored by the Sub­ committee on Design and Development of the Committee on Prosthetics Research and Development, there was pro­ longed discussion of below-knee prostheses. Questions were raised concerning the adequacy of the PTB design for many patients, especially patients who were longtime users of the joint-corset, below-knee limb. The view was expressed that the expenditures of time and money in achieving a successful PTB fit did not justify the selection of the PTB prosthesis or a conversion to it, and that the use of a joint-corset prosthesis initially would shorten the prosthetic restoration process for most patients. It was recognized that the private practitioner is often
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paper_title: Below Knee Prosthetic Socket Designs and Suspension Systems

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The prosthetic socket must act as a customized connection between the residual limb’s surrounding tissues and the prosthetic components. The socket must be designed to control weight bearing, suspension, and ambulation stability. When making a below-the-knee socket, the prosthetist attempts to maximize loading and minimize displacements, such as vertical, transverse, or rotational. This article discusses the engineering designs or shapes of the two basic forms of below-the-knee prosthetic sockets used today.
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paper_title: Engineering a trans-tibial prosthetic socket for the lower limb amputee.

paper_content:

INTRODUCTION ::: This review addresses the different prosthetic socket designs for trans-tibial amputees, the biomechanics behind the designs and the current state of the field. Of particular focus is the classic patella-tendon bearing (PTB) socket and the more recent sockets manufactured using pressure casting techniques and the theory, biomechanics and clinical implications of the two designs. Methods to examine and compare these designs are also addressed. ::: ::: ::: MATERIALS AND METHODS ::: Journal papers by various investigators which have clinical significance/impact on the field of trans-tibial socket design were chosen for this review. Articles were chosen over a period of over 50 years to demonstrate the evolution of knowledge. ::: ::: ::: RESULTS ::: The engineering of the trans-tibial socket has been largely subjected to empirical derivations and biomechanical theory that remains, for the most part, unproven. The fundamental principles of the PTB socket have been widely refuted. Hydrostatic theory based on pressure casting techniques, on the other hand, provides an optimal scenario to produce a more uniform stump/socket interface pressure. ::: ::: ::: CONCLUSION ::: Preliminary studies indicate the pressure casting technique has the potential to produce comfortable sockets, providing an alternative to the PTB design. Various studies have been attempted to quantitatively compare the 2 types of socket designs. However, further quantitative biomechanical studies are needed to explain the fundamental theory surrounding the pressure cast technique. Methods that could help further understand the pressure cast concept include amputee gait analysis, stump/socket interface pressure measurements, computer aided socket design and finite element modelling techniques.
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paper_title: Componentry for lower extremity prostheses.

paper_content:

Prosthetic components for both transtibial and transfemoral amputations are available for patients of every level of ambulation. Most current suspension systems, knees, foot/ankle assemblies, and shock absorbers use endoskeletal construction that emphasizes total contact and weight distribution between bony structures and soft tissues. Different components offer varying benefits to energy expenditure, activity level, balance, and proprioception. Less dynamic ambulators may use fixed-cadence knees and non-dynamic response feet; higher functioning walkers benefit from dynamic response feet and variable-cadence knees. In addition, specific considerations must be kept in mind when fitting a patient with peripheral vascular disease or diabetes.
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paper_title: Developments in the transtibial prosthetic socket fitting process: A review of past and present research

paper_content:

A revolution in trans-tibial prosthetic design began at the end of World War II with the development of new materials and a dramatic improvement in the understanding of biomechanics. Early research was based mainly on the improvement of existing prosthetic design practice. Today, research has been focused on providing a better understanding of stump/socket interface biomechanics and improving socket fit by attempting to quantify the normal/direct stresses at the interface. The purpose of this review paper is to question whether research and prosthetic education/training to date has significantly improved our understanding of what makes a good socket. Although there is no doubt that advances in socket fitting techniques have been made what is not clear is the actual extent to which these advances have improved the quality of sockets fitted. It is suggested that a new approach is needed which can overcome some of the inherent problems of designing and manufacturing a comfortable high quality socket. It is also suggested that current research and education/training in the fields of pressure/interfacial interaction measurement and Finite Element Analysis techniques have limited potential to address many of these problems. There is also little evidence that current computer aided design systems offer any significant advantages over more conventional techniques.
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paper_title: Standing interface stresses as a predictor of walking interface stresses in the trans-tibial prosthesis

paper_content:

Interface pressures and shear stresses within the socket, in standing and walking, were measured for two unilateral, male, trans-tibial amputee subjects, during two sessions each. The ratios of equal weight-bearing standing stresses to peak walking stresses showed regional variation, ranging from 0.24:1 for pressure over the anterior region to 1.01:1 for resultant interface shear stress over the lateral region. Interface stresses in standing were only moderate predictors of peak walking stresses. The best correlation coefficient between standing in full weight-bearing and peak walking stress was 0.88 for pressure over the lateral region. As the amputees progressed from minimal to full weight-bearing in standing, and then to walking, the interface stresses increased in a nonlinear fashion, consistent with the assumption that the anterior tibia provides much resistance to the bending moment in the sagittal plane during walking.
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paper_title: Measurement of stresses in three orthogonal directions at the residual limb-prosthetic socket interface

paper_content:

Transducers were developed to measure stresses in three orthogonal directions applied on a below-knee amputee residual limb within a prosthetic socket during walking. Strain-gage measurement techniques were used for all three orthogonal directions. Instrumentation error for four transducers averaged less than 4.2% full-scale output (FSO) for the normal direction and less than 0.9% FSO for shear directions. Measurements from amputee subjects collected during walking trials are presented. >
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paper_title: Static and dynamic pressure prediction for prosthetic socket fitting assessment utilising an inverse problem approach

paper_content:

Objective: It has been recognised in a review of the developments of lower-limb prosthetic socket fitting processes that the future demands new tools to aid in socket fitting. This paper presents the results of research to design and clinically test an artificial intelligence approach, specifically inverse problem analysis, for the determination of the pressures at the limb/prosthetic socket interface during stance and ambulation. Methods: Inverse problem analysis is based on accurately calculating the external loads or boundary conditions that can generate a known amount of strain, stresses or displacements at pre-determined locations on a structure. In this study a backpropagation artificial neural network (ANN) is designed and validated to predict the interfacial pressures at the residual limb/socket interface from strain data collected from the socket surface. The subject of this investigation was a 45-year-old male unilateral trans-tibial (below-knee) traumatic amputee who had been using a prosthesis for 22 years. Results: When comparing the ANN predicted interfacial pressure on 16 patches within the socket with actual pressures applied to the socket there is shown to be 8.7% difference, validating the methodology. Investigation of varying axial load through the subject's prosthesis, alignment of the subject's prosthesis, and pressure at the limb/socket interface during walking demonstrates that the validated ANN is able to give an accurate full-field study of the static and dynamic interfacial pressure distribution. Conclusions: To conclude, a methodology has been developed that enables a prosthetist to quantitatively analyse the distribution of pressures within the prosthetic socket in a clinical environment. This will aid in facilitating the ''right first time'' approach to socket fitting which will benefit both the patient in terms of comfort and the prosthetist, by reducing the time and associated costs of providing a high level of socket fit.
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paper_title: Stump/socket pressure profiles of the pressure cast prosthetic socket

paper_content:

Abstract Objective. The aim was to evaluate stump/socket interface pressure in amputees wearing a socket developed by a pressure casting system. Design. Five unilateral transtibial amputees wore a pressure cast socket and walked at a self-selected speed. Background. The socket produces equally distributed pressure at the stump/socket interface, deviating from the conventional belief that pressure varies in proportion to the pain threshold of different tissues in the stump. Methods. The socket was fabricated while the subject placed his stump in a pressure chamber. Pressure was applied while he adopted a normal standing position. A specially built strain gauged type pressure transducer was used for measuring pressure distribution. Pressure and gait parameters were measured simultaneously while the subjects were standing and walking. Results and conclusion. The pressure cast technique was able to provide comfortable fitting sockets. A hydrostatic pressure profile was not evident during standing or gait. Results also showed that no standard pressure profile for the pressure cast socket was observed. This was expected as no rectifications were done on the pressure cast socket. Pressure profiles at 10%, 25% and 50% of gait cycle did not correlate with the pressure profiles previously proposed. Relevance The hydrostatic theory is an attractive concept in socket design as it produces a stump/socket pressure profile that is evenly distributed. Furthermore, it is a method that is easily implemented, independent of a prosthetist’s skill and experience and reduces manufacturing time. However, there is still controversy surrounding the efficacy of this hydrostatic theory.
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paper_title: Stump-socket pressure in lower extremity prostheses

paper_content:

Abstract The pressures existent at the interface between stump and socket were obtained for two subjects equipped with above the knee prostheses. The effects of leg alignment changes and the passage of time are detailed in terms of local dynamic pressures experienced while walking. Local instantaneous pressures vary from 0 to 50 psi as a function of location, subject and gait phase. Highest pressures are obtained at the socket brim. Alignment changes produce but small pressure changes. Maximum donning pressures equal those in walking: standing pressures are less than half of peak walking pressures.
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paper_title: A review of prosthetic interface stress investigations.

paper_content:

Over the last decade, numerous experimental and numerical analyses have been conducted to investigate the stress distribution between the residual limb and prosthetic socket of persons with lower limb amputation. The objectives of these analyses have been to improve our understanding of the residual limb/prosthetic socket system, to evaluate the influence of prosthetic design parameters and alignment variations on the interface stress distribution, and to evaluate prosthetic fit. The purpose of this paper is to summarize these experimental investigations and identify associated limitations. In addition, this paper presents an overview of various computer models used to investigate the residual limb interface, and discusses the differences and potential ramifications of the various modeling formulations. Finally, the potential and future applications of these experimental and numerical analyses in prosthetic design are presented.
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paper_title: Predicting Interfacial Loads between the Prosthetic Socket and the Residual Limb for Below‐Knee Amputees – A Case Study

paper_content:

: In this study, an artificial neural network (ANN) was deployed as a tool to determine the internal loads between the residual limb and prosthetic socket for below-knee amputees. This was achieved by using simulated load data to validate the ANN and captured clinical load data to predict the internal loads at the residual limb–socket interface. Load/pressure was applied to 16 regions of the socket, using loading pads in conjunction with a load applicator, and surface strains were collected using 15 strain gauge rosettes. A super-position program was utilised to generate training and testing patterns from the original load/strain data collected. Using this data, a back-propagation ANN, developed at the University of the West of England, was trained. The input to the trained network was the surface strains and the output the internal loads/pressure. The system was validated and the mean square error (MSE) of the system was found to be 8.8% for 1000 training patterns and 8.9% for 50 testing patterns, which was deemed an acceptable error. Finally, the validated system was used to predict pressure-sensitive/-tolerant regions at the limb–socket interface with great success.
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paper_title: Stump-socket interface pressure as an aid to socket design in prostheses for trans-femoral amputees—a preliminary study

paper_content:

A system for measuring the stump-socket interface pressure was designed and built using a strain gauged type load cell. The system was utilized to study the pressure distribution in the quadrilateral and ischial containment type sockets. Two volunteer trans-femoral amputees fitted with both types of socket participated in the experiments. Pressures were measured while the subjects were standing and during walking. The maximum pressure recorded for standing was 34 kPa and for walking 95 kPa. Comparison made between the two sockets indicated that higher pressures were recorded at the proximal brim of the quadrilateral socket whereas the ischial containment socket produces a more evenly distributed pressure profile. The pressure distribution on the medial and lateral walls of both types of socket were similar but in the anterior and posterior walls, significant differences were noted. The results obtained from this study were compared with those found in published literature and the biomechanics of the two types of socket is discussed.
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paper_title: Remote monitoring of lower-limb prosthetic socket fit using wireless technologies.

paper_content:

Accurate fitting of a lower-limb prosthetic socket is the most important factor affecting amputee satisfaction and rehabilitation. The technology is now available to allow real-time monitoring of in-service pressure distribution of prosthetic limbs. This paper proposes a remote interfacial pressure monitoring system necessary for the assessment of fit. The suitability of a wireless ZigBee network due to its relevant technical specification is investigated. The system enables remote monitoring of a prosthetic socket and its fit under different operating conditions thereby improving design, efficiency and effectiveness. The data can be used by prosthetists and may also be recorded for future training or for patient progress monitoring. This can minimize the number of iterations by getting it right first time, thereby minimizing the number of replacement prostheses.
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paper_title: Review of the Socket Design and Interface Pressure Measurement for Transtibial Prosthesis

paper_content:

Socket is an important part of every prosthetic limb as an interface between the residual limb and prosthetic components. Biomechanics of socket-residual limb interface, especially the pressure and force distribution, have effect on patient satisfaction and function. This paper aimed to review and evaluate studies conducted in the last decades on the design of socket, in-socket interface pressure measurement, and socket biomechanics. Literature was searched to find related keywords with transtibial amputation, socket-residual limb interface, socket measurement, socket design, modeling, computational modeling, and suspension system. In accordance with the selection criteria, 19 articles were selected for further analysis. It was revealed that pressure and stress have been studied in the last decaeds, but quantitative evaluations remain inapplicable in clinical settings. This study also illustrates prevailing systems, which may facilitate improvements in socket design for improved quality of life for individuals ambulating with transtibial prosthesis. It is hoped that the review will better facilitate the understanding and determine the clinical relevance of quantitative evaluations.
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paper_title: A fiber Bragg grating quasi-distributed sensing network with a wavelength-tunable chaotic fiber laser

paper_content:

We propose a novel quasi-distributed sensing system using a wavelength-tunable chaotic fiber laser as well as identical weak fiber Bragg gratings (FBGs). FBG location is determined by measuring the time delay between the reference and the reflected chaotic light. The Bragg wavelength variety of a certain FBG, owing to the influence of external parameters, is scanned by a tunable chaotic fiber laser. The quasi-distributed sensing network is theoretically analyzed. Simulation results reveal hundreds of multiplexing capabilities and a spatial resolution of up to 1.3 cm.
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paper_title: High-speed internal strain measurements in composite structures under dynamic load using embedded FBG sensors

paper_content:

Internal strain measurements in cross-ply carbon-epoxy composite plates under dynamic loads are carried out using embedded FBG sensors. The principle of the FBG interrogation is based on intensity demodulation achieved via a Fabry-Perot filter. To account for the non-linearity of the filter, the system is calibrated and the amplitude of the strain data is validated. Strains are acquired at a rate of 100 kHz with a noise level as low as 2 μe and used for modal analysis and strain monitoring in low energy impact. The experimental results under impact and modal analysis compare very well with pertinent numerical models and modal analysis obtained from laser vibrometer measurements.
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paper_title: Wheatstone Bridge - The Basic Circuit for Strain Gauge Force Transducers

paper_content:

The strain gauge bonded on the elastic element is a secondary sensor which converts the strain produced by the force applied on the primary element into a resistance change. The classic configuration associated to the strain gauges is the low-power, Wheatstone bridge [18.1] – [18.4].
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paper_title: Tangential pressure measurements in above-knee suction sockets.

paper_content:

Tangential pressure (TP) , as defined in this study, is that pressure parallel to and located at the socket inner face. The talrgential pressure resultant (TP,) will possess a horizontal component (TP,) directed along an axis perpendicular to the main socket axis and a vertical component (TP,) directed along the main socket axis (see Fig. 1). The plane in which all tangential pressures exist is at right angles to the perpendicular pressure (PP) , i.e., squeeze pressure developed between the socket and the stump.
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paper_title: Measurement of stresses in three orthogonal directions at the residual limb-prosthetic socket interface

paper_content:

Transducers were developed to measure stresses in three orthogonal directions applied on a below-knee amputee residual limb within a prosthetic socket during walking. Strain-gage measurement techniques were used for all three orthogonal directions. Instrumentation error for four transducers averaged less than 4.2% full-scale output (FSO) for the normal direction and less than 0.9% FSO for shear directions. Measurements from amputee subjects collected during walking trials are presented. >
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paper_title: Considerations for development of sensing and monitoring tools to facilitate treatment and care of persons with lower-limb loss: A review

paper_content:

Sensing and monitoring technologies offer enormous potential to enhance the quality of healthcare provided to persons with lower-limb loss. Incorporation of these technologies into the rehabilitation process creates opportunities for a multidimensional exchange of timely, relevant, and meaningful health information between patients, their prostheses, and healthcare providers. Here, the authors envision a conceptual model for enhancing prosthetic rehabilitation through use of integrated physical and/or biological sensors and remote monitoring methods. Several specific applications that target treatment, diagnosis, and prognosis of health issues faced by persons with limb loss are proposed in an effort to demonstrate how collecting and using objective data can facilitate clinical decision making. Contemporary integrated sensors that may be used in these applications are reviewed and their limitations discussed. It is hoped that the considerations proposed here may serve to stimulate development of clinically useful monitoring and sensing technologies and promote their integration into routine amputation rehabilitation.
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paper_title: Clinical investigation of the pressure and shear stress on the trans-tibial stump with a prosthesis.

paper_content:

A system for measuring pressures and bi-axial shear stresses at the body support interfaces has been developed. This system has been used, in five unilateral trans-tibial amputees, to investigate the stresses at multiple points on the residual limb and prosthetic socket interface during standing and walking. The subjects investigated regularly used a patellar-tendon-bearing socket. The maximum peak pressure at the measured points was 320 kPa over the popliteal area during walking. The maximum shear stress was 61 kPa over the medial tibia area. Variable wave-forms of stress during walking were observed at the different measured points. The influence of the angular alignment on the stresses was investigated on one subject. It was found that a miss-alignment of +/- 8 degrees produced a change in peak longitudinal shear stress of between 8% and 11.5%.
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paper_title: The patellar tendon bar! Is it a necessary feature?

paper_content:

The purpose of this investigation was to vary the load on the patellar tendon bar and to study the subsequent effect this has on the pattern of the pressure distribution at the stump-socket interface. Ten male subjects from the Southern General Hospital in Glasgow, UK participated in this study. Measuring systems utilising strain gauge and electrohydraulic technologies were designed, developed and constructed to enable pressure measurements to be conducted. One transducer, the patellar tendon (PT) transducer, was attached to the patellar tendon bar of the socket such that the patellar tendon bar was capable of being translated by +/-10 mm towards or away from the tendon. The results of this study showed that the position of the patellar tendon bar had no significant effect on the pressure distribution around the socket indicating that it is an unnecessary feature, which, we propose, may be eliminated during manufacture of a trans-tibial socket.
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paper_title: A review of tactile sensing technologies with applications in biomedical engineering

paper_content:

