Fractures: Bone Repair

Learning Objectives

  • Differentiate among the different types of fractures
  • Describe the steps involved in bone repair



Types of Fractures

Fractures are classified by their complexity, location, and other features (Figure 1). Table 1 outlines common types of fractures. Some fractures may be described using more than one term because it may have the features of more than one type (e.g., an open transverse fracture).

In this illustration, each type of fracture is shown on the right femur from an anterior view. In the closed fracture, the femur is broken in the middle of the shaft with the upper and lower halves of the bone completely separated. However, the two halves of the bones are still aligned in that the broken edges are still facing each other. In an open fracture, the femur is broken in the middle of the shaft with the upper and lower halves of the bone completely separated. Unlike the closed fracture, in the open fracture, the two bone halves are misaligned. The lower half is turned laterally and it has protruded through the skin of the thigh. The broken ends no longer line up with each other. In a transverse fracture, the bone has a crack entirely through its width, however, the broken ends are not separated. The crack is perpendicular to the long axis of the bone. Arrows indicate that this is usually caused by compression of the bone in a superior-inferior direction. A spiral fracture travels diagonally through the diameter of the bone. In a comminuted fracture, the bone has several connecting cracks at its middle. It is possible that the bone could splinter into several small pieces at the site of the comminuted fracture. In an impacted fracture, the crack zig zags throughout the width of the bone like a lightning bolt. An arrow indicates that these are usually caused by an impact that pushes the femur up into the body. A greenstick fracture is a small crack that does not extend through the entire width of the bone. The oblique fracture shown here is travelling diagonally through the shaft of the femur at about a thirty degree angle.


Table 1. Types of Fractures
Type of fracture Description
Transverse Occurs straight across the long axis of the bone
Oblique Occurs at an angle that is not 90 degrees
Comminuted Several breaks result in many small pieces between two large segments

Bone Repair


This illustration shows a left to right progression of bone repair. The break is shown in the leftmost image, where the femur has an oblique, closed fracture in the middle of its shaft. The next image magnifies the break, showing that blood has filled the area between the broken bones. Blood has also filled in around the lateral and medial sides of the break. The influx of blood causes the broken area to swell, creating a hematoma. In the next image, the hematoma has been replaced with an external callus between the two broken ends. Within the internal callus, the blood vessels have reconnected and some spongy bone has regenerated in the gap between the two bone halves. In the next image, spongy bone has completely regenerated, connecting the two broken ends, referred to as the bony callus. The external callus still remains on the lateral and medial sides of the break, as the compact bone has not yet regenerated. In the final image, the compact bone has fully regenerated, encapsulating the bony callus and completely reconnecting the two bone halves. The bone has a slight bulge at the location of the healed fracture, which is clearly shown in the final image, which shows a zoomed out image of the completely healed femur.




Eventually, the internal and external calli unite, compact bone replaces spongy bone at the outer margins of the fracture, and healing is complete. A slight swelling may remain on the outer surface of the bone, but quite often, that region undergoes remodeling (Figure 2d), and no external evidence of the fracture remains.