Review Question - QID 210

The radiographs show a knee with significant medial compartment narrowing. A frequently tested fact is that wear associated with chronic PCL instability occurs most commonly in the patellofemoral joint and the medial compartment of the knee. A young laborer is not an ideal candidate for arthroplasty because of early wear and loosening concerns. In addition, cruciate ligaments are required for the insertion of a unicompartmental knee replacement. Isolated PCL reconstruction would not be recommended as he already has arthritis and cruciate reconstruction in a mal-aligned knee is at increased risk of failure. Either valgus producing osteotomy is reasonable, but the opening wedge tends to increase posterior tibial slope which is helpful in PCL-deficient knees.

The article by Giffin et al described that by performing an opening medial wedge osteotomy, the slope of the knee is effectively increased by about 3 degrees and this reduces posterior subluxation or sag of the tibia on the femur. This helps to accommodate for the deficient ligamentous restraint posteriorly, whereas decreasing slope may be protective in an ACL-deficient knee.