Abstract Any device which senses information such as shape, texture, softness, temperature, vibration or shear and normal forces, by physical contact or touch, can be termed a tactile sensor. The importance of tactile sensor technology was recognized in the 1980s, along with a realization of the importance of computers and robotics. Despite this awareness, tactile sensors failed to be strongly adopted in industrial or consumer markets. In this paper, previous expectations of tactile sensors have been reviewed and the reasons for their failure to meet these expectations are discussed. The evolution of different tactile transduction principles, state of art designs and fabrication methods, and their pros and cons, are analyzed. From current development trends, new application areas for tactile sensors have been proposed. Literature from the last few decades has been revisited, and areas which are not appropriate for the use of tactile sensors have been identified. Similarly, the challenges that this technology needs to overcome in order to find its place in the market have been highlighted.
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paper_title: Stump/socket pressure profiles of the pressure cast prosthetic socket

paper_content:

Abstract Objective. The aim was to evaluate stump/socket interface pressure in amputees wearing a socket developed by a pressure casting system. Design. Five unilateral transtibial amputees wore a pressure cast socket and walked at a self-selected speed. Background. The socket produces equally distributed pressure at the stump/socket interface, deviating from the conventional belief that pressure varies in proportion to the pain threshold of different tissues in the stump. Methods. The socket was fabricated while the subject placed his stump in a pressure chamber. Pressure was applied while he adopted a normal standing position. A specially built strain gauged type pressure transducer was used for measuring pressure distribution. Pressure and gait parameters were measured simultaneously while the subjects were standing and walking. Results and conclusion. The pressure cast technique was able to provide comfortable fitting sockets. A hydrostatic pressure profile was not evident during standing or gait. Results also showed that no standard pressure profile for the pressure cast socket was observed. This was expected as no rectifications were done on the pressure cast socket. Pressure profiles at 10%, 25% and 50% of gait cycle did not correlate with the pressure profiles previously proposed. Relevance The hydrostatic theory is an attractive concept in socket design as it produces a stump/socket pressure profile that is evenly distributed. Furthermore, it is a method that is easily implemented, independent of a prosthetist’s skill and experience and reduces manufacturing time. However, there is still controversy surrounding the efficacy of this hydrostatic theory.
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paper_title: Interface pressure and shear stress changes with amputee weight loss: Case studies from two trans-tibial amputee subjects

paper_content:

Interface pressures and shear stresses were measured at monthly intervals on two transtibial amputee subjects who lost more than 12% of their body weight over the course of the study. For one subject interface pressures and shear stresses during the weight-acceptance phase of gait decreased over the study interval at all 13 sites monitored, while the other subject experienced increased pressures distally but decreased pressures proximally. Subjects' stumps appeared to atrophy over the study interval, increasing distal end and patellar tendon loading, but not increasing interface shear stresses at other locations. Adding socks at the end of the study did not return interface pressures to first session values at all sites. It is expected that local stump shape changes occurred, causing a non-uniform change in interface stress patterns.
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paper_title: Transducers for the determination of the pressure and shear stress distribution at the stump—socket interface of trans-tibial amputees

paper_content:

Recent developments in prosthetic socket design have created renewed interest in monitoring the stress distribution at the socket-residual limb interface. Although a few devices for measuring pressure can be found in the literature, none are capable of measuring reliably in areas of high curvature, such as the important area at the patellar tendon bar. Furthermore, few devices can record shear stress, thought to be critical in causing tissue damage. In order to address these issues two new transducers have been designed and evaluated. One design allows the simultaneous recording of the normal and shear stresses at various points of the socket walls, while the other is capable of measuring the three components of the force applied on the patellar tendon. The latter design incorporates a feature that permits displacement of the patellar tendon bar, in order to study the effect of various amounts of indentation of the tendon on the stress distribution around the residual limb. Both transducers were calibrated using dead weights and special jigs to ensure accurate loading conditions. Under laboratory bench conditions the normal-shear force transducer showed: 2.03 per cent full scale output (FSO) hysteresis error for shear stress direction, 1.65 per cent FSO for normal direction; 99.56 per cent FSO overall accuracy for shear direction, and within 99.64 per cent FSO for normal direction; and for the patellar tendon transducer 1.53 per cent FSO hysteresis error for shear direction, 1.85 per cent FSO for shear stress direction; 99.65 per cent FSO overall accuracy for shear direction, and 99.58 per cent FSO for normal direction. During an amputee walking trial the transducers showed 92 per cent to 97 per cent repeatability. The two new transducers were used in conjunction with two other types of transducers, previously designed at the University of Strathclyde, in a series of tests on ten trans-tibial amputees. Sample results for walking activities and a summary of maximum stresses recorded are presented.
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paper_title: Stump-socket pressure in lower extremity prostheses

paper_content:

Abstract The pressures existent at the interface between stump and socket were obtained for two subjects equipped with above the knee prostheses. The effects of leg alignment changes and the passage of time are detailed in terms of local dynamic pressures experienced while walking. Local instantaneous pressures vary from 0 to 50 psi as a function of location, subject and gait phase. Highest pressures are obtained at the socket brim. Alignment changes produce but small pressure changes. Maximum donning pressures equal those in walking: standing pressures are less than half of peak walking pressures.
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paper_title: Optical Fibre Pressure Sensors in Medical Applications

paper_content:

This article is focused on reviewing the current state-of-the-art of optical fibre pressure sensors for medical applications. Optical fibres have inherent advantages due to their small size, immunity to electromagnetic interferences and their suitability for remote monitoring and multiplexing. The small dimensions of optical fibre-based pressure sensors, together with being lightweight and flexible, mean that they are minimally invasive for many medical applications and, thus, particularly suited to in vivo measurement. This means that the sensor can be placed directly inside a patient, e.g., for urodynamic and cardiovascular assessment. This paper presents an overview of the recent developments in optical fibre-based pressure measurements with particular reference to these application areas.
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paper_title: Static and dynamic pressure profiles of a patellar-tendon-bearing (PTB) socket

paper_content:

AbstractThe purpose of this study was to evaluate the pressure distribution at the stump/socket interface in amputees wearing the patellar-tendon-bearing socket. A specially built strain gauged type pressure transducer was used for measuring this pressure distribution in four unilateral transtibial amputees. Pressure and gait parameters were measured simultaneously while they were standing and walking. Pressure profiles were compiled at 10, 25 and 50 per cent of gait cycle and compared with the pressure profiles predicted by Radcliffe in 1961. The subject's anterior-posterior pressure profiles were different from each other. However, at toe-off, each subject exhibited an increase in pressure at the patellar tendon. Their medial-lateral pressure profiles were similar: exhibiting high pressure at the medial proximal and lateral distal regions except for one subject who exhibited high pressure at the lateral proximal region instead. The subjects' pressure profiles did not resemble Radcliffe's anticipated pre...
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paper_title: Interface mechanics in external prosthetics: review of interface stress measurement techniques

paper_content:

Instrumentation to measure accurately the stresses at the interface of a residual limb and prosthetic socket has a strong potential for use in prosthetic treatment. As a tool in the clinical setting, the device would allow a clinician to identify sites of excessive loading, information which could then be combined with clinical assessment of skin quality to determine regions of potential skin breakdown. Stress distributions for different prosthetic designs could be compared, facilitating a clinician's judgement to determine the optimal design for a patient. The instrumentation would have additional use in research as an evaluation tool for computer-based finite-element (FE) models. Stump-socket FE models predict stress distributions for proposed socket designs, thus offering advantages over interface stress measurement because evaluation can be conducted before a prosthesis is fabricated or put on an amputee patient. However, FE models must first be proven valid against experimental measurements before they can be considered accurate predictors of interface stresses. Current interface stress measurement techniques are described, with a concentration on a physical explanation of the advantages and limitations with each technique. New emerging technologies are discussed which are instruments that have been described but for which no data collected on amputees have been reported in the literature. The important new features of those technologies are also discussed.
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paper_title: Changes in interface pressures and shear stresses over time on trans-tibial amputee subjects ambulating with prosthetic limbs: comparison of diurnal and six-month differences.

paper_content:

For trans-tibial amputees maintenance over time of a quality fit of the prosthesis to the residual limb is an important clinical challenge. The purpose of this research was to compare diurnal and long-term (5 weeks to 6 months) interface stress changes as well as variance in the change in cross-sectional area down the length of the residual limb. If long-term changes were simply accentuated diurnal fluctuations then this result would suggest similar treatment methods should be used for both conditions. Interface pressures and shear stresses at 13 sites and residual limb shape were measured on eight trans-tibial amputee subjects using patellar-tendon-bearing prostheses. Data were collected at diurnal intervals (within the same day at least 5 h apart) as well as at long-term intervals (5, 10, 15, 20, and 25 weeks apart). Absolute diurnal interface stress changes were not significantly different from those at 5-weeks intervals but were significantly smaller than those at 15, 20, and 25-weeks intervals. Mean interface stress changes increased significantly (p<0.05) for increased session-to-session intervals. Variance of the change in cross-sectional area down the length of the residual limb was significantly smaller for diurnal intervals than for 6-months intervals, indicating that long-term changes were more localized than diurnal changes. These results indicate that long-term changes are not simply accentuated diurnal fluctuations, suggesting that different treatment methods should be used to treat each condition.
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paper_title: Triaxial force transducer for investigating stresses at the stump/socket interface

paper_content:

Although normal pressures at the stump socket interface of the lower-limb amputee have been investigated, little is known about the shear stresses that also occur. Studies suggest that the combination of both shear and normal stresses significantly exacerbates discomfort and vascular and tissue damage. A means of simultaneously measuring normal and shear stresses will aid in the investigation and improvement of prosthetic fit. A miniature triaxial force transducer (4.9 x 16 mm diameter) has been developed which can be recessed into the socket wall. The principle of operation, construction, performance and limitations of the device are described. Preliminary measurements of the interface stress variations over the gait cycle in a supra-condylar PTB socket are presented. These show clear differences in the stress patterns present when two different prosthetic feet are used.
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paper_title: Development and preliminary testing of a device for the direct measurement of forces and moments in the prosthetic limb of transfemoral amputees during activities of daily living

paper_content:

Abstract ::: Purpose. To provide a comprehensive description of the direct measurement of forces and moments applied on the socket of transfemoral amputees during daily living activities. Methods. The forces and the moments applied on the socket of one female transfemoral amputee were measured with a commercial transducer at a sampling frequency of 200 Hz and recorded at distance using a wireless modem to transmit the data. The subject was asked to walk in a straight line and around a circle as well as to ascend and to descend a slope and stairs. The subject was instructed to perform each activity at her natural pace and as she would usually perform it during daily life. ::: Results. The results were based on a high number of gait cycles of the prosthetic leg for each activity. For instance, 62 gait cycles were measured during level walking in a straight line. Ascending a slope produced a larger moment around the medio-lateral axis than walking over the entire support phase. Also, walking around a circle produced a higher moment about the long axis of the socket than walking during the push off phase of the support. The mean stride frequency during descending a slope was higher than straight level walking. All the other activities presented a slower mean stride frequency than straight level walking. The impulse on the three axes was similar or smaller than walking in a straight line for all of the activities except for walking around a circle on the medio-lateral axis, as well as ascending a slope and stairs and walking around a circle on the long axis. ::: Conclusion. An apparatus to directly measure the actual forces and moments applied to the socket of the transfemoral amputees during an unlimited number of steps and a wide range of activities is presented. The apparatus presented here could be largely used by multi-disciplinary teams including engineers, prosthetists and physiotherapists facing the challenge of safely restoring the locomotion of transfemoral amputees fitted with a conventional socket or osseointegrated implant in particular.
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paper_title: Tangential pressure measurements in above-knee suction sockets.

paper_content:

Tangential pressure (TP) , as defined in this study, is that pressure parallel to and located at the socket inner face. The talrgential pressure resultant (TP,) will possess a horizontal component (TP,) directed along an axis perpendicular to the main socket axis and a vertical component (TP,) directed along the main socket axis (see Fig. 1). The plane in which all tangential pressures exist is at right angles to the perpendicular pressure (PP) , i.e., squeeze pressure developed between the socket and the stump.
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paper_title: Hybrid resistive tactile sensing

paper_content:

The paper describes a novel design of a robot tactile sensor, called hybrid tactile sensor, based on analog resistive technology. The design employs a set of parallel analog resistive sensing strips, rather than a two-dimensional (2D) grid of sensing elements, to sample the sensor surface. It is therefore analog in one dimension and discrete in the other. As a result, the number of samples that need to be obtained is significantly reduced, as is the number of connectors in the sensor circuitry. In addition, the sensor design scales easily to a large sensing surface area, and offers flexibility in sensor geometry. However, only the contact location and shape can be sensed, but not the contact force. The paper provides the theoretical model of the sensor, and presents simulation and experimental results.
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paper_title: Calibration problems encountered while monitoring stump/socket interface pressures with force sensing resistors: Techniques adopted to minimise inaccuracies

paper_content:

Force sensing resistors (FSR) have been used to measure dynamic pressures at the interface between appliance and patient. Inaccuracies using FSRs have been reported. This paper summarises both the calibration problems encountered and the techniques adopted to minimise inaccuracies. It is considered that, by calibrating the transducers attached to the socket, and by adopting a strict test protocol, FSRs may provide a guide to the dynamic pressure distribution applied to the trans-tibial stump during gait.
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paper_title: Measurement of stresses in three orthogonal directions at the residual limb-prosthetic socket interface

paper_content:

Transducers were developed to measure stresses in three orthogonal directions applied on a below-knee amputee residual limb within a prosthetic socket during walking. Strain-gage measurement techniques were used for all three orthogonal directions. Instrumentation error for four transducers averaged less than 4.2% full-scale output (FSO) for the normal direction and less than 0.9% FSO for shear directions. Measurements from amputee subjects collected during walking trials are presented. >
---
paper_title: Considerations for development of sensing and monitoring tools to facilitate treatment and care of persons with lower-limb loss: A review

paper_content:

Sensing and monitoring technologies offer enormous potential to enhance the quality of healthcare provided to persons with lower-limb loss. Incorporation of these technologies into the rehabilitation process creates opportunities for a multidimensional exchange of timely, relevant, and meaningful health information between patients, their prostheses, and healthcare providers. Here, the authors envision a conceptual model for enhancing prosthetic rehabilitation through use of integrated physical and/or biological sensors and remote monitoring methods. Several specific applications that target treatment, diagnosis, and prognosis of health issues faced by persons with limb loss are proposed in an effort to demonstrate how collecting and using objective data can facilitate clinical decision making. Contemporary integrated sensors that may be used in these applications are reviewed and their limitations discussed. It is hoped that the considerations proposed here may serve to stimulate development of clinically useful monitoring and sensing technologies and promote their integration into routine amputation rehabilitation.
---
paper_title: Pressures at the Residual Limb-Socket Interface in Transtibial Amputees with Thigh Lacer-Side Joints

paper_content:

ABSTRACTThe residual limb-socket interface pressures were measured in 13 transtibial amputees who use prostheses with side joints and thigh lacers. The hypothesis of this study was that the interface pressures with a thigh lacer are lower than the pressures without a thigh lacer. Comparison of the i
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paper_title: Microfabricated Tactile Sensors for Biomedical Applications: A Review

paper_content:

During the last decades, tactile sensors based on different sensing principles have been developed due to the growing interest in robotics and, mainly, in medical applications. Several technological solutions have been employed to design tactile sensors; in particular, solutions based on microfabrication present several attractive features. Microfabrication technologies allow for developing miniaturized sensors with good performance in terms of metrological properties (e.g., accuracy, sensitivity, low power consumption, and frequency response). Small size and good metrological properties heighten the potential role of tactile sensors in medicine, making them especially attractive to be integrated in smart interfaces and microsurgical tools. This paper provides an overview of microfabricated tactile sensors, focusing on the mean principles of sensing, i.e., piezoresistive, piezoelectric and capacitive sensors. These sensors are employed for measuring contact properties, in particular force and pressure, in three main medical fields, i.e., prosthetics and artificial skin, minimal access surgery and smart interfaces for biomechanical analysis. The working principles and the metrological properties of the most promising tactile, microfabricated sensors are analyzed, together with their application in medicine. Finally, the new emerging technologies in these fields are briefly described.
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paper_title: Clinical investigation of the pressure and shear stress on the trans-tibial stump with a prosthesis.

paper_content:

A system for measuring pressures and bi-axial shear stresses at the body support interfaces has been developed. This system has been used, in five unilateral trans-tibial amputees, to investigate the stresses at multiple points on the residual limb and prosthetic socket interface during standing and walking. The subjects investigated regularly used a patellar-tendon-bearing socket. The maximum peak pressure at the measured points was 320 kPa over the popliteal area during walking. The maximum shear stress was 61 kPa over the medial tibia area. Variable wave-forms of stress during walking were observed at the different measured points. The influence of the angular alignment on the stresses was investigated on one subject. It was found that a miss-alignment of +/- 8 degrees produced a change in peak longitudinal shear stress of between 8% and 11.5%.
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paper_title: Validation of F-scan pressure sensor system: A technical note

paper_content:

This study performed a quantitative validation on a recently developed pressure sensitive transducer system, the F-Scan sensor system. The results indicate that the sensor is adequate for determination of pressure distribution under contact conditions with soft materials. The linear response of the sensor was up to 1.7 MPa with good homogeneity throughout sensor cells. However, the sensor is sensitive to surface conditions, loading speeds, and temperature. Variations also exist from sensor to sensor. In order to have accurate measurement, calibration was recommended in actual clinical or experimental conditions prior to use, including surface contact conditions, loading speeds, and temperature environment. In addition, this sensor system is not suitable for hard surface contact such as plexiglas.
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paper_title: The patellar tendon bar! Is it a necessary feature?

paper_content:

The purpose of this investigation was to vary the load on the patellar tendon bar and to study the subsequent effect this has on the pattern of the pressure distribution at the stump-socket interface. Ten male subjects from the Southern General Hospital in Glasgow, UK participated in this study. Measuring systems utilising strain gauge and electrohydraulic technologies were designed, developed and constructed to enable pressure measurements to be conducted. One transducer, the patellar tendon (PT) transducer, was attached to the patellar tendon bar of the socket such that the patellar tendon bar was capable of being translated by +/-10 mm towards or away from the tendon. The results of this study showed that the position of the patellar tendon bar had no significant effect on the pressure distribution around the socket indicating that it is an unnecessary feature, which, we propose, may be eliminated during manufacture of a trans-tibial socket.
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paper_title: A review of tactile sensing technologies with applications in biomedical engineering

paper_content:

