Review Question - QID 217381

This patient has a full-thickness cartilage defect of the patella that is indicated for surgical management. Involvement of the patellofemoral joint (PFJ) places this patient at increased risk of failure after an osteochondral allograft transfer (OCA).

Cartilage defects of the knee remain a clinical challenge to treat given the poor healing capabilities of articular cartilage that can result in functional impairment and development of early osteoarthritis. Nonoperative treatment consists of physical therapy, NSAIDs, weight loss, activity modification, and intraarticular hyaluronic acid viscosupplementation. Surgical treatment options include chondroplasty, bone marrow stimulation, OATs, OCA, and ACI. The choice of the procedure is based on multiple factors including size of the lesion, location, containment, involvement of subchondral bone, as well as patient factors including age, overall mechanical alignment, activity, and expectations. Given the adverse biomechanical environment of the PFJ, among other factors, higher failure rates are seen following OCA. Patella instability and mechanical alignment should be addressed before or at the time of the cartilage procedure to improve the overall outcome.

Assenmacher et al conducted a systematic review of the long-term outcomes following knee osteochondral allografts. The most common lesions were femoral condyle (67%), tibia (29%), and lastly patella (4%). The average follow-up was 12.3 years and all outcomes scores showed improvement at the final follow-up. Patellofemoral lesions were associated with decreased clinical improvement and more frequent reoperations.

Mestriner et al conducted a review of various cartilage restoration techniques for cartilage defects of the patellofemoral joint including chondroplasty, bone marrow stimulation, ACI, OAT, OCA, and particulate cartilage procedures. They provide an overview of the indications, provide some technical aspects, and review the current literature for each procedure. Lastly, they provide an algorithm to approach cartilage defects of the PFJ.

Figure A is a T2-weight sagittal and axial view of a knee showing a full-thickness cartilage defect of the lateral facet of the patella with subchondral bone edema.

Illustration A is an algorithm to approach articular cartilage defects of the PFJ based on subchondral bone involvement and the size of the defect.

Incorrect Answers
Answer 1: Male gender is not associated with higher failure rates following OCA.
Answer 2: Bipolar, not unipolar, lesions are associated with higher failure rates.
Answer 3: Outerbridge grade IV is an indication for a cartilage restoration procedure and not necessarily a risk factor.
Answer 5: Performing a tibial tubercle osteotomy to improve patella tracking should be performed in conjunction with the cartilage procedure or in a staged fashion.