Knee osteotomy is surgery that removes a part of the bone of the joint of either the bottom of the femur (upper leg bone) or the top of the tibia (lower leg bone) to increase the stability of the knee. Osteotomy redistributes the weight-bearing force on the knee by cutting a wedge of bone away to reposition the knee. The angle of deformity in the knee dictates whether the surgery is to correct a knee that angles inward, known as a varus procedure, or one that angles outward, called a valgus procedure. Varus osteotomy involves the medial (inner) section of the knee at the top of the tibia. Valgus osteotomy involves the lateral (outer) compartment of the knee by shaping the bottom of the femur.
Osteotomy surgery changes the alignment of the knee so that the weight-bearing part of the knee is shifted off diseased or deformed cartilage to healthier tissue in order to relieve pain and increase knee stability. Osteotomy is effective for patients with arthritis in one compartment of the knee. The medial compartment is on the inner side of the knee. The lateral compartment is on the outer side of the knee. The primary uses of osteotomy occur as treatment for:
- Knee deformities such as bowleg in which the knee is varus-leaning (high tibia osteotomy, or HTO) and knock-knee (tibial valgus osteotomy), in which the knee is valgus leaning.
- A torn anterior cruciate ligament (ACL), which is a set of ligaments that connects the femur to the tibia behind the patella and offers stability to the knee on the left-right or medial-lateral axis. If this ligament is injured, it must be repaired by surgery. Many ACL injuries cause inflammation of the cartilage of the knee and result in bones extrusions, as well as instability of the knee due to malalignment. Osteotomy is performed to cut cartilage and increase the fit and alignment of the ends of the femur and tibia for smooth articulation. As one very common knee injury that often occurs in athletic activity, HTO is often performed when ACL surgery is used to repair the ligament. The combination of the two surgeries occurs primarily in young people who wish to return to a highly athletic life.
- Osteoarthritis that includes loss of range of motion, stiffness, and roughness of the articular cartilage in the knee joint secondary to the wear and tear of motion, especially in athletes, as well as cartilage breakdown resulting from traumatic injuries to the knee. Surgery for progressive osteoarthritis or injury-induced arthritis is often used to stave off total joint replacement.
After surgery, patients are placed in a hinged brace. Toe-touching is the only weight-bearing activity allowed for four weeks in order to allow the osteotomy to hold its place. Continuous passive motion is begun immediately after surgery and physical therapy is used to establish full range of motion, muscle strengthening, and gait training. After four weeks, patients can begin weight-bearing movement. The brace is worn for eight weeks or until the surgery site is healed and stable. X rays are performed at intervals of two weeks and eight weeks after surgery.
The usual general surgical risks of thrombosis and heart attack are possible in this open surgery. Osteotomy surgery itself involves some risk of infection or injury during the procedure. Combined surgery for ACL and osteotomy has higher morbidity rates.