Abstract Any device which senses information such as shape, texture, softness, temperature, vibration or shear and normal forces, by physical contact or touch, can be termed a tactile sensor. The importance of tactile sensor technology was recognized in the 1980s, along with a realization of the importance of computers and robotics. Despite this awareness, tactile sensors failed to be strongly adopted in industrial or consumer markets. In this paper, previous expectations of tactile sensors have been reviewed and the reasons for their failure to meet these expectations are discussed. The evolution of different tactile transduction principles, state of art designs and fabrication methods, and their pros and cons, are analyzed. From current development trends, new application areas for tactile sensors have been proposed. Literature from the last few decades has been revisited, and areas which are not appropriate for the use of tactile sensors have been identified. Similarly, the challenges that this technology needs to overcome in order to find its place in the market have been highlighted.
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paper_title: Stump/socket pressure profiles of the pressure cast prosthetic socket

paper_content:

Abstract Objective. The aim was to evaluate stump/socket interface pressure in amputees wearing a socket developed by a pressure casting system. Design. Five unilateral transtibial amputees wore a pressure cast socket and walked at a self-selected speed. Background. The socket produces equally distributed pressure at the stump/socket interface, deviating from the conventional belief that pressure varies in proportion to the pain threshold of different tissues in the stump. Methods. The socket was fabricated while the subject placed his stump in a pressure chamber. Pressure was applied while he adopted a normal standing position. A specially built strain gauged type pressure transducer was used for measuring pressure distribution. Pressure and gait parameters were measured simultaneously while the subjects were standing and walking. Results and conclusion. The pressure cast technique was able to provide comfortable fitting sockets. A hydrostatic pressure profile was not evident during standing or gait. Results also showed that no standard pressure profile for the pressure cast socket was observed. This was expected as no rectifications were done on the pressure cast socket. Pressure profiles at 10%, 25% and 50% of gait cycle did not correlate with the pressure profiles previously proposed. Relevance The hydrostatic theory is an attractive concept in socket design as it produces a stump/socket pressure profile that is evenly distributed. Furthermore, it is a method that is easily implemented, independent of a prosthetist’s skill and experience and reduces manufacturing time. However, there is still controversy surrounding the efficacy of this hydrostatic theory.
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paper_title: Interface pressure and shear stress changes with amputee weight loss: Case studies from two trans-tibial amputee subjects

paper_content:

Interface pressures and shear stresses were measured at monthly intervals on two transtibial amputee subjects who lost more than 12% of their body weight over the course of the study. For one subject interface pressures and shear stresses during the weight-acceptance phase of gait decreased over the study interval at all 13 sites monitored, while the other subject experienced increased pressures distally but decreased pressures proximally. Subjects' stumps appeared to atrophy over the study interval, increasing distal end and patellar tendon loading, but not increasing interface shear stresses at other locations. Adding socks at the end of the study did not return interface pressures to first session values at all sites. It is expected that local stump shape changes occurred, causing a non-uniform change in interface stress patterns.
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paper_title: Transducers for the determination of the pressure and shear stress distribution at the stump—socket interface of trans-tibial amputees

paper_content:

Recent developments in prosthetic socket design have created renewed interest in monitoring the stress distribution at the socket-residual limb interface. Although a few devices for measuring pressure can be found in the literature, none are capable of measuring reliably in areas of high curvature, such as the important area at the patellar tendon bar. Furthermore, few devices can record shear stress, thought to be critical in causing tissue damage. In order to address these issues two new transducers have been designed and evaluated. One design allows the simultaneous recording of the normal and shear stresses at various points of the socket walls, while the other is capable of measuring the three components of the force applied on the patellar tendon. The latter design incorporates a feature that permits displacement of the patellar tendon bar, in order to study the effect of various amounts of indentation of the tendon on the stress distribution around the residual limb. Both transducers were calibrated using dead weights and special jigs to ensure accurate loading conditions. Under laboratory bench conditions the normal-shear force transducer showed: 2.03 per cent full scale output (FSO) hysteresis error for shear stress direction, 1.65 per cent FSO for normal direction; 99.56 per cent FSO overall accuracy for shear direction, and within 99.64 per cent FSO for normal direction; and for the patellar tendon transducer 1.53 per cent FSO hysteresis error for shear direction, 1.85 per cent FSO for shear stress direction; 99.65 per cent FSO overall accuracy for shear direction, and 99.58 per cent FSO for normal direction. During an amputee walking trial the transducers showed 92 per cent to 97 per cent repeatability. The two new transducers were used in conjunction with two other types of transducers, previously designed at the University of Strathclyde, in a series of tests on ten trans-tibial amputees. Sample results for walking activities and a summary of maximum stresses recorded are presented.
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paper_title: Stump-socket pressure in lower extremity prostheses

paper_content:

Abstract The pressures existent at the interface between stump and socket were obtained for two subjects equipped with above the knee prostheses. The effects of leg alignment changes and the passage of time are detailed in terms of local dynamic pressures experienced while walking. Local instantaneous pressures vary from 0 to 50 psi as a function of location, subject and gait phase. Highest pressures are obtained at the socket brim. Alignment changes produce but small pressure changes. Maximum donning pressures equal those in walking: standing pressures are less than half of peak walking pressures.
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paper_title: A review of prosthetic interface stress investigations.

paper_content:

Over the last decade, numerous experimental and numerical analyses have been conducted to investigate the stress distribution between the residual limb and prosthetic socket of persons with lower limb amputation. The objectives of these analyses have been to improve our understanding of the residual limb/prosthetic socket system, to evaluate the influence of prosthetic design parameters and alignment variations on the interface stress distribution, and to evaluate prosthetic fit. The purpose of this paper is to summarize these experimental investigations and identify associated limitations. In addition, this paper presents an overview of various computer models used to investigate the residual limb interface, and discusses the differences and potential ramifications of the various modeling formulations. Finally, the potential and future applications of these experimental and numerical analyses in prosthetic design are presented.
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paper_title: A traction stress sensor array for use in high-resolution robotic tactile imaging

paper_content:

A high resolution large-area array capable of resolving the three independent components of a 2D triaxial contact stress profile has been developed. The array, composed of 4096 (64/spl times/64) individual stress sensing elements, was constructed with a fully CMOS-compatible fabrication process, allowing integration of the sensing structures with digital control circuitry. The individual array elements have been shown to demonstrate linear responses to both applied normal stress (1.59 mV/kPa, 0-35 kPa) and applied shear stress (0.32 mV/kPa, 0-60 kPa). A spatial resolution comparable to the spacing of the papillary ridges of the human dermis (/spl ap/300 /spl mu/m) has been achieved within the 1.92/spl times/1.92 cm active sensing area of the array. Descriptions of the sensor structure, the required signal conditioning, and the array architecture are presented in this paper. The results of electrical and mechanical characterization studies are also outlined.
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paper_title: Properties of the flexible pressure sensor under laboratory conditions simulating the internal environment of the total surface bearing socket

paper_content:

The purpose of this study was to investigate the properties of the flexible pressure sensor under laboratory conditions simulating the internal environment of the total surface bearing (TSB) socket to determine optimal conditions for measuring normal stresses on the stump. The equipment used in the study was the Pressure Distribution Sensor System for Sockets. In a climatic chamber maintained at 37d`C and 70% humidity the sensor sheet was mounted on a measuring apparatus loaded with three 10 kg weights, and output from the sensor was records after loading was adopted as the measured output. Output was greater when weight was decreased than when weight was increased because of hysteresis (paired t-test, p p>0.05). There were no significant differences in output among five sensor sheets or among five sections of four sensor sheets (two-way ANOVA, p>0.05), but repeated loading on th...
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paper_title: Scientific validation of two commercial pressure sensor systems for prosthetic socket fit

paper_content:

The concept of measuring pressure at the interface between the stump and the prosthetic socket could provide valuable information in the process of prosthetic socket fabrication, modification, and fit. Two systems, the Rincoe Socket Fitting System (SFS) and Tekscan's F-Socket Pressure Measurement System, have been commercially designed for in situ interface pressure measurement over the past decade. Their use is not common in prosthetic practice, perhaps due to questions of cost effectiveness and the difficulties of interpreting the data. Another concern is the use of sensors for pressure measurements in areas of high contour and complex geometries such as the stump. Before these systems can be used in a clinical setting, it is necessary to determine the reliability and accuracy of each system. In order to assess the clinical validity of the Rincoe SFS and F-Socket systems, a series of trials was conducted to evaluate different aspects of sensor performance, namely; accuracy, hysteresis, drift and the effect of curvature. The sensors were subjected to tests in flatbed and custom-designed pressure vessels. Overall results indicated an accuracy error for the Rincoe SFS system of 25% (flatbed) and 33% (mould), with a corresponding 15% (flatbed) and 23% (mould) error in hysteresis, and 7% (flatbed) and 11% (mould) drift errors. The F-Socket system demonstrated an 8% (flatbed) and 11% (mould) accuracy errors, 42% (flatbed) and 24% (mould) hysteresis errors, and 12% (flatbed) and 33% (mould) drift errors. These findings indicate favourable results for the F-Socket Pressure Measurement System compared to the Rincoe Socket Fitting System with respect to its accuracy errors only. Nevertheless, it is the authors' belief that these systems are adequate in indicating areas of high pressure at the stump socket interface for clinical purposes, but both systems should be used with caution.
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paper_title: Static and dynamic pressure profiles of a patellar-tendon-bearing (PTB) socket

paper_content:

AbstractThe purpose of this study was to evaluate the pressure distribution at the stump/socket interface in amputees wearing the patellar-tendon-bearing socket. A specially built strain gauged type pressure transducer was used for measuring this pressure distribution in four unilateral transtibial amputees. Pressure and gait parameters were measured simultaneously while they were standing and walking. Pressure profiles were compiled at 10, 25 and 50 per cent of gait cycle and compared with the pressure profiles predicted by Radcliffe in 1961. The subject's anterior-posterior pressure profiles were different from each other. However, at toe-off, each subject exhibited an increase in pressure at the patellar tendon. Their medial-lateral pressure profiles were similar: exhibiting high pressure at the medial proximal and lateral distal regions except for one subject who exhibited high pressure at the lateral proximal region instead. The subjects' pressure profiles did not resemble Radcliffe's anticipated pre...
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paper_title: Interface mechanics in external prosthetics: review of interface stress measurement techniques

paper_content:

Instrumentation to measure accurately the stresses at the interface of a residual limb and prosthetic socket has a strong potential for use in prosthetic treatment. As a tool in the clinical setting, the device would allow a clinician to identify sites of excessive loading, information which could then be combined with clinical assessment of skin quality to determine regions of potential skin breakdown. Stress distributions for different prosthetic designs could be compared, facilitating a clinician's judgement to determine the optimal design for a patient. The instrumentation would have additional use in research as an evaluation tool for computer-based finite-element (FE) models. Stump-socket FE models predict stress distributions for proposed socket designs, thus offering advantages over interface stress measurement because evaluation can be conducted before a prosthesis is fabricated or put on an amputee patient. However, FE models must first be proven valid against experimental measurements before they can be considered accurate predictors of interface stresses. Current interface stress measurement techniques are described, with a concentration on a physical explanation of the advantages and limitations with each technique. New emerging technologies are discussed which are instruments that have been described but for which no data collected on amputees have been reported in the literature. The important new features of those technologies are also discussed.
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paper_title: Laboratory and clinical tests of a prototype pressure sensor for clinical assessment of prosthetic socket fit

paper_content:

Lower limb prosthetic socket fabrication is a highly refined process relying on the prosthetist's skill and experience. Despite their best efforts, patients often return with complications. Additionally, clinical application of technological advances for the quantification of biomechanical factors at the socket interface has not changed in practice. Measuring pressure levels at the stump/socket interface could provide valuable information in the process of prosthetic socket fabrication, fit and modification. This paper presents findings on the performance of a prototype capacitance pressure sensor designed for prosthetic socket use. Bench tests using compressed air were performed to measure accuracy, hysteresis and drift responses in both a flatbed chamber and a custommodified pressure vessel. For the contoured testing, the sensors were placed on nine sites on a positive trans-tibial stump mould and enveloped with a silicone liner. Additionally, a preliminary clinical evaluation was performed with two trans-tibial amputee subjects at the nine sites during normal ambulation. Bench test results showed that the prototype capacitance sensor performed well in all categories, exhibiting a 2.42% (flatbed) and 9.96% (contoured) accuracy error, a 12.93% (flatbed) and 12.95% (contoured) hysteresis error, and a 4.40% (flatbed) and 6.20% All correspondence to be addressed to Dr. Adrian A. Polliack, Senior Vice-President for Research,
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paper_title: Review: Semiconductor Piezoresistance for Microsystems

paper_content:

Piezoresistive sensors are among the earliest micromachined silicon devices. The need for smaller, less expensive, higher performance sensors helped drive early micromachining technology, a precursor to microsystems or microelectromechanical systems (MEMS). The effect of stress on doped silicon and germanium has been known since the work of Smith at Bell Laboratories in 1954. Since then, researchers have extensively reported on microscale, piezoresistive strain gauges, pressure sensors, accelerometers, and cantilever force/displacement sensors, including many commercially successful devices. In this paper, we review the history of piezoresistance, its physics and related fabrication techniques. We also discuss electrical noise in piezoresistors, device examples and design considerations, and alternative materials. This paper provides a comprehensive overview of integrated piezoresistor technology with an introduction to the physics of piezoresistivity, process and material selection and design guidance useful to researchers and device engineers.
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paper_title: Changes in interface pressures and shear stresses over time on trans-tibial amputee subjects ambulating with prosthetic limbs: comparison of diurnal and six-month differences.

paper_content:

For trans-tibial amputees maintenance over time of a quality fit of the prosthesis to the residual limb is an important clinical challenge. The purpose of this research was to compare diurnal and long-term (5 weeks to 6 months) interface stress changes as well as variance in the change in cross-sectional area down the length of the residual limb. If long-term changes were simply accentuated diurnal fluctuations then this result would suggest similar treatment methods should be used for both conditions. Interface pressures and shear stresses at 13 sites and residual limb shape were measured on eight trans-tibial amputee subjects using patellar-tendon-bearing prostheses. Data were collected at diurnal intervals (within the same day at least 5 h apart) as well as at long-term intervals (5, 10, 15, 20, and 25 weeks apart). Absolute diurnal interface stress changes were not significantly different from those at 5-weeks intervals but were significantly smaller than those at 15, 20, and 25-weeks intervals. Mean interface stress changes increased significantly (p<0.05) for increased session-to-session intervals. Variance of the change in cross-sectional area down the length of the residual limb was significantly smaller for diurnal intervals than for 6-months intervals, indicating that long-term changes were more localized than diurnal changes. These results indicate that long-term changes are not simply accentuated diurnal fluctuations, suggesting that different treatment methods should be used to treat each condition.
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paper_title: The effect of biomechanical variables on force sensitive resistor error: Implications for calibration and improved accuracy.

paper_content:

Force Sensitive Resistors (FSRs) are commercially available thin film polymer sensors commonly employed in a multitude of biomechanical measurement environments. Reasons for such wide spread usage lie in the versatility, small profile, and low cost of these sensors. Yet FSRs have limitations. It is commonly accepted that temperature, curvature and biological tissue compliance may impact sensor conductance and resulting force readings. The effect of these variables and degree to which they interact has yet to be comprehensively investigated and quantified. This work systematically assesses varying levels of temperature, sensor curvature and surface compliance using a full factorial design-of-experiments approach. Three models of Interlink FSRs were evaluated. Calibration equations under 12 unique combinations of temperature, curvature and compliance were determined for each sensor. Root mean squared error, mean absolute error, and maximum error were quantified as measures of the impact these thermo/mechanical factors have on sensor performance. It was found that all three variables have the potential to affect FSR calibration curves. The FSR model and corresponding sensor geometry are sensitive to these three mechanical factors at varying levels. Experimental results suggest that reducing sensor error requires calibration of each sensor in an environment as close to its intended use as possible and if multiple FSRs are used in a system, they must be calibrated independently.
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paper_title: Pressure Sensor: State of the Art, Design, and Application for Robotic Hand

paper_content:

We survey the state of the art in a variety of force sensors for designing and application of robotic hand. Most of the force sensors are examined based on tactile sensing. For a decade, many papers have widely discussed various sensor technologies and transducer methods which are based on microelectromechanical system (MEMS) and silicon used for improving the accuracy and performance measurement of tactile sensing capabilities especially for robotic hand applications. We found that transducers and materials such as piezoresistive and polymer, respectively, are used in order to improve the sensing sensitivity for grasping mechanisms in future. This predicted growth in such applications will explode into high risk tasks which requires very precise purposes. It shows considerable potential and significant levels of research attention.
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paper_title: Development and preliminary testing of a device for the direct measurement of forces and moments in the prosthetic limb of transfemoral amputees during activities of daily living

paper_content:

Abstract ::: Purpose. To provide a comprehensive description of the direct measurement of forces and moments applied on the socket of transfemoral amputees during daily living activities. Methods. The forces and the moments applied on the socket of one female transfemoral amputee were measured with a commercial transducer at a sampling frequency of 200 Hz and recorded at distance using a wireless modem to transmit the data. The subject was asked to walk in a straight line and around a circle as well as to ascend and to descend a slope and stairs. The subject was instructed to perform each activity at her natural pace and as she would usually perform it during daily life. ::: Results. The results were based on a high number of gait cycles of the prosthetic leg for each activity. For instance, 62 gait cycles were measured during level walking in a straight line. Ascending a slope produced a larger moment around the medio-lateral axis than walking over the entire support phase. Also, walking around a circle produced a higher moment about the long axis of the socket than walking during the push off phase of the support. The mean stride frequency during descending a slope was higher than straight level walking. All the other activities presented a slower mean stride frequency than straight level walking. The impulse on the three axes was similar or smaller than walking in a straight line for all of the activities except for walking around a circle on the medio-lateral axis, as well as ascending a slope and stairs and walking around a circle on the long axis. ::: Conclusion. An apparatus to directly measure the actual forces and moments applied to the socket of the transfemoral amputees during an unlimited number of steps and a wide range of activities is presented. The apparatus presented here could be largely used by multi-disciplinary teams including engineers, prosthetists and physiotherapists facing the challenge of safely restoring the locomotion of transfemoral amputees fitted with a conventional socket or osseointegrated implant in particular.
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paper_title: Microfabricated Tactile Sensors for Biomedical Applications: A Review

paper_content:

During the last decades, tactile sensors based on different sensing principles have been developed due to the growing interest in robotics and, mainly, in medical applications. Several technological solutions have been employed to design tactile sensors; in particular, solutions based on microfabrication present several attractive features. Microfabrication technologies allow for developing miniaturized sensors with good performance in terms of metrological properties (e.g., accuracy, sensitivity, low power consumption, and frequency response). Small size and good metrological properties heighten the potential role of tactile sensors in medicine, making them especially attractive to be integrated in smart interfaces and microsurgical tools. This paper provides an overview of microfabricated tactile sensors, focusing on the mean principles of sensing, i.e., piezoresistive, piezoelectric and capacitive sensors. These sensors are employed for measuring contact properties, in particular force and pressure, in three main medical fields, i.e., prosthetics and artificial skin, minimal access surgery and smart interfaces for biomechanical analysis. The working principles and the metrological properties of the most promising tactile, microfabricated sensors are analyzed, together with their application in medicine. Finally, the new emerging technologies in these fields are briefly described.
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paper_title: Design, development, and characteristics of an in-shoe triaxial pressure measurement transducer utilizing a single element of piezoelectric copolymer film

paper_content:

In gait analysis, there is growing awareness of the need to simultaneously measure shear and vertical forces for the diagnosis and treatment assessment of pathological foot disorders. This is especially the case in the measurement of the forces between the plantar surface of the foot and the shoe. Although clinical awareness of the need to simultaneously measure shear and vertical forces under the foot has increased little has been done to provide the technology. This is mainly due to the difficulty in constructing devices capable of carrying out this task in the in-shoe environment. The aim of this paper is to describe the development and characteristics of a miniature triaxial transducer measuring 10 /spl times/ 10 /spl times/ 2.7 mm and a weight of only 2 g. This transducer is capable of simultaneously measuring three orthogonal forces under any location of the plantar surface of the foot utilizing a single element piezoelectric copolymer P(VDF-TrFE). Transducer sensitivity, linearity, hysteresis, crosstalk and temperature dependence is presented. As well as in-shoe force measurement, this triaxial transducer could have other biomedical and general engineering applications, e.g., prosthetic interface forces, handgrip forces, sport, robotics, etc.
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paper_title: A review of tactile sensing technologies with applications in biomedical engineering

paper_content:

Abstract Any device which senses information such as shape, texture, softness, temperature, vibration or shear and normal forces, by physical contact or touch, can be termed a tactile sensor. The importance of tactile sensor technology was recognized in the 1980s, along with a realization of the importance of computers and robotics. Despite this awareness, tactile sensors failed to be strongly adopted in industrial or consumer markets. In this paper, previous expectations of tactile sensors have been reviewed and the reasons for their failure to meet these expectations are discussed. The evolution of different tactile transduction principles, state of art designs and fabrication methods, and their pros and cons, are analyzed. From current development trends, new application areas for tactile sensors have been proposed. Literature from the last few decades has been revisited, and areas which are not appropriate for the use of tactile sensors have been identified. Similarly, the challenges that this technology needs to overcome in order to find its place in the market have been highlighted.
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paper_title: Validation of the Pliance X System in measuring interface pressure generated by pressure garment.

paper_content:

INTRODUCTION ::: Pressure monitoring is crucial for effective pressure therapy. Precise and reliable interface pressure measurement system, however, remains unavailable in current practice. ::: ::: ::: METHODOLOGY ::: This is a validation study on the application of a recently developed device, the Pliance X System, for static interface pressure measurement. Sensor properties were evaluated through series of laboratory tests in the first phase of the study. Phase II was a clinical study using the Pliance X system to differentiate the loading generated on the patients' scars through additional inserts and pressure garment. ::: ::: ::: RESULTS ::: Results showed high test-retest and inter-rater reliability (ICC > or = 0.995) with good linearity (adjusted R-square=0.997) by measuring standard weights. The maximum deviation between the measurement generated by the sensor and the sphygmomanometer cuff was +/-1.451 mmHg. Results in the clinical trial revealed its discriminant ability in distinguishing different levels of pressure loading on patients with scars (p<0.01). ::: ::: ::: CONCLUSION ::: The commercially available pressure measurement system was found to be a reliable tool for measurement of low interface pressure under static condition.
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paper_title: Development and validation of a 3D-printed interfacial stress sensor for prosthetic applications.

paper_content:

a b s t r a c t A novel capacitance-based sensor designed for monitoring mechanical stresses at the stump-socket inter- face of lower-limb amputees is described. It provides practical means of measuring pressure and shear stresses simultaneously. In particular, it comprises of a flexible frame (20 mm × 20 mm), with thickness of 4 mm. By employing rapid prototyping technology in its fabrication, it offers a low-cost and versatile solution, with capability of adopting bespoke shapes of lower-limb residua. The sensor was first ana- lysed using finite element analysis (FEA) and then evaluated using lab-based electromechanical tests. The results validate that the sensor is capable of monitoring both pressure and shear at stresses up to 350 kPa and 80 kPa, respectively. A post-signal processing model is developed to induce pressure and shear stresses, respectively. The effective separation of pressure and shear signals can be potentially advantageous for sensor calibration in clinical applications. The sensor also demonstrates high linearity (approx. 5-8%) and high pressure (approx. 1.3 kPa) and shear (approx. 0.6 kPa) stress resolution perfor- mance. Accordingly, the sensor offers the potential for exploitation as an assistive tool to both evaluate prosthetic socket fitting in clinical settings and alert amputees in home settings of excessive loading at the stump-socket interface, effectively preventing stump tissue breakdown at an early stage.
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paper_title: Pressure characteristics at the stump/socket interface in transtibial amputees using an adaptive prosthetic foot.

paper_content:

BACKGROUND ::: The technological advances that have been made in developing highly functional prostheses are promising for very active patients but we do not yet know whether they cause an increase in biomechanical load along with possibly negative consequences for pressure conditions in the socket. Therefore, this study monitored the socket pressure at specific locations of the stump when using a microprocessor-controlled adaptive prosthetic ankle under different walking conditions. ::: ::: ::: METHODS ::: Twelve unilateral transtibial amputees between 43 and 59 years of age were provided with the Proprio-Foot (Ossur) and underwent an instrumented 3D gait analysis in level, stair, and incline walking, including synchronous data capturing of socket pressure. Peak pressures and pressure time integrals (PTI) at three different locations were compared for five walking conditions with and without using the device's ankle adaptation mode. ::: ::: ::: FINDINGS ::: Highest peak pressures of 2.4 k Pa/kg were found for incline ascent at the calf muscle as compared to 2.1 k Pa/kg in level walking with large inter-individual variance. In stair ascent a strong correlation was found between maximum knee moment and socket pressure. The most significant pressure changes relative to level walking were seen in ramp descent anteriorly towards the stump end, with PTI values being almost twice as high as those in level walking. Adapting the angle of the prosthesis on stairs and ramps modified the pressure data such that they were closer to those in level walking. ::: ::: ::: INTERPRETATION ::: Pressure at the stump depends on the knee moments involved in each walking condition. Adapting the prosthetic ankle angle is a valuable means of modifying joint kinetics and thereby the pressure distribution at the stump. However, large inter-individual differences in local pressures underline the importance of individual socket fitting.
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paper_title: An interfacial stress sensor for biomechanical applications

paper_content:

This paper presents a capacitive sensor that measures interfacial forces in prostheses and is promising for other biomedical applications. These sensors can be integrated into prosthetic devices to measure both normal and shear stress simultaneously, allowing for the study of prosthetic limb fit, and ultimately for the ability to better adapt prosthetics to individual users. A sensing cell with a 1.0 cm2 spatial resolution and a measurement range of 0–220 kPa of shear and 0–2 MPa of pressure was constructed. The cell was load tested and found to be capable of isolating the applied shear and pressure forces. This paper discusses the construction of the prototype, the mechanical and electrode design, fabrication and characterization. The work presented is aimed at creating a class of adaptive prosthetic interfaces using a capacitive sensor.
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paper_title: A novel capacitive pressure sensor based on sandwich structures

paper_content:

This paper presents a sandwich structure for a capacitive pressure sensor. The sensor was fabricated by a simple three-mask process and sealed in vacuum by anodic bonding. The sensor, which utilizes a combined SiO/sub 2//Si/sub 3/N/sub 4/ layers as the elastic dielectric layers, exhibits high sensitivity. Mechanical characteristics of the sensor are theoretically analyzed based on a composite membrane theory and evaluated by use of finite element analysis (FEA). Square membrane sensors with side lengths of 800 /spl mu/m, 1000 /spl mu/m, 1200 /spl mu/m, and 1500 /spl mu/m were fabricated, providing a measured sensitivity of 0.08 pF/kPa, 0.12 pF/kPa, 0.15 pF/kPa, and 0.2 pF/kPa, respectively. The nonlinearity of the sensor is less than 1.2% over a dynamic range 80-106 kPa and the maximum hysteresis is about 3.3% to the full scale capacitance change. The TCO at 101 kPa is 1923 ppm//spl deg/C. All the electrodes of the sensor are leaded from the top side of the chip. Residual pressure in the sealed cavity at room temperature is evaluated by a pressure scanning test, indicating about 8 kPa. Comparison of experimental results with theoretical analysis shows that change of capacitance for the sandwich structure under pressure is mainly due to variation of the dielectric constant while geometric variations such as the area change of electrodes and the thickness change of dielectric layers is about two orders less than the variation of the dielectric constant. Sensitivity enhancements for the sensor are qualitatively discussed based on the physical effects of strained dielectrics, including electrostriction and flexoelectricity. [1551].
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paper_title: Laboratory and clinical tests of a prototype pressure sensor for clinical assessment of prosthetic socket fit

paper_content:

Lower limb prosthetic socket fabrication is a highly refined process relying on the prosthetist's skill and experience. Despite their best efforts, patients often return with complications. Additionally, clinical application of technological advances for the quantification of biomechanical factors at the socket interface has not changed in practice. Measuring pressure levels at the stump/socket interface could provide valuable information in the process of prosthetic socket fabrication, fit and modification. This paper presents findings on the performance of a prototype capacitance pressure sensor designed for prosthetic socket use. Bench tests using compressed air were performed to measure accuracy, hysteresis and drift responses in both a flatbed chamber and a custommodified pressure vessel. For the contoured testing, the sensors were placed on nine sites on a positive trans-tibial stump mould and enveloped with a silicone liner. Additionally, a preliminary clinical evaluation was performed with two trans-tibial amputee subjects at the nine sites during normal ambulation. Bench test results showed that the prototype capacitance sensor performed well in all categories, exhibiting a 2.42% (flatbed) and 9.96% (contoured) accuracy error, a 12.93% (flatbed) and 12.95% (contoured) hysteresis error, and a 4.40% (flatbed) and 6.20% All correspondence to be addressed to Dr. Adrian A. Polliack, Senior Vice-President for Research,
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paper_title: Characterization of a capacitive tactile shear sensor for application in robotic and upper limb prostheses

paper_content:

Abstract This paper presents the characterization of a novel tactile sensor designed to measure shear forces. The sensor design is targeted for use in robotic and prosthetic hands, where haptic feedback or ability to detect shear forces associated with slip are critical. The presented sensor utilizes the principle of differential capacitance to measure the mechanical deflection of the sensor element. The dynamic range of the sensor can be varied by encapsulating the sensor terminal within silicone of varying hardness. The design features ease of mass production, low per-unit-cost, novel overload protection and low wire count, while still preserving the ability to achieve reasonable spatial resolutions and array densities. Mathematical and COMSOL multiphysics models of the sensor are presented, in addition to results from practical experiments. Sensors with a full scale displacement range of ±0.525 mm were produced and the differential capacitance was measured. Shear force transduction was characterized over the range of 0 N–4 N with the sense terminal encapsulated by silicone with a shore A hardness of 20. The effect of elastomer hardness on the sensor's dynamic range was analyzed. The differential capacitance, when measured at each fixed interval, was found experimentally to have a maximum standard deviation of 4.28e−16 F over a ±2 N range. A maximum standard deviation of 1.35e−15 F was measured across characterized full scale sensor range of ±4 N. The sensor design has a sensitivity of 1.967 fF/N of applied force and the sensor output was found to be approximately linear. The coefficient of determination, r 2 , was found to be 0.941.
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paper_title: Review of interface pressure measurement to establish a protocol for their use in the assessment of patient support surfaces.

paper_content:

The interface pressure (IP) between a body and support surface is one objective measure used in the evaluation of the wide variety of pressure relieving equipment that exists for the prevention and treatment of pressure sores. We present a review of the literature associated with making these measurements and discuss the acute need to be able to use them to choose the most effective 'anti-pressure sore devices' for patient care, as well as discussing the difficulties associated with this decision making. We focus on interface pressure monitors describing their development and discussing the questions that remain about the accuracy and relevance of their measurements. An outline of the strengths and limitations of the most commonly used pressure sensors is given. There remains a gap in research in this area that is clinically specific and the need to be able to assess these anti-pressure sore devices with patients in a hospital environment is highlighted. The variants involved in assessing patients on various mattresses and the difficulties associated with this are described. A protocol is suggested in an attempt to improve the use of such devices and establish a better method for quantifying the clinical effectiveness of different support surfaces.
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paper_title: Triaxial force transducer for investigating stresses at the stump/socket interface

paper_content:

Although normal pressures at the stump socket interface of the lower-limb amputee have been investigated, little is known about the shear stresses that also occur. Studies suggest that the combination of both shear and normal stresses significantly exacerbates discomfort and vascular and tissue damage. A means of simultaneously measuring normal and shear stresses will aid in the investigation and improvement of prosthetic fit. A miniature triaxial force transducer (4.9 x 16 mm diameter) has been developed which can be recessed into the socket wall. The principle of operation, construction, performance and limitations of the device are described. Preliminary measurements of the interface stress variations over the gait cycle in a supra-condylar PTB socket are presented. These show clear differences in the stress patterns present when two different prosthetic feet are used.
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paper_title: Intensity‐modulated fiber optic sensor for health monitoring applications: a comparative review

paper_content:

Purpose – The purpose of this paper is to provide a comparative review of intensity‐modulated fiber optic sensors with non‐optical sensors for health monitoring applications, from the current research activities in the area.Design/methodology/approach – A range of published research work in sensor design for four different health monitoring applications, including, lumbar spine bending, upper and lower limb motion tracking, respiration and heart rate monitoring, are presented and discussed in terms of their respective advantages and limitations.Findings – This paper provides information on the various types of sensors applied into the health monitoring area. The sensing techniques of the fiber optic sensor for the stated applications are focused and compared in details to highlight their contributions.Originality/value – A comparative review of published work is illustrated in an informative table content, to allow a clear idea of the current sensing approaches for health monitoring applications.
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paper_title: Body‐Monitoring and Health Supervision by Means of Optical Fiber‐Based Sensing Systems in Medical Textiles

paper_content:

Long-term monitoring with optical fibers has moved into the focus of attention due to the applicability for medical measurements. Within this Review, setups of flexible, unobtrusive body-monitoring systems based on optical fibers and the respective measured vital parameters are in focus. Optical principles are discussed as well as the interaction of light with tissue. Optical fiber-based sensors that are already used in first trials are primarily selected for the section on possible applications. These medical textiles include the supervision of respiration, cardiac output, blood pressure, blood flow and its saturation with hemoglobin as well as oxygen, pressure, shear stress, mobility, gait, temperature, and electrolyte balance. The implementation of these sensor concepts prompts the development of wearable smart textiles. Thus, current sensing techniques and possibilities within photonic textiles are reviewed leading to multiparameter designs. Evaluation of these designs should show the great potential of optical fibers for the introduction into textiles especially due to the benefit of immunity to electromagnetic radiation. Still, further improvement of the signal-to-noise ratio is often necessary to develop a commercial monitoring system.
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paper_title: Fibre Optic Sensors for Structural Health Monitoring of Aircraft Composite Structures: Recent Advances and Applications

paper_content:

In-service structural health monitoring of composite aircraft structures plays a key role in the assessment of their performance and integrity. In recent years, Fibre Optic Sensors (FOS) have proved to be a potentially excellent technique for real-time in-situ monitoring of these structures due to their numerous advantages, such as immunity to electromagnetic interference, small size, light weight, durability, and high bandwidth, which allows a great number of sensors to operate in the same system, and the possibility to be integrated within the material. However, more effort is still needed to bring the technology to a fully mature readiness level. In this paper, recent research and applications in structural health monitoring of composite aircraft structures using FOS have been critically reviewed, considering both the multi-point and distributed sensing techniques.
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paper_title: From conventional sensors to fibre optic sensors for strain and force measurements in biomechanics applications: A review

paper_content:

Abstract In vivo measurement, not only in animals but also in humans, is a demanding task and is the ultimate goal in experimental biomechanics. For that purpose, measurements in vivo must be performed, under physiological conditions, to obtain a database and contribute for the development of analytical models, used to describe human biomechanics. The knowledge and control of the mechanisms involved in biomechanics will allow the optimization of the performance in different topics like in clinical procedures and rehabilitation, medical devices and sports, among others. Strain gages were first applied to bone in a live animal in 40׳s and in 80׳s for the first time were applied fibre optic sensors to perform in vivo measurements of Achilles tendon forces in man. Fibre optic sensors proven to have advantages compare to conventional sensors and a great potential for biomechanical and biomedical applications. Compared to them, they are smaller, easier to implement, minimally invasive, with lower risk of infection, highly accurate, well correlated, inexpensive and multiplexable. The aim of this review article is to give an overview about the evolution of the experimental techniques applied in biomechanics, from conventional to fibre optic sensors. In the next sections the most relevant contributions of these sensors, for strain and force in biomechanical applications, will be presented. Emphasis was given to report of in vivo experiments and clinical applications.
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paper_title: Fibre optic Bragg grating sensors : An alternative method to strain gauges for measuring deformation in bone

paper_content:

Abstract Strain gauges are currently the default method for measuring deformation in bone. Strain gauges are not well suited for in vivo measurements because of their size and because they are difficult to use in bone. They are also unsuitable for repeated measurements over time since they cannot be left in the patient. The optical Bragg grating fibres behave like selective filters of light. As a result the structure will transmit most wavelengths of light, but will reflect certain specific wavelengths. If the Bragg grating is strained along the fibre axis, the wavelength will shift, and this change represents a measure of strain. The optical fibres are very thin, no thicker than a standard surgical suture and are easy to adhere to bone by use of the FDA approved polymethyl-methacrylate (PMMA) as bonding adhesive. Since they are made of biocompatible silica porous bioglass ceramics, it should also be possible to leave the fibres in the patient between and after measurements. We have shown that fibre optic Bragg grating sensors can be used as a measurement tool for bone strain by performing measurements both on an acryl tube and on an extracted sample of human femur diaphysis. On either of them we used four fibre optic sensors and four strain gauges, interspersed at every 45° around the circumference. The standard deviation of the measurements on the acrylic tube for each of the sensors, both optical fibres and strain gauges, varied from 1.0 to 5.2%. Every sensor, both optical fibre and strain gauge, correlated significantly with all of the rest at the 0.01 level with a Pearson correlation coefficient r ranging from 0.986 to 1.0. The linearity for all of the sensors versus load was excellent, the lowest linearity of the eight sensors was 0.996 as expressed by r 2 (coefficient of determination), with no significant difference in linearity between optical fibres and strain gauges. Bone is not an ideal isotropic material, and we found that the strain readings of the sensors in the bone study showed less linearity than in the acryl tube study. The correlations between all sensors, both optical fibres and strain gauges, were less strong in the bone sample than acrylic tube with a Pearson correlation coefficient on the bone sample ranging from 0.629 to 0.999 and with a standard deviation of the measurements varying from 3.1 to 31.5%. However, no significant differences between strain gauges and optic fibres were found, neither in the acrylic tube measurements nor the bone sample measurements. Optical Bragg grating fibres are therefore well suited for dynamic measurements of strain in bone in vitro and should also be suitable for use on bone in vivo .
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paper_title: Fiber Bragg Grating Sensors for Harsh Environments

paper_content:

Because of their small size, passive nature, immunity to electromagnetic interference, and capability to directly measure physical parameters such as temperature and strain, fiber Bragg grating sensors have developed beyond a laboratory curiosity and are becoming a mainstream sensing technology. Recently, high temperature stable gratings based on regeneration techniques and femtosecond infrared laser processing have shown promise for use in extreme environments such as high temperature, pressure or ionizing radiation. Such gratings are ideally suited for energy production applications where there is a requirement for advanced energy system instrumentation and controls that are operable in harsh environments. This paper will present a review of some of the more recent developments.
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paper_title: Two dimensional polymer-embedded quasi-distributed FBG pressure sensor for biomedical applications

paper_content:

We report on the development of a flexible 2D optical fiber-based pressure sensing surface suitable for biomedical applications. The sensor comprises of highly-sensitive Fiber Bragg Grating elements embedded in a thin polymer sheet to form a 2x2 cm(2) sensing pad with a minimal thickness of 2.5mm, while it is easily expandable in order to be used as a building block for larger surface sensors. The fabricated pad sensor was combined with a low physical dimension commercially available interrogation unit to enhance the portability features of the complete sensing system. Sensor mechanical properties allow for matching human skin behavior, while its operational performance exhibited a maximum fractional pressure sensitivity of 12 MPa(-1) with a spatial resolution of 1x1cm(2) and demonstrated no hysteresis and real time operation. These attractive operational and mechanical properties meet the requirements of various biomedical applications with respect to human skin pressure measurements, including amputee sockets, shoe sensors, wearable sensors, wheelchair seating-system sensors, hospital-bed monitoring sensors.
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paper_title: Sensing Pressure Distribution on a Lower-Limb Exoskeleton Physical Human-Machine Interface

paper_content:

A sensory apparatus to monitor pressure distribution on the physical human-robot interface of lower-limb exoskeletons is presented. We propose a distributed measure of the interaction pressure over the whole contact area between the user and the machine as an alternative measurement method of human-robot interaction. To obtain this measure, an array of newly-developed soft silicone pressure sensors is inserted between the limb and the mechanical interface that connects the robot to the user, in direct contact with the wearer's skin. Compared to state-of-the-art measures, the advantage of this approach is that it allows for a distributed measure of the interaction pressure, which could be useful for the assessment of safety and comfort of human-robot interaction. This paper presents the new sensor and its characterization, and the development of an interaction measurement apparatus, which is applied to a lower-limb rehabilitation robot. The system is calibrated, and an example its use during a prototypical gait training task is presented.
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paper_title: Fiber Optic-Based Pressure Sensing Surface for Skin Health Management in Prosthetic and Rehabilitation Interventions

paper_content:

© 2012 Kanellos et al., licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Fiber Optic–Based Pressure Sensing Surface for Skin Health Management in Prosthetic and Rehabilitation Interventions
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paper_title: Review of fiber-optic pressure sensors for biomedical and biomechanical applications

paper_content:

Abstract. As optical fibers revolutionize the way data is carried in telecommunications, the same is happening in the world of sensing. Fiber-optic sensors (FOS) rely on the principle of changing the properties of light that propagate in the fiber due to the effect of a specific physical or chemical parameter. We demonstrate the potentialities of this sensing concept to assess pressure in biomedical and biomechanical applications. FOSs are introduced after an overview of conventional sensors that are being used in the field. Pointing out their limitations, particularly as minimally invasive sensors, is also the starting point to argue FOSs are an alternative or a substitution technology. Even so, this technology will be more or less effective depending on the efforts to present more affordable turnkey solutions and peer-reviewed papers reporting in vivo experiments and clinical trials.
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paper_title: Recent Improvement of Medical Optical Fibre Pressure and Temperature Sensors

paper_content:

This investigation describes a detailed analysis of the fabrication and testing of optical fibre pressure and temperature sensors (OFPTS). The optical sensor of this research is based on an extrinsic Fabry–Perot interferometer (EFPI) with integrated fibre Bragg grating (FBG) for simultaneous pressure and temperature measurements. The sensor is fabricated exclusively in glass and with a small diameter of 0.2 mm, making it suitable for volume-restricted bio-medical applications. Diaphragm shrinking techniques based on polishing, hydrofluoric (HF) acid and femtosecond (FS) laser micro-machining are described and analysed. The presented sensors were examined carefully and demonstrated a pressure sensitivity in the range of sp = 2–10 nmkPa and a resolution of better than ΔP = 10 Pa (0.1 cm H2O). A static pressure test in 38 cmH2O shows no drift of the sensor in a six-day period. Additionally, a dynamic pressure analysis demonstrated that the OFPTS never exceeded a drift of more than 130 Pa (1.3 cm H2O) in a 12-h measurement, carried out in a cardiovascular simulator. The temperature sensitivity is given by k=10.7 pmK, which results in a temperature resolution of better than ΔT = 0.1 K. Since the temperature sensing element is placed close to the pressure sensing element, the pressure sensor is insensitive to temperature changes.
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paper_title: Optical Fibre Pressure Sensors in Medical Applications

paper_content:

This article is focused on reviewing the current state-of-the-art of optical fibre pressure sensors for medical applications. Optical fibres have inherent advantages due to their small size, immunity to electromagnetic interferences and their suitability for remote monitoring and multiplexing. The small dimensions of optical fibre-based pressure sensors, together with being lightweight and flexible, mean that they are minimally invasive for many medical applications and, thus, particularly suited to in vivo measurement. This means that the sensor can be placed directly inside a patient, e.g., for urodynamic and cardiovascular assessment. This paper presents an overview of the recent developments in optical fibre-based pressure measurements with particular reference to these application areas.
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paper_title: The Use of Fiberoptics in Clinical Cardiac Catheterization II. In Vivo Dye-Dilution Curves

paper_content:

Intracardiac blood oxygen saturation was determined in 31 patients, at cardiac catheterization, by means of a fiberoptic in vivo hemoreflection system, giving an immediate report. When compared to in vitro spectrophotometric analysis of samples obtained through a second catheter, a standard error of estimate of only 1.99-per cent saturation (r = 0.966) was found for the higher speed instrument (response time 0.07 second) and 1.13-per cent saturation (r = 0.992) for the slower instrument (response time 1.5 seconds). The average of the standard deviations of saturation values in cardiac chambers in which no primary mixing occurred, was only 0.88-per cent saturation. The continuous recording of oxygen saturation while moving the catheter, permits measurements at multiple sites within a brief period of time (14 to 26 seconds through the right side of the heart). Oxygen saturation changes can be continuously monitored under changing conditions, such as exercise. Finally, the higher speed instrument permits inv...
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paper_title: Filmed extrinsic Fabry–Perot interferometric sensors for the measurement of arbitrary refractive index of liquid

paper_content:

Abstract A filmed extrinsic Fabry–Perot interferometric (FEFPI) sensor for the measurement of arbitrary refractive index (RI) is experimentally demonstrated. The FEFPI sensor was constructed by aligning two fiber endfaces, on which the multilayer dielectric mirrors are deposited. There is a fixed reflection at the filmed fiber endface no matter how much the RI is, and we can obtain a clear interferogram with a high visibility. A resolution of up to 1.64 × 10 −5 refractive index unit is achieved in our experiment.
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paper_title: Advances in Bio-Tactile Sensors for Minimally Invasive Surgery Using the Fibre Bragg Grating Force Sensor Technique:A Survey

paper_content:

The large interest in utilising fibre Bragg grating (FBG) strain sensors for minimally invasive surgery (MIS) applications to replace conventional electrical tactile sensors has grown in the past few years. FBG strain sensors offer the advantages of optical fibre sensors, such as high sensitivity, immunity to electromagnetic noise, electrical passivity and chemical inertness, but are not limited by phase discontinuity or intensity fluctuations. FBG sensors feature a wavelength-encoding sensing signal that enables distributed sensing that utilises fewer connections. In addition, their flexibility and lightness allow easy insertion into needles and catheters, thus enabling localised measurements inside tissues and blood. Two types of FBG tactile sensors have been emphasised in the literature: single-point and array FBG tactile sensors. This paper describes the current design, development and research of the optical fibre tactile techniques that are based on FBGs to enhance the performance of MIS procedures in general. Providing MIS or microsurgery surgeons with accurate and precise measurements and control of the contact forces during tissues manipulation will benefit both surgeons and patients.
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paper_title: Optical Bragg grating sensor fibers for ultra-high temperature applications

paper_content:

Sapphire based optical fibers provide an attractive basis for ultra-high temperature stable optical sensor elements. Fiber Bragg gratings can be inscribed in such fibers by means of femtosecond-laser pulses with a wavelength of 400 nm in combination with a two-beam phase mask interferometer. We have investigated crystalline optical fibers as well as structured sapphire-derived all glass optical fibers with aluminum content in the core of up to 50 mol%. The reflection properties, the index modulation and the attenuation effects will be discussed. Results concerning the temperature and strain sensitivity for use as sensor elements at high temperatures will be presented.
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paper_title: Fiber grating sensors in medicine: Current and emerging applications

paper_content:

Fiber grating sensors hold immense potential for biomedical applications due to their inherent properties like small size, biocompatibility, non-toxicity, chemical inertness and electromagnetically inert nature. Grating based sensors are well known technology for structural health monitoring (SHM) in the arena of civil and aerospace; however investigations for their use in the field of medicine are fairly recent and they have not been yet commercialized for the same. As these sensors detect strain, temperature, pressure, vibration, curvature and refractive index of the surrounding material even in high magnetic and electric field environments, they can serve diagnostic purposes in diverse areas of healthcare e.g. biomechanics, cardiology, gynecology, very low temperature monitoring and immunosensing to name a few. Most importantly, they can be used efficiently for thermal and pressure mapping even during MRI procedure where conventional sensors may fail. The paper is a review of various application areas of fiber grating based devices, the status of precedent and ongoing research around the world, and discussion on the issues hampering their rapid growth in the field.
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paper_title: Pressure sensor based on the fiber-optic extrinsic Fabry-Perot interferometer

paper_content:

Pressure sensors based on fiber-optic extrinsic Fabry-Perot interferometer (EFPI) have been extensively applied in various industrial and biomedical fields. In this paper, some key improvements of EFPI-based pressure sensors such as the controlled thermal bonding technique, diaphragm-based EFPI sensors, and white light interference technology have been reviewed. Recent progress on signal demodulation method and applications of EFPI-based pressure sensors has been introduced. Signal demodulation algorithms based on the cross correlation and mean square error (MSE) estimation have been proposed for retrieving the cavity length of EFPI. Absolute measurement with a resolution of 0.08 nm over large dynamic range has been carried out. For downhole monitoring, an EFPI and a fiber Bragg grating (FBG) cascade multiplexing fiber-optic sensor system has been developed, which can operate in temperature 300 °C with a good long-term stability and extremely low temperature cross-sensitivity. Diaphragm-based EFPI pressure sensors have been successfully used for low pressure and acoustic wave detection. Experimental results show that a sensitivity of 31 mV/Pa in the frequency range of 100 Hz to 12.7 kHz for aeroacoustic wave detection has been obtained.
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paper_title: Development of an in-shoe pressure-sensitive device for gait analysis

paper_content:

In this work, we present the development of an in-shoe device to monitor plantar pressure distribution for gait analysis. The device consists in a matrix of 64 sensitive elements, integrated with in-shoe electronics and battery which provide an high-frequency data acquisition, wireless transmission and an average autonomy of 7 hours in continuous working mode. The device is presented along with its experimental characterization and a preliminary validation on a healthy subject.
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paper_title: Miniature fiber-optic force sensor based on low-coherence Fabry-Pérot interferometry for vitreoretinal microsurgery

paper_content:

During vitreoretinal surgery, the surgeon manipulates retinal tissue with tool-to-tissue interaction forces below the human sensory threshold. A force sensor (FS) integrated with conventional surgical tools may significantly improve the surgery outcome by providing tactile feedback to the surgeon. We designed and built a surgical tool integrated with a miniature FS with an outer diameter smaller than 1 mm for vitreoretinal surgery based on low-coherence Fabry–Perot (FP) interferometry. The force sensing elements are located at the tool tip which is in direct contact with tissue during surgery and the FP cavity length is interrogated by a fiber-optic common-path phase-sensitive optical coherence tomography (OCT) system. We have calibrated the FS's response to axial and lateral forces and conducted experiments to verify that our FS can simultaneously measure both axial and lateral force components.
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paper_title: Review of diverse optical fibers used in biomedical research and clinical practice

paper_content:

Optical fiber technology has significantly bolstered the growth of photonics applications in basic life sciences research and in biomedical diagnosis, therapy, monitoring, and surgery. The unique operational characteristics of diverse fibers have been exploited to realize advanced biomedical functions in areas such as illumination, imaging, minimally invasive surgery, tissue ablation, biological sensing, and tissue diagnosis. This review paper provides the necessary background to understand how optical fibers function, to describe the various categories of available fibers, and to illustrate how specific fibers are used for selected biomedical photonics applications. Research articles and vendor data sheets were consulted to describe the operational characteristics of conventional and specialty multimode and single-mode solid-core fibers, double-clad fibers, hard-clad silica fibers, conventional hollow-core fibers, photonic crystal fibers, polymer optical fibers, side-emitting and side-firing fibers, middle-infrared fibers, and optical fiber bundles. Representative applications from the recent literature illustrate how various fibers can be utilized in a wide range of biomedical disciplines. In addition to helping researchers refine current experimental setups, the material in this review paper will help conceptualize and develop emerging optical fiber-based diagnostic and analysis tools.
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paper_title: Low-cost/high-reproducibility flexible sensor based on photonics for strain measuring

paper_content:

This paper presents a flexible sensor based on photonics for measuring strain, curvatures and vibrations. This flexible sensor is composed by a Fiber Bragg Grating (FBG) embedded into polydimethylsiloxane (PDMS). The selected FBG resonates at the wavelength of 1552.37 nm and is embedded before the curing for enabling a strong adhesion between both components. Few prototypes were fabricated and characterized. The measurements showed a maximum strain sensitivity of E400 pm per 1% elongation, revealing to be sensitive to strain/bending forces and vibration. The measurements allowed to establish a predictable response for both static and dynamic behavior, corresponding to a resolution of E88 pm per curvature degree. This flexible sensor also allowed high strain cycles and presented the linear behavior of E14 pm 1C -1 over the temperature range 20-110 1C. The high-simplicity of the fabrication process results on low-cost with high-degree of reproducibility of their characteristics.
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paper_title: Soft Fiber Optic Sensors for Precision Measurement of Shear Stress and Pressure

paper_content:

This paper reports a soft fiber optic sensor based on polymer fiber Bragg gratings (PFBGs) for simultaneous measurement of shear and normal stresses. The sensor comprises two PFBGs embedded in soft polydimethylsiloxanes (PDMS) matrix, and one of them is horizontally placed while the other is tilted. The transduction principle is that applied normal and/or shear stresses lead to deformation of the matrix and induce strains on gratings. Finite element simulation reveals non-uniform strain distribution along two fibers for direct imbedding that is verified by theoretical analysis, and therefore four gaskets are used to stretch polymer optical fibers from two ends and to produce strains on gratings. The fabricated sensor is tested by concurrently applying normal and shear forces, and Bragg wavelength shifts of two gratings were found to be linearly dependent on stresses in two directions. The measured pressure sensitivity is 0.8 pm/Pa in the range of 2.4 kPa and the shear stress sensitivity is 1.3 pm/Pa for a full range of 0.6 kPa. Such soft sensors are especially suitable for high precision measurement of contact stresses involving human skins and tissues because they are similar in Young's modulus to the used PDMS.
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paper_title: The Use of Fiber Bragg Grating Sensors in Biomechanics and Rehabilitation Applications: The State-of-the-Art and Ongoing Research Topics

paper_content:

In recent years, fiber Bragg gratings (FBGs) are becoming increasingly attractive for sensing applications in biomechanics and rehabilitation engineering due to their advantageous properties like small size, light weight, biocompatibility, chemical inertness, multiplexing capability and immunity to electromagnetic interference (EMI). They also offer a high-performance alternative to conventional technologies, either for measuring a variety of physical parameters or for performing high-sensitivity biochemical analysis. FBG-based sensors demonstrated their feasibility for specific sensing applications in aeronautic, automotive, civil engineering structure monitoring and undersea oil exploration; however, their use in the field of biomechanics and rehabilitation applications is very recent and its practicality for full-scale implementation has not yet been fully established. They could be used for detecting strain in bones, pressure mapping in orthopaedic joints, stresses in intervertebral discs, chest wall deformation, pressure distribution in Human Machine Interfaces (HMIs), forces induced by tendons and ligaments, angles between body segments during gait, and many others in dental biomechanics. This article aims to provide a comprehensive overview of all the possible applications of FBG sensing technology in biomechanics and rehabilitation and the status of ongoing researches up-to-date all over the world, demonstrating the FBG advances over other existing technologies.
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paper_title: A Flexible Sensor Technology for the Distributed Measurement of Interaction Pressure

paper_content:

We present a sensor technology for the measure of the physical human-robot interaction pressure developed in the last years at Scuola Superiore Sant'Anna. The system is composed of flexible matrices of opto-electronic sensors covered by a soft silicone cover. This sensory system is completely modular and scalable, allowing one to cover areas of any sizes and shapes, and to measure different pressure ranges. In this work we present the main application areas for this technology. A first generation of the system was used to monitor human-robot interaction in upper- (NEUROExos; Scuola Superiore Sant'Anna) and lower-limb (LOPES; University of Twente) exoskeletons for rehabilitation. A second generation, with increased resolution and wireless connection, was used to develop a pressure-sensitive foot insole and an improved human-robot interaction measurement systems. The experimental characterization of the latter system along with its validation on three healthy subjects is presented here for the first time. A perspective on future uses and development of the technology is finally drafted.
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paper_title: Enhanced durability FBG-based sensor pads for biomedical applications as human-machine interface surfaces

paper_content:

We present pressure FBG-based sensor pads that exhibit enhanced durability and are suitable for application in human-machine interface surfaces for rehabilitation and biomechanics applications, such as medical beds, wheelchairs and amputee sockets.
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paper_title: MRI-Compatible Fiber-Optic Force Sensors for Catheterization Procedures

paper_content:

Cardiac catheterization is an interventional procedure that is usually carried out without the use of force sensors. During such procedures the physician mainly relies on visual feedback provided by an imaging modality, like X-ray fluoroscopy, Computed Tomography (CT) or Magnetic Resonance Imaging (MRI). Hence, the physician it is not always able to predict the forces between the catheter and blood vessel walls. Sometimes, tasks such as moving a catheter through delicate blood vessel networks and through the heart chambers become difficult. This paper provides an overview of fiber-optic pressure and force sensors for cardiac catheters with potential for providing haptic feedback. In conjunction with an MRI scanner the overall cardiac catheterization procedure could be enhanced. The paper focuses on fiber-optic sensors due to their very good MRI compatibility. Background information on manual and robotic catheterization approaches is provided together with an analytic discussion of the current state-of-the-art in fiber-optic force and pressure sensors for catheters, which can provide haptic information.
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paper_title: Cure monitoring of smart composites using Fiber Bragg Grating based embedded sensors

paper_content:

A sensor embedded in the composite laminate can act as a temperature transducer during the composite cure mechanism. Once the composite is cured, the same sensor can be used to provide the information about the mechanical changes that influence the performance of the material. Fiber Bragg Grating (FBG) sensor is one such sensor which one can use for the composite cure monitoring. We present here the results obtained with an associated FBG sensor system for the cure monitoring of smart composites. The performance of the embedded FBG sensor smart composite specimens under 3- and 4-point bending conditions are also being investigated. Finally, the performance analysis has been extended to cantilever specimens.
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paper_title: Fibre Optic Sensors for Structural Health Monitoring of Aircraft Composite Structures: Recent Advances and Applications

paper_content:

In-service structural health monitoring of composite aircraft structures plays a key role in the assessment of their performance and integrity. In recent years, Fibre Optic Sensors (FOS) have proved to be a potentially excellent technique for real-time in-situ monitoring of these structures due to their numerous advantages, such as immunity to electromagnetic interference, small size, light weight, durability, and high bandwidth, which allows a great number of sensors to operate in the same system, and the possibility to be integrated within the material. However, more effort is still needed to bring the technology to a fully mature readiness level. In this paper, recent research and applications in structural health monitoring of composite aircraft structures using FOS have been critically reviewed, considering both the multi-point and distributed sensing techniques.
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paper_title: Tactile sensing for dexterous in-hand manipulation in robotics-A review

paper_content:

Abstract As the field of robotics is expanding from the fixed environment of a production line to complex human environments, robots are required to perform increasingly human-like manipulation tasks, moving the state-of-the-art in robotics from grasping to advanced in-hand manipulation tasks such as regrasping, rotation and translation. To achieve advanced in-hand manipulation tasks, robotic hands are required to be equipped with distributed tactile sensing that can continuously provide information about the magnitude and direction of forces at all contact points between them and the objects they are interacting with. This paper reviews the state-of-the-art in force and tactile sensing technologies that can be suitable within the specific context of dexterous in-hand manipulation. In previous reviews of tactile sensing for robotic manipulation, the specific functional and technical requirements of dexterous in-hand manipulation, as compared to grasping, are in general not taken into account. This paper provides a review of models describing human hand activity and movements, and a set of functional and technical specifications for in-hand manipulation is defined. The paper proceeds to review the current state-of-the-art tactile sensor solutions that fulfil or can fulfil these criteria. An analytical comparison of the reviewed solutions is presented, and the advantages and disadvantages of different sensing technologies are compared.
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paper_title: Embedded flexible optical shear sensor

paper_content:

Monitoring shear stresses is increasingly important in the medical sector, where the sensors need to be unobtrusive, compact and flexible. A very thin and flexible sensor foil is presented based on the shear stress dependent coupling change of optical power between a laser and photodiode chip that were separated by a deformable sensing layer. These opto-electronic components were embedded in a very thin foil of only 40µm thick. The sensitivity and measurement range can be modified by selecting the material properties of the sensing layer. The sensor response showed to be reproducible and the influence of normal pressure on the sensor was very limited.
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paper_title: An optical 3D force sensor for biomedical devices

paper_content:

In this paper we describe the development of an optical sensor that is low profile, inexpensive, physically robust, and suitable for contact with soft tissue. It is constructed using commercially available integrated circuits, a printed circuit board, and layers of silicone elastomer. The sensor exhibits modest drift and hysteresis, as well as some temperature sensitivity, for which we compensate. We demonstrate how the raw sensor signals can be used to infer both normal and shear forces. The sensor proves to be particularly sensitive to shear forces, reporting them accurately and with minimal coupling between them.
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paper_title: A Flexible Sensor Technology for the Distributed Measurement of Interaction Pressure

paper_content:

We present a sensor technology for the measure of the physical human-robot interaction pressure developed in the last years at Scuola Superiore Sant'Anna. The system is composed of flexible matrices of opto-electronic sensors covered by a soft silicone cover. This sensory system is completely modular and scalable, allowing one to cover areas of any sizes and shapes, and to measure different pressure ranges. In this work we present the main application areas for this technology. A first generation of the system was used to monitor human-robot interaction in upper- (NEUROExos; Scuola Superiore Sant'Anna) and lower-limb (LOPES; University of Twente) exoskeletons for rehabilitation. A second generation, with increased resolution and wireless connection, was used to develop a pressure-sensitive foot insole and an improved human-robot interaction measurement systems. The experimental characterization of the latter system along with its validation on three healthy subjects is presented here for the first time. A perspective on future uses and development of the technology is finally drafted.
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paper_title: Fibre Optic Sensors for Structural Health Monitoring of Aircraft Composite Structures: Recent Advances and Applications

paper_content:

In-service structural health monitoring of composite aircraft structures plays a key role in the assessment of their performance and integrity. In recent years, Fibre Optic Sensors (FOS) have proved to be a potentially excellent technique for real-time in-situ monitoring of these structures due to their numerous advantages, such as immunity to electromagnetic interference, small size, light weight, durability, and high bandwidth, which allows a great number of sensors to operate in the same system, and the possibility to be integrated within the material. However, more effort is still needed to bring the technology to a fully mature readiness level. In this paper, recent research and applications in structural health monitoring of composite aircraft structures using FOS have been critically reviewed, considering both the multi-point and distributed sensing techniques.
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paper_title: Tactile sensing for dexterous in-hand manipulation in robotics-A review

paper_content:

Abstract As the field of robotics is expanding from the fixed environment of a production line to complex human environments, robots are required to perform increasingly human-like manipulation tasks, moving the state-of-the-art in robotics from grasping to advanced in-hand manipulation tasks such as regrasping, rotation and translation. To achieve advanced in-hand manipulation tasks, robotic hands are required to be equipped with distributed tactile sensing that can continuously provide information about the magnitude and direction of forces at all contact points between them and the objects they are interacting with. This paper reviews the state-of-the-art in force and tactile sensing technologies that can be suitable within the specific context of dexterous in-hand manipulation. In previous reviews of tactile sensing for robotic manipulation, the specific functional and technical requirements of dexterous in-hand manipulation, as compared to grasping, are in general not taken into account. This paper provides a review of models describing human hand activity and movements, and a set of functional and technical specifications for in-hand manipulation is defined. The paper proceeds to review the current state-of-the-art tactile sensor solutions that fulfil or can fulfil these criteria. An analytical comparison of the reviewed solutions is presented, and the advantages and disadvantages of different sensing technologies are compared.
---
paper_title: Embedded flexible optical shear sensor

paper_content:

Monitoring shear stresses is increasingly important in the medical sector, where the sensors need to be unobtrusive, compact and flexible. A very thin and flexible sensor foil is presented based on the shear stress dependent coupling change of optical power between a laser and photodiode chip that were separated by a deformable sensing layer. These opto-electronic components were embedded in a very thin foil of only 40µm thick. The sensitivity and measurement range can be modified by selecting the material properties of the sensing layer. The sensor response showed to be reproducible and the influence of normal pressure on the sensor was very limited.
---
paper_title: An optical 3D force sensor for biomedical devices

paper_content:

In this paper we describe the development of an optical sensor that is low profile, inexpensive, physically robust, and suitable for contact with soft tissue. It is constructed using commercially available integrated circuits, a printed circuit board, and layers of silicone elastomer. The sensor exhibits modest drift and hysteresis, as well as some temperature sensitivity, for which we compensate. We demonstrate how the raw sensor signals can be used to infer both normal and shear forces. The sensor proves to be particularly sensitive to shear forces, reporting them accurately and with minimal coupling between them.
---
paper_title: Socket/stump interface dynamic pressure distributions recorded during the prosthetic stance phase of gait of a trans-tibial amputee wearing a hydrocast socket

paper_content:

Force sensing resistors (FSR) have been used to measure dynamic stump/socket interface pressures during the gait of a trans-tibial amputee. A total of 350 pressure sensors were attached to the inner wall of a hydrocast socket. Data were sampled at 150Hz during approximately 0.8 seconds of prosthetic stance of gait. The dynamic pressure distributions within a hand cast socket reported by Convery and Buis (1998) are compared with those monitored within a hydrocast socket for the same amputee. The pressure gradients within the hydrocast socket are less than that of the hand cast Patellar-Tendon-Bearing (PTB) socket. The proximal “ring” of high pressure in the hand cast PTB socket is replaced with a more distal pressure in the hydrocast socket.
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paper_title: Conventional patellar-tendon-bearing (PTB) socket/stump interface dynamic pressure distributions recorded during the prosthetic stance phase of gait of a transtibial amputee

paper_content:

Force sensing resistors (FSR) have been used to measure dynamic stump/socket interface pressures during the gait of a trans-tibial amputee. A total of 350 pressure sensor cells were attached to the inner wall of a patellar-tendon-bearing (PTB) socket. Data was sampled at 150 Hz during the approximate 0.8 seconds of prosthetic stance of gait. A total of 42,000 pressures were recorded during a single prosthetic stance. This paper describes the distribution of the pressure patterns monitored during the prosthetic stance phase of gait.
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paper_title: Pressure distribution at the stump/socket interface in transtibial amputees during walking on stairs, slope and non-flat road.

paper_content:

BACKGROUND ::: Studies examining the stump/socket interface stresses have been restricted to unsupported stance and natural gait, i.e. walking at a comfortable speed on flat and straight walkway. However, the pressure behaviour as to the interface in unilateral transtibial amputees during walking on stairs, slope and non-flat road is unclear. ::: ::: ::: METHODS ::: Pressure distribution changes at multiple points, expressed as mean peak stump/socket interface pressure, mean pressure level over 90% of peak pressure, time in which pressure exceeded 90% of peak pressure and time-pressure integral at the period of sustained sub-maximal load, were measured during natural ambulating and walking on stairs, slope and non-flat road. ::: ::: ::: FINDINGS ::: Compared with natural gait, the mean peak pressure and sustained sub-maximal load increase notably over the patellar tendon during walking on stairs and non-flat road, and however decrease or change insignificantly at the patellar tendon on slope and over other measured areas in all conditions; moreover the time period of sustained sub-maximal load changes remarkably, except over the patellar tendon during walking up slope and over the popliteal area on non-flat road; finally, the time-pressure integral in the time period of sustained sub-maximal load changes considerably, except at the patellar tendon during walking up slope. ::: ::: ::: INTERPRETATION ::: The pressure characteristics during natural ambulating seem not to be highly predictive of what occurs in the conditions of walking on stairs, slope and non-flat road, which leads to significant increase in amplitude domain of tissue loading only at the patellar tendon, and however to remarkable changes in temporal sequences of tissue (un-)loading almost in all measured regions.
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paper_title: An experimental study of the interface pressure profile during level walking of a new suspension system for lower limb amputees.

paper_content:

BACKGROUND ::: Different suspension systems that are used within prosthetic devices may alter the distribution of pressure inside the prosthetic socket in lower limb amputees. This study aimed to compare the interface pressure of a new magnetic suspension system with the pin/lock and Seal-In suspension systems. ::: ::: ::: METHODS ::: Twelve unilateral transtibial amputees participated in the study. The subjects walked on a level walkway at a self-selected speed. The resultant peak pressure with the three different suspension systems was recorded using F-socket transducers. ::: ::: ::: FINDINGS ::: There were significant statistical differences between the three studied suspension systems. Pair-wise analyses revealed that the mean peak pressure (kPa) was lower with the magnetic system than it was with the pin/lock system over the anterior and posterior aspects during one gait cycle (89.89 vs. 79.26 and 47.22 vs. 26.01, respectively). Overall, the average peak pressure values were higher with the Seal-In system than they were with the new magnetic lock and pin/lock system. ::: ::: ::: INTERPRETATION ::: The new magnetic system might reduce the pressure within the prosthetic socket in comparison to the pin/lock and Seal-In system during one gait cycle. This is particularly important during the swing phase of gait and may reduce the pain and discomfort at the distal residual limb in comparison to the pin/lock system.
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paper_title: Interface Stress in Socket/Residual Limb with Transtibial Prosthetic Suspension Systems During Locomotion on Slopes and Stairs

paper_content:

OBJECTIVE: This study aimed to compare the effects of different suspension methods on the interface stress inside the prosthetic sockets of transtibial amputees when negotiating ramps and stairs. DESIGN: Three transtibial prostheses, with a pin/lock system, a Seal-In system, and a magnetic suspension system, were created for the participants in a prospective study. Interface stress was measured as the peak pressure by using the F-socket transducers during stairs and ramp negotiation. RESULTS: Twelve individuals with transtibial amputation managed to complete the experiments. During the stair ascent and descent, the greatest peak pressure was observed in the prosthesis with the Seal-In system. The magnetic prosthetic suspension system caused significantly different peak pressure at the anterior proximal region compared with the pin/lock (P = 0.022) and Seal-In (P = 0.001) during the stair ascent. It was also observed during the stair descent and ramp negotiation. CONCLUSIONS: The prostheses exhibited varying pressure profiles during the stair and ramp ascent. The prostheses with the pin/lock and magnetic suspension systems exhibited lower peak pressures compared with the Seal-In system. The intrasystem pressure distribution at the anterior and posterior regions of the residual limb was fairly homogenous during the stair and ramp ascent and descent. Nevertheless, the intrasystem pressure mapping revealed a significant difference among the suspension types, particularly at the anterior and posterior sensor sites.
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paper_title: Standing interface stresses as a predictor of walking interface stresses in the trans-tibial prosthesis

paper_content:

Interface pressures and shear stresses within the socket, in standing and walking, were measured for two unilateral, male, trans-tibial amputee subjects, during two sessions each. The ratios of equal weight-bearing standing stresses to peak walking stresses showed regional variation, ranging from 0.24:1 for pressure over the anterior region to 1.01:1 for resultant interface shear stress over the lateral region. Interface stresses in standing were only moderate predictors of peak walking stresses. The best correlation coefficient between standing in full weight-bearing and peak walking stress was 0.88 for pressure over the lateral region. As the amputees progressed from minimal to full weight-bearing in standing, and then to walking, the interface stresses increased in a nonlinear fashion, consistent with the assumption that the anterior tibia provides much resistance to the bending moment in the sagittal plane during walking.
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paper_title: Measurement of stresses in three orthogonal directions at the residual limb-prosthetic socket interface

paper_content:

Transducers were developed to measure stresses in three orthogonal directions applied on a below-knee amputee residual limb within a prosthetic socket during walking. Strain-gage measurement techniques were used for all three orthogonal directions. Instrumentation error for four transducers averaged less than 4.2% full-scale output (FSO) for the normal direction and less than 0.9% FSO for shear directions. Measurements from amputee subjects collected during walking trials are presented. >
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paper_title: The patellar tendon bar! Is it a necessary feature?

paper_content:

The purpose of this investigation was to vary the load on the patellar tendon bar and to study the subsequent effect this has on the pattern of the pressure distribution at the stump-socket interface. Ten male subjects from the Southern General Hospital in Glasgow, UK participated in this study. Measuring systems utilising strain gauge and electrohydraulic technologies were designed, developed and constructed to enable pressure measurements to be conducted. One transducer, the patellar tendon (PT) transducer, was attached to the patellar tendon bar of the socket such that the patellar tendon bar was capable of being translated by +/-10 mm towards or away from the tendon. The results of this study showed that the position of the patellar tendon bar had no significant effect on the pressure distribution around the socket indicating that it is an unnecessary feature, which, we propose, may be eliminated during manufacture of a trans-tibial socket.
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paper_title: Negative pressures during swing phase in below-knee prostheses with rubber sleeve suspension.

paper_content:

Negative pressures in the small space between the distal stump and the below-knee prosthetic socket were measured during swing phase for a series of nine subjects. A molded rubber sleeve connecting the prosthesis and the thigh was found to enhance this effect so that suction suspension occurred during the entire swing phase. Deterioration of the suction occurred when the sleeve was intentionally pierced, and when other suspensions such as a suprapatellar cuff or thigh band were tested. The findings indicate that the total-contact socket, gel liner and elastic sleeve combine to create suction in the below-knee socket which improves overall comfort and function for the patient in using the prosthesis.
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paper_title: Transducers for the determination of the pressure and shear stress distribution at the stump—socket interface of trans-tibial amputees

paper_content:

Recent developments in prosthetic socket design have created renewed interest in monitoring the stress distribution at the socket-residual limb interface. Although a few devices for measuring pressure can be found in the literature, none are capable of measuring reliably in areas of high curvature, such as the important area at the patellar tendon bar. Furthermore, few devices can record shear stress, thought to be critical in causing tissue damage. In order to address these issues two new transducers have been designed and evaluated. One design allows the simultaneous recording of the normal and shear stresses at various points of the socket walls, while the other is capable of measuring the three components of the force applied on the patellar tendon. The latter design incorporates a feature that permits displacement of the patellar tendon bar, in order to study the effect of various amounts of indentation of the tendon on the stress distribution around the residual limb. Both transducers were calibrated using dead weights and special jigs to ensure accurate loading conditions. Under laboratory bench conditions the normal-shear force transducer showed: 2.03 per cent full scale output (FSO) hysteresis error for shear stress direction, 1.65 per cent FSO for normal direction; 99.56 per cent FSO overall accuracy for shear direction, and within 99.64 per cent FSO for normal direction; and for the patellar tendon transducer 1.53 per cent FSO hysteresis error for shear direction, 1.85 per cent FSO for shear stress direction; 99.65 per cent FSO overall accuracy for shear direction, and 99.58 per cent FSO for normal direction. During an amputee walking trial the transducers showed 92 per cent to 97 per cent repeatability. The two new transducers were used in conjunction with two other types of transducers, previously designed at the University of Strathclyde, in a series of tests on ten trans-tibial amputees. Sample results for walking activities and a summary of maximum stresses recorded are presented.
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paper_title: Interface pressures and shear stresses at thirteen socket sites on two persons with transtibial amputation.

paper_content:

Residual limb/prosthetic socket interface pressures and shear stresses were measured at 13 sites on two subjects with unilateral transtibial amputation (TTA) using total-contact patellar-tendon-bearing prostheses. Maximal interface stresses during stance phase for each of 13 transducer sites were determined, then means for all steps calculated. Maximal pressure and resultant shear stress-during stance phase were shown at anterior distal or mid-limb sites and the maxima occurred during the first 50% of stance phase. Anterior medial and lateral proximal sites showed their greatest pressure during the second 50%. At lateral mid-limb and popliteal fossa sites, resultant shear stress directions suggest that soft tissue was displaced toward the socket brim during weight-bearing. Results also suggest that skin across the distal tibial crest was in tension at the times of the first and second peaks in the shank axial force-time curve in all sessions. Significant differences (p 3 weeks apart were apparent for both subjects.
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paper_title: Effects of alignment on interface pressure for transtibial amputee during walking

paper_content:

Studies examining interface pressure between residual limb and prosthetic socket have been restricted to unsupported stance and natural gait. However, the mechanical behavior at interface for unilateral transtibial amputees during walking when the prosthesis is misaligned is unclear. One male subject with transtibial amputation volunteers for the study. Interface pressures over five sites are measured under three sagittal alignment settings. MP (mean peak interface pressure), TP90+ (time in which pressure exceeded 90% of peak pressure) and TPI90+ (time --- pressure integral at the period of sustained sub-maximal load) are discussed for each alignment setting. compared with optimal alignment, the trend of interface pressure, the mean peak pressure do not change much, but the duration of sub-maximal pressure remarkably, except that at the patellar tendon, and finally the TPI90+ changes considerably with different alignment settings. The results offer the clinician and paramedical staff further insight in residual limb/socket interface mechanics in the transtibial amputation patients and provide potentially useful information for socket design and prosthesis fitting.
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paper_title: Tactile sensing for dexterous in-hand manipulation in robotics-A review

paper_content:

Abstract As the field of robotics is expanding from the fixed environment of a production line to complex human environments, robots are required to perform increasingly human-like manipulation tasks, moving the state-of-the-art in robotics from grasping to advanced in-hand manipulation tasks such as regrasping, rotation and translation. To achieve advanced in-hand manipulation tasks, robotic hands are required to be equipped with distributed tactile sensing that can continuously provide information about the magnitude and direction of forces at all contact points between them and the objects they are interacting with. This paper reviews the state-of-the-art in force and tactile sensing technologies that can be suitable within the specific context of dexterous in-hand manipulation. In previous reviews of tactile sensing for robotic manipulation, the specific functional and technical requirements of dexterous in-hand manipulation, as compared to grasping, are in general not taken into account. This paper provides a review of models describing human hand activity and movements, and a set of functional and technical specifications for in-hand manipulation is defined. The paper proceeds to review the current state-of-the-art tactile sensor solutions that fulfil or can fulfil these criteria. An analytical comparison of the reviewed solutions is presented, and the advantages and disadvantages of different sensing technologies are compared.
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paper_title: Clinical measurement of normal and shear stresses on a trans-tibial stump: Characteristics of wave-form shapes during walking

paper_content:

Stresses on the surface of a stump within a prosthetic socket during walking can potentially traumatize stump tissues. To gain insight into stresses and design parameters that affect them, normal and shear interface stresses were measured on three unilateral trans-tibial amputee subjects during walking trials. During stance phase repeated characteristics in wave-form shapes from different subjects were apparent. They included "loading delays", "high frequency events (HFE's)", "first peaks", "valleys", "second peaks", and "push-off". Characteristics did not necessarily occur at the same time from one step to the next but their timings matched well with events in shank force and moment data which were collected simultaneously. For "plantarflexion" and "dorsiflexion" alignment changes, the above wave-form characteristics were still present but their timings within the stance phase changed. The physical meaning and relevance of the characteristics to stump tissue mechanics are discussed.
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paper_title: Pressure distribution at the stump/socket interface in transtibial amputees during walking on stairs, slope and non-flat road.

paper_content:

BACKGROUND ::: Studies examining the stump/socket interface stresses have been restricted to unsupported stance and natural gait, i.e. walking at a comfortable speed on flat and straight walkway. However, the pressure behaviour as to the interface in unilateral transtibial amputees during walking on stairs, slope and non-flat road is unclear. ::: ::: ::: METHODS ::: Pressure distribution changes at multiple points, expressed as mean peak stump/socket interface pressure, mean pressure level over 90% of peak pressure, time in which pressure exceeded 90% of peak pressure and time-pressure integral at the period of sustained sub-maximal load, were measured during natural ambulating and walking on stairs, slope and non-flat road. ::: ::: ::: FINDINGS ::: Compared with natural gait, the mean peak pressure and sustained sub-maximal load increase notably over the patellar tendon during walking on stairs and non-flat road, and however decrease or change insignificantly at the patellar tendon on slope and over other measured areas in all conditions; moreover the time period of sustained sub-maximal load changes remarkably, except over the patellar tendon during walking up slope and over the popliteal area on non-flat road; finally, the time-pressure integral in the time period of sustained sub-maximal load changes considerably, except at the patellar tendon during walking up slope. ::: ::: ::: INTERPRETATION ::: The pressure characteristics during natural ambulating seem not to be highly predictive of what occurs in the conditions of walking on stairs, slope and non-flat road, which leads to significant increase in amplitude domain of tissue loading only at the patellar tendon, and however to remarkable changes in temporal sequences of tissue (un-)loading almost in all measured regions.
---
paper_title: Comparison of interface pressures with pin and suction suspension systems.

paper_content:

A common mode of limb suspension for transtibial amputees is the pin liner/shuttle lock system. Despite its popularity, some clinicians question its use because of observed daily and chronic changes to the residual limb. For this study, we measured limb interface pressures during ambulation with pin and suction suspension systems. No pressure differences were seen between the modes of suspension during stance phase. However, during swing phase, pin suspension maintained an average occlusive compressive pressure of 6.7 kPa on the proximal tissues, as compared to the subocclusive pressure of 1.1 kPa with suction suspension. Simultaneously, pin suspension elevated the peak magnitude of suction to -39.5 kPa at the distal residual limb, compared to -26.1 kPa with suction suspension. During swing phase, the pin liner squeezes proximally while creating a large suction distally on the residual limb and is the likely cause of daily and chronic skin changes observed in pin users.
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paper_title: Stump/socket pressure profiles of the pressure cast prosthetic socket

paper_content:

Abstract Objective. The aim was to evaluate stump/socket interface pressure in amputees wearing a socket developed by a pressure casting system. Design. Five unilateral transtibial amputees wore a pressure cast socket and walked at a self-selected speed. Background. The socket produces equally distributed pressure at the stump/socket interface, deviating from the conventional belief that pressure varies in proportion to the pain threshold of different tissues in the stump. Methods. The socket was fabricated while the subject placed his stump in a pressure chamber. Pressure was applied while he adopted a normal standing position. A specially built strain gauged type pressure transducer was used for measuring pressure distribution. Pressure and gait parameters were measured simultaneously while the subjects were standing and walking. Results and conclusion. The pressure cast technique was able to provide comfortable fitting sockets. A hydrostatic pressure profile was not evident during standing or gait. Results also showed that no standard pressure profile for the pressure cast socket was observed. This was expected as no rectifications were done on the pressure cast socket. Pressure profiles at 10%, 25% and 50% of gait cycle did not correlate with the pressure profiles previously proposed. Relevance The hydrostatic theory is an attractive concept in socket design as it produces a stump/socket pressure profile that is evenly distributed. Furthermore, it is a method that is easily implemented, independent of a prosthetist’s skill and experience and reduces manufacturing time. However, there is still controversy surrounding the efficacy of this hydrostatic theory.
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paper_title: Socket/stump interface dynamic pressure distributions recorded during the prosthetic stance phase of gait of a trans-tibial amputee wearing a hydrocast socket

paper_content:

Force sensing resistors (FSR) have been used to measure dynamic stump/socket interface pressures during the gait of a trans-tibial amputee. A total of 350 pressure sensors were attached to the inner wall of a hydrocast socket. Data were sampled at 150Hz during approximately 0.8 seconds of prosthetic stance of gait. The dynamic pressure distributions within a hand cast socket reported by Convery and Buis (1998) are compared with those monitored within a hydrocast socket for the same amputee. The pressure gradients within the hydrocast socket are less than that of the hand cast Patellar-Tendon-Bearing (PTB) socket. The proximal “ring” of high pressure in the hand cast PTB socket is replaced with a more distal pressure in the hydrocast socket.
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paper_title: Comparative study between patellar-tendon-bearing and pressure cast prosthetic sockets

paper_content:

Abstract— This study compared the pressure distribution atthe residual limb and socket interface in amputees wearing apressure cast (PCast) socket system with amputees wearing thepatellar-tendon-bearing (PTB) socket. The PCast systemrequires the subject to place his or her residual limb in a pres-sure chamber. Pressure is applied to the residual limb while thesubject adopts a normal standing position. Four unilateral maleamputees were fitted with both PTB and PCast sockets. Usinga specially built strain-gauge-type pressure transducer, werecorded residual limb and socket pressure profiles for eachsubject wearing the two types of sockets during standing andwalking. While some subjects exhibited similar anterior-posterior or medial-lateral pressure profiles for both prosthe-ses, especially during push-off, other subjects exhibited highpressure distally in the PCast so cket or higher-pressure concen-tration at the proximal region in the PTB socket. Key words: biomechanics, pressure, prosthesis, residual limb,socket, transtibial amputees.
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paper_title: Dynamic interface pressure distributions of two transtibial prosthetic socket concepts.

paper_content:

In this study, we investigated and compared the dynamic interface pressure distribution of hands-off and hands-on transtibial prosthetic systems by means of pressure mapping. Of the 48 established unilateral amputees recruited, half (n = 24) had been wearing pressure-cast prostheses (IceCast Compact) and the other half (n = 24) had been wearing hand-cast sockets of the patellar tendon bearing design. We measured the dynamic pressure profile of more than 90% of the area within each prosthetic socket by means of four Tekscan F-Scan socket transducer arrays. We compared the interface pressure between socket concepts. We found that the distribution of dynamic pressure at the limb-socket interface was similar for the two intervention (socket prescription) groups. However, a significant difference was found in the magnitude of the interface pressure between the two socket concepts; the interface pressures recorded in the hands-off sockets were higher than those seen in the hands-on concept. Despite the differences in interface pressure, the level of satisfaction with the sockets was similar between subject groups. The sockets instrumented for this study had been in daily use for at least 6 months, with no residual-limb health problems.
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paper_title: Conventional patellar-tendon-bearing (PTB) socket/stump interface dynamic pressure distributions recorded during the prosthetic stance phase of gait of a transtibial amputee

paper_content:

Force sensing resistors (FSR) have been used to measure dynamic stump/socket interface pressures during the gait of a trans-tibial amputee. A total of 350 pressure sensor cells were attached to the inner wall of a patellar-tendon-bearing (PTB) socket. Data was sampled at 150 Hz during the approximate 0.8 seconds of prosthetic stance of gait. A total of 42,000 pressures were recorded during a single prosthetic stance. This paper describes the distribution of the pressure patterns monitored during the prosthetic stance phase of gait.
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paper_title: Comparison of interface pressures with pin and suction suspension systems.

paper_content:

A common mode of limb suspension for transtibial amputees is the pin liner/shuttle lock system. Despite its popularity, some clinicians question its use because of observed daily and chronic changes to the residual limb. For this study, we measured limb interface pressures during ambulation with pin and suction suspension systems. No pressure differences were seen between the modes of suspension during stance phase. However, during swing phase, pin suspension maintained an average occlusive compressive pressure of 6.7 kPa on the proximal tissues, as compared to the subocclusive pressure of 1.1 kPa with suction suspension. Simultaneously, pin suspension elevated the peak magnitude of suction to -39.5 kPa at the distal residual limb, compared to -26.1 kPa with suction suspension. During swing phase, the pin liner squeezes proximally while creating a large suction distally on the residual limb and is the likely cause of daily and chronic skin changes observed in pin users.
---
paper_title: Comparative analysis of below-knee prosthetic socket liner materials

paper_content:

Four materials used in lining prosthetic sockets were compared for their potential usefulness in below-knee applications. Tests carried out included determinations of resistance to compression, resistance to flexural abrasion and coefficients (static and dynamic) of friction. These tests were designed, respectively, to assess changes occurring during end-use brought about by extensive application of compressive or shear force, and to predict the ability to retain contact with the body and socket. Of the four materials in the study (Bock-Lite, Pedilin, polyurethane and silicone), Bock-Lite and silicone had high compression resistance, Bock-Lite had good resistance to flexural abrasion, and polyurethane and silicone had high coefficients of frictional resistance. Thus, Bock-Lite wild be the most durable of the four materials but, since it had the lowest fictional coefficient, it may slip in use. Conversely, silicone and polyurethane, which will be retained in position me easily, are easily torn or compresse...
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paper_title: Quantification of prosthetic outcomes: elastomeric gel liner with locking pin suspension versus polyethylene foam liner with neoprene sleeve suspension.

paper_content:

For this randomized crossover trial, we compared two common transtibial socket suspension systems: the Alpha liner with distal locking pin and the Pe-Lite liner with neoprene suspension sleeve. Our original hypotheses asserted that increased ambulatory activity, wear time, comfort, and satisfaction would be found with the elastomeric suspension system. Thirteen subjects completed the study. Following 2.5-month accommodation to each condition, ambulatory activity was recorded (steps/minute for 2 weeks), and subjects completed three questionnaires specific to prosthesis use and pain: the Prosthesis Evaluation Questionnaire (PEQ), a Brief Pain Inventory (BPI) excerpt, and the Socket Comfort Score (SCS). Upon completion, subjects selected their favored system for continued use. Ten subjects preferred the Pe-Lite and three the Alpha. Subjects spent 82% more time wearing the Pe-Lite and took 83% more steps per day. Ambulatory intensity distribution did not differ between systems. No statistically significant differences were found in questionnaire results. Subject feedback for each system was both positive and negative.
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paper_title: Dermatologic conditions associated with use of a lower-extremity prosthesis.

paper_content:

OBJECTIVES ::: To document the frequency of skin problems among lower-limb prosthesis users and to assess for factors associated with skin problems among patients using a prosthesis. ::: ::: ::: DESIGN ::: Six-year retrospective chart review. ::: ::: ::: SETTING ::: An outpatient amputee clinic at a regional, referral rehabilitation hospital in Canada. ::: ::: ::: PARTICIPANTS ::: Seven hundred forty-five subjects with a total of 828 lower-extremity amputations participated. Subjects were included if they had a lower-extremity amputation and used a prosthesis for ambulation or transfers. ::: ::: ::: INTERVENTIONS ::: Not applicable. ::: ::: ::: MAIN OUTCOME MEASURES ::: The presence or absence of a skin problem. Descriptive and nonparametric statistics were used to analyze data. ::: ::: ::: RESULTS ::: Three hundred thirty-seven residual limbs (40.7%) had at least 1 skin problem. Adjusted odds ratios showed that amputation level, being employed, type of walking aid, and absence of peripheral vascular disease (as a comorbidity) were independently associated with the presence of at least 1 skin problem ( P <.05). CONCLUSIONS; Dermatologic conditions are a frequent complication for the lower-extremity amputee who uses a prosthesis. The results suggest that more active amputees have an increased risk for developing skin problems. Further study in this area is warranted.
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paper_title: Testing of elastomeric liners used in limb prosthetics: classification of 15 products by mechanical performance.

paper_content:

The mechanical properties of 15 elastomeric liner products used in limb prosthetics were evaluated under compressive, frictional, shear, and tensile loading conditions. All testing was conducted at load levels comparable to interface stress measurements reported on transtibial amputee subjects. For each test configuration, materials were classified into four groups based on the shapes of their response curves. For the 15 liners tested, there were 10 unique classification sets, indicating a wide range of unique materials. In general, silicone gel liners classified within the same groups thus were quite similar to each other. They were of lower compressive, shear, and tensile stiffness than the silicone elastomer products, consistent with their lightly cross-linked, high-fluid content structures. Silicone elastomer products better spanned the response groups than the gel liners, demonstrating a wide range of compressive, shear, and tensile stiffness values. Against a skin-like material, a urethane liner had the highest coefficient of friction of any liner tested, although coefficients of friction values for most of the materials were higher than interface shear:pressure ratios measured on amputee subjects using Pelite liners. The elastomeric liner material property data and response groupings provided here can potentially be useful to prosthetic fitting by providing quantitative information on similarities and differences among products.
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paper_title: Prosthetic Liners for Lower Limb Amputees: A Review of the Literature

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Prosthetic liners exist to improve amputee safety and comfort by adding a cushioning layer between the residual limb and the prosthetic socket. Many choices in liner technology are available, and clinicians often rely on personal intuition and experience to choose which liners are appropriate for which patients. The purpose of this study was to examine the literature to find what scientific evidence exists to inform prescription practices. 'Prosthetic liner' was used as a search term in the Web of Science and PubMed research databases. Fourteen scientific articles met the eligibility criteria and are discussed in this review. The results of this review suggest that there is little scientific evidence to inform prosthetic liner prescription practices. Liner material properties have been well-studied, but their influence on in vivo performance is not well understood. Understanding liner effect on function would be an area of great usefulness.
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paper_title: Clinical investigation of the interface pressure in the trans-tibial socket with Dermo and Seal-In X5 liner during walking and their effect on patient satisfaction

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Abstract Background The interface pressure between the residual limb and prosthetic socket has a significant effect on an amputee's satisfaction and comfort. Liners provide a comfortable interface by adding a soft cushion between the residual limb and the socket. The Dermo and the Seal-In X5 liner are two new interface systems and, due to their relative infancy, very little are known about their effect on patient satisfaction. The aim of this study was to compare the interface pressure with these two liners and their effect on patient satisfaction. Methods Nine unilateral transtibial amputees participated in the study. Two prostheses were fabricated for each amputee, one with the Seal-In liner and one with the Dermo liner. Interface pressure was measured at the anterior, posterior, medial and lateral regions during walking on the level ground. Each subject filled in a Prosthetic Evaluation Questionnaire (PEQ) regarding the satisfaction with the two liners. Findings The mean peak pressures with the Seal-In liner was 34.0% higher at the anterior, 24.0% higher at the posterior and 7.0% higher at the medial regions of the socket ( P = 0.008, P = 0.046, P = 0.025) than it was with the Dermo Liner. There were no significant differences in the mean peak pressures between the two liners at the lateral regions. In addition, significant difference was found between the two liners both for satisfaction and problems ( P Interpretation There was less interface pressure between the socket and the residual limb with the Dermo liner. The results indicated that the Dermo liner provides more comfort in the socket than the Seal-In liner.
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paper_title: An experimental study of the interface pressure profile during level walking of a new suspension system for lower limb amputees.

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BACKGROUND ::: Different suspension systems that are used within prosthetic devices may alter the distribution of pressure inside the prosthetic socket in lower limb amputees. This study aimed to compare the interface pressure of a new magnetic suspension system with the pin/lock and Seal-In suspension systems. ::: ::: ::: METHODS ::: Twelve unilateral transtibial amputees participated in the study. The subjects walked on a level walkway at a self-selected speed. The resultant peak pressure with the three different suspension systems was recorded using F-socket transducers. ::: ::: ::: FINDINGS ::: There were significant statistical differences between the three studied suspension systems. Pair-wise analyses revealed that the mean peak pressure (kPa) was lower with the magnetic system than it was with the pin/lock system over the anterior and posterior aspects during one gait cycle (89.89 vs. 79.26 and 47.22 vs. 26.01, respectively). Overall, the average peak pressure values were higher with the Seal-In system than they were with the new magnetic lock and pin/lock system. ::: ::: ::: INTERPRETATION ::: The new magnetic system might reduce the pressure within the prosthetic socket in comparison to the pin/lock and Seal-In system during one gait cycle. This is particularly important during the swing phase of gait and may reduce the pain and discomfort at the distal residual limb in comparison to the pin/lock system.
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paper_title: Literature review of the possible advantages of silicon liner socket use in trans-tibial prostheses

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The silicon liner socket has been used in the trans-tibial prosthesis since the 1980s. Silicon liner sockets are sleeves of silicon material that are rolled onto the stump and fix the prosthesis to it. The producers of the liners propagate many advantages in their use i.e. better suspension of the prosthesis, protection of the stump skin and improved cosmetic appearance. This review was performed to find objective documentation in the literature in support of the advantages in prosthetic fitting and use of silicon liners. A medline search was performed with the key words: “silicon liner socket, Icelandic Roll On Silicon Socket (ICEROSS), trans-tibial prosthesis, lower leg prosthesis and stump sockets”. Six articles remained after application of the selection criteria. In two studies clinical examination was done while in the rest questionnaires were used to collect data. The indication for amputation varied from vascular insufficiency, diabetes mellitus and infection to trauma. Most studies mentioned improved prosthetic suspension compared to the conventional supracondylar fitting. Also the walking performance improved with less use of walking aids. There were reports of positive but also negative effects on the skin such as excessive perspiration and itching. Patients had a general preference in prosthetic appearance in favour of the prosthesis with a silicon liner. Further research is needed with the use of objective clinical parameters and a homogenous study group objectively to find advantages in the use of the silicon liner socket in the trans-tibial prosthesis.
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paper_title: Polyurethane gel liner usage in the Oxford Prosthetic Service

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The objective was to investigate which lower limb amputees are using Alpha polyurethane gel liners and the effects of these on comfort and suspension of their prosthesis. A retrospective study was carried out of case records of all patients issued with Alpha cushion and locking liners between 1997 and the end of January 1999. The type of liner used was compared with age, sex, level and cause of amputation, time since amputation, comfort and suspension. Modified Stanmore/Harold-Wood mobility grades; duration of use and number of liners issued per patient were recorded. Sixteen (16) patients were identified who had been prescribed Alpha cushion liners. Improved comfort was reported by all. Forty (40) patients were identified who had been prescribed Alpha locking liners. Twenty (20) of these reported improved comfort and 10 improved suspension. The average time since amputation was 18.5 years for those using cushion liners and 14.1 years for locking liner users. Fifty-two (52) of all 56 patients using Alpha cushion and locking liners had mobility grades of 4 or more. Trauma was the most common cause of amputation. This group is a relatively mobile group of amputees. All those using cushion liners reported improved comfort. Some of the locking liner users reported improved comfort and suspension but this was not universally the case.
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paper_title: A questionnaire survey of the effect of different interface types on patient satisfaction and perceived problems among trans-tibial amputees

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The objectives were to investigate the effect of three different interface types on consumer satisfaction and perceived problems among trans-tibial amputees in the Netherlands. A postal questionnaire (based on the Prosthesis Evaluation Questionnaire) was sent to 353 patients. Responders were classified in three groups of interface types: polyethylene foam (PEF) inserts, silicone liners (SIL), and polyurethane liners (PUL). Differences concerning satisfaction and problems between interface types were computed and adjusted for potential confounding by age, gender, reason for amputation and time since first prosthesis. A total of 220 patients responded (62%). Patients wearing liners reported a significantly poorer durability and higher maintenance time compared with patients using PEF inserts. Sum-scores for satisfaction or problems did not show any significant differences between groups. Analysis of individual items showed a significant difference only for satisfaction with sitting and with walking on uneven terrain in favour of PEF inserts. In contrast to most studies, interface type was included as a possible determinant of customer use, satisfaction, and perceived problems. The perceived differences between the three suspension types are to a large extent small and non-significant. The findings do not support liner prescription as a matter of course for all trans-tibial amputees. A careful analysis of patients' preferences should be made to determine the best course of action. Further studies, preferably prospective, need to be conducted to determine which systems are most comfortable and offer least complaints.
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paper_title: Dynamic interface pressure distributions of two transtibial prosthetic socket concepts.

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In this study, we investigated and compared the dynamic interface pressure distribution of hands-off and hands-on transtibial prosthetic systems by means of pressure mapping. Of the 48 established unilateral amputees recruited, half (n = 24) had been wearing pressure-cast prostheses (IceCast Compact) and the other half (n = 24) had been wearing hand-cast sockets of the patellar tendon bearing design. We measured the dynamic pressure profile of more than 90% of the area within each prosthetic socket by means of four Tekscan F-Scan socket transducer arrays. We compared the interface pressure between socket concepts. We found that the distribution of dynamic pressure at the limb-socket interface was similar for the two intervention (socket prescription) groups. However, a significant difference was found in the magnitude of the interface pressure between the two socket concepts; the interface pressures recorded in the hands-off sockets were higher than those seen in the hands-on concept. Despite the differences in interface pressure, the level of satisfaction with the sockets was similar between subject groups. The sockets instrumented for this study had been in daily use for at least 6 months, with no residual-limb health problems.
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paper_title: Interface pressure in transtibial socket during ascent and descent on stairs and its effect on patient satisfaction

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Abstract Background Transtibial amputees encounter stairs and steps during their daily activities. The excessive pressure between residual limb/socket may reduce the walking capability of transtibial prosthetic users during ascent and descent on stairs. The purposes of the research were to evaluate the interface pressure between Dermo (shuttle lock) and Seal-In X5 (prosthetic valve) interface systems during stair ascent and descent, and to determine their satisfaction effects on users. Methods Ten amputees with unilateral transtibial amputation participated in the study. Interface pressure was recorded with F-socket transducer (9811E) during stair ascent and descent at self-selected speed. Each participant filled in a questionnaire about satisfaction and problems encountered with the use of the two interface systems. Findings The resultant mean peak pressure (kPa) was significantly lower for the Dermo interface system compared to that of the Seal-In X5 interface system at the anterior, posterior and medial regions during stair ascent (63.14 vs. 80.14, 63.14 vs. 90.44, 49.21 vs. 66.04, respectively) and descent (67.11 vs. 80.41, 64.12 vs. 88.24, 47.33 vs. 65.11, respectively). Significant statistical difference existed between the two interface systems in terms of satisfaction and problems encountered ( P Interpretation The Dermo interface system caused less pressure within the prosthetic socket compared to the Seal-In X5 interface system during stair negotiation. The qualitative survey also showed that the prosthesis users experienced fewer problems and increased satisfaction with the Dermo interface system.
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paper_title: Comparative Study between Dermo, Pelite, and Seal-In X5 Liners: Effect on Patient's Satisfaction and Perceived Problems

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PURPOSE ::: This study aimed to compare the effect of satisfaction and perceived problems between Pelite, Dermo with shuttle lock, and Seal-In X5 liners on the transtibial amputees. ::: ::: ::: MATERIAL AND METHODS ::: A total of thirty transtibial amputees (17 male, 13 female) volunteered to take part in this research. Two prostheses were fabricated for each participant. Prosthetic Evaluation Questionnaire (PEQ) was filled in by the participants with the three liners. ::: ::: ::: RESULTS ::: The statistics highlight that Dermo liner showed significantly higher score (P = 0.05) in walking, walking on uneven surfaces, stairs walking, fitting, donning/doffing, sitting, suspension, and overall satisfaction with Dermo liner compared with Seal-In X5 and Pelite liners. Overall satisfaction was 34% higher with Dermo liner than Seal-In X5 liner and 28% higher than Pelite liner. Participants reported less problems with Dermo liner and significant differences (P < 0.05) were recorded between the three liners in sweating, skin irritation, frustration, and pain compared with Seal-In X5 and Pelite liners. ::: ::: ::: CONCLUSION ::: Participants experienced high level of satisfaction and practiced fewer problems with Dermo liner. These results showed that there is good indication to believe that Dermo liner might be a good choice for transtibial users and might help the clinicians and prosthetic practitioners in selection criteria of prosthetic liners.
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paper_title: Interface Stress in Socket/Residual Limb with Transtibial Prosthetic Suspension Systems During Locomotion on Slopes and Stairs

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OBJECTIVE: This study aimed to compare the effects of different suspension methods on the interface stress inside the prosthetic sockets of transtibial amputees when negotiating ramps and stairs. DESIGN: Three transtibial prostheses, with a pin/lock system, a Seal-In system, and a magnetic suspension system, were created for the participants in a prospective study. Interface stress was measured as the peak pressure by using the F-socket transducers during stairs and ramp negotiation. RESULTS: Twelve individuals with transtibial amputation managed to complete the experiments. During the stair ascent and descent, the greatest peak pressure was observed in the prosthesis with the Seal-In system. The magnetic prosthetic suspension system caused significantly different peak pressure at the anterior proximal region compared with the pin/lock (P = 0.022) and Seal-In (P = 0.001) during the stair ascent. It was also observed during the stair descent and ramp negotiation. CONCLUSIONS: The prostheses exhibited varying pressure profiles during the stair and ramp ascent. The prostheses with the pin/lock and magnetic suspension systems exhibited lower peak pressures compared with the Seal-In system. The intrasystem pressure distribution at the anterior and posterior regions of the residual limb was fairly homogenous during the stair and ramp ascent and descent. Nevertheless, the intrasystem pressure mapping revealed a significant difference among the suspension types, particularly at the anterior and posterior sensor sites.
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paper_title: The ICEROSS concept: A discussion of a philosophy

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Prefabricated ICEROSS (Icelandic Roll On Silicone Socket) sockets have been in use in Iceland since early 1986. Use of custom-made silicone sockets began several years earlier, and a paper devoted to the subject was presented at the 1984 AOPA Assembly by the author of this article. The ICEROSS system is primarily used for suspension. At the same time the author believes it considerably improves the weight-bearing capability of the prosthesis and the interface between prosthesis and user. After being turned inside out and rolled over the stump, the silicone sleeve forces skin in a distal direction, stabilising soft tissue and minimising pistoning. Both prosthetist and user may experience some problems initially, although most can be overcome by careful socket design and skin care.
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paper_title: Silicone Suction Socket (3s) Versus Supracondylar Ptb Prosthesis with Pelite Liner: Transtibial Amputees' Preferences

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ABSTRACT The purpose of this article is to evaluate the preference of transtibial amputees for the Silicone Suction Socket (3S) versus the supracondylar PTB prosthesis with pelite liner and to explore the reasons for their preferences. Eight patients with residual-limb problems were asked to wear each type of prosthesis for a minimum of 10 weeks (except if no definitive 3S was made due to problems with the trial socket) and subsequently were asked to complete questionnaires to discuss comfort, ambulation and activities of daily life, working conditions, and sports activities with the prostheses. Two patients did not receive a definitive 3S because they could not walk comfortably on the trial socket Two of the six amputees who used both socket designs preferred the 3S, two preferred the supracondylar PTB with pelite liner, and two were satisfied with both prostheses.
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paper_title: Lower limb amputation Part 3: Prosthetics - a 10 year literature review

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This paper is intended as a follow-up to the ISPO Consensus Conference on Amputation Surgery. It reviews all the literature on lower limb prosthetics published after 1990. The review was considered under six categories: feet, knees, hips, thermoplastics, liners/suspension and computers.
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paper_title: Transtibial prosthesis suspension systems: Systematic review of literature

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BACKGROUND ::: Today a number of prosthetic suspension systems are available for transtibial amputees. Consideration of an appropriate suspension system can ensure that amputee's functional needs are satisfied. The higher the insight to suspension systems, the easier would be the selection for prosthetists. This review attempted to find scientific evidence pertaining to various transtibial suspension systems to provide selection criteria for clinicians. ::: ::: ::: METHODS ::: Databases of PubMed, Web of Science, and ScienceDirect were explored to find related articles. Search terms were as follows: "Transtibial prosthesis (32), prosthetic suspension (48), lower limb prosthesis (54), below-knee prosthesis (58), prosthetic liner (20), transtibial (193), and prosthetic socket (111)". Two reviewers separately examined the papers. Study design (case series of five or more subjects, retrospective or prospective), research instrument, sampling method, outcome measures and protocols were reviewed. ::: ::: ::: FINDINGS ::: Based on the selection criteria, 22 articles (15 prospective studies, and 7 surveys) remained. Sweat control was found to be a major concern with the available suspension liners. Donning and doffing procedures for soft liners are also problematic for some users, particularly those with upper limb weakness. Moreover, the total surface bearing (TSB) socket with pin/lock system is favored by the majority of amputees. ::: ::: ::: INTERPRETATION ::: In summary, no clinical evidence is available to suggest what kind of suspension system could have an influential effect as a "standard" system for all transtibial amputees. However, among various suspension systems for transtibial amputees, the Iceross system was favored by the majority of users in terms of function and comfort.
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Title: Techniques for Interface Stress Measurements within Prosthetic Sockets of Transtibial Amputees: A Review of the Past 50 Years of Research

Section 1: Introduction
Description 1: Introduce the increasing incidence of lower limb amputations, the importance of prosthetic sockets, and the challenges associated with their fitting and design. Explain the historical techniques used for pressure assessment and the evolution of force transducers.

Section 2: The Evolution of Transtibial Socket Designs
Description 2: Discuss the various transtibial socket designs developed over the years, including the Patellar Tendon Bearing (PTB) sockets, Total Surface Bearing (TSB) sockets, and the introduction of rapid prototyping.

Section 3: Transducer Mounting Techniques
Description 3: Describe the different techniques for mounting stress measurement transducers, such as mounting on the socket wall, inserting in the socket, and embedding in the socket wall.

Section 4: Types of Transducers
Description 4: Provide an overview of the different types of transducers used for interface stress measurements in transtibial sockets, including strain gauges, piezoresistive, capacitive, and optical sensors.

Section 5: Strain Gauge-Based Transducers
Description 5: Detail the working principles, advantages, and applications of strain gauge-based transducers in prosthetic sockets.

Section 6: Piezoresistive Transducers
Description 6: Highlight the features, structure, advantages, and disadvantages of piezoresistive transducers such as Force Sensing Resistors (FSRs).

Section 7: Capacitive Transducers
Description 7: Explain the configuration, working principles, and applications of capacitive transducers in measuring interface stresses in prosthetic sockets.

Section 8: Optical Sensors
Description 8: Discuss the introduction, development, and advantages of optical sensors such as fiber Bragg grating sensors (FBGs) for biomechanical applications, specifically in prosthetic sockets.

Section 9: Prosthetic Interface Stress Measurement in Different Socket Designs
Description 9: Summarize studies and findings concerning the measurement of interface stresses in PTB and TSB socket designs during various activities like walking and running.

Section 10: Effect of Liner Materials and Suspension Systems
Description 10: Explore the impact of different liner materials and suspension systems on prosthetic interface stress measurements and amputee satisfaction.

Section 11: Conclusions
Description 11: Summarize the key points covered in the review, highlight the significance of different measurement systems and socket designs, and suggest future research directions.