Clinical Outcomes of Patellofemoral Osteochondral Allograft Transplantation: A Prospective Analysis

Abstract

Objectives:The use of osteochondral allograft transplantation (OAG) for chondral defects of the knee is increasing, particularly for defects involving the femoral condyles. The purpose of this study was to prospectively evaluate the clinical outcomes for patients undergoing patellofemoral OAG for symptomatic chondral lesions.Methods:Consecutive patients undergoing OAG for full-thickness patella and trochlear lesions between 2007 and 2014 by two senior surgeons were analyzed. Pre- and post-operative patient reported outcomes scores were collected, with a minimum 21-month follow-up. Patient demographics, preoperative clinical data including information on prior ipsilateral knee surgeries, and intraoperative details were analyzed for all patients. Complications, reoperations, and conversion to total knee or patellofemoral arthroplasty were recorded. Statistical analysis was conducted with student’s T-tests, with P<0.05 considered significant.Results:A total of 14 patients (10 females, 4 males) with an average age of 32.8±7.5 years (range, 20-48) were identified for inclusion with an average follow-up of 3.6±1.8 years (range, 1.8-7.8) (Table 1). The average body mass index was 27.5±6.9 kg/m2. Patients experienced an average 5.4±4.2 years of symptoms prior to OAG and 100% of patients had undergone previous ipsilateral knee surgery with an average 4.1±3.5 prior procedures before undergoing patellofemoral OAG. The average defect size on the patella was 855mm2 while that on the trochlea was 322mm2. At the time of OAG, 6 (43%) patients received trochlear grafts, 6 (43%) received patellar grafts, and 2 (14%) received bipolar grafts. Nine patients (64%) received a single allograft, 3 (21%) received 2 allografts to 2 separate lesions, and 2 (14%) received grafts to 4 separate lesions. At final follow-up, there were significant improvements in Lysholm, IKDC, KOOS, WOMAC, and SF-12 Physical outcomes scores; no significant improvements were found in the SF-12 Mental subscale (Figure 1). Two patients (both female, ages 27 and 41) were considered failures as they had converted to knee arthroplasty at an average 2.7 years following OAG. Both of these patients had received allografts to the patella with lesion sizes of 506mm2 and 1800mm2, respectively.Conclusion:Osteochondral allograft transplantation of the patellofemoral joint can be considered a viable restoration procedure for patients with symptomatic chondral lesions to the trochlea and patella. At an average follow-up of 3.6 years, the majority of patients will experience significant improvements in nearly all outcomes scores, with an arthroplasty conversion rate of 14%. Additional information on this difficult-to-treat patient population, including a better understanding of risk factors for failure, prognostic factors for success, and long-term outcomes, is needed.Table 1Patient informationCaseBody Mass Index (kg/m2)Symptom Duration(yrs.)History of Failed Prior Articular Cartilage ProcedureType of Previous Cartilage Procedure# OA GraftsLocation of GraftsLesion Area (mm)Failed to TKA/PFATime to Failure (Yrs.)1 (36yo M)33.225NoN/A2Trochlea, MFC400, 225NoN/A2 (27yo M)27.123YesACI1Patella324NoN/A3 (48yo F)23.402No1Trochlea400, 225NoN/A4 (24yo M)27.609No4Trochlea, MFC (x2), LFC625, 324, 225, 625NoN/A5 (34yo M)28.322YesMFX1Trochlea/MFC Junction225NoN/A6 (24yo F)19.583.5Yes1Trochlea225NoN/A7 (30yo F)26.623No2Trochlea, MFC324, 225NoN/A8 (34yo F)33.61YesMFX4patella, trochlea, MFC x21500,254, 254, 201NoN/A9 (41yo F)20.810No1Patella506Yes2.910 (27yo F)42.62.5YesTruFit Plug, DeNovo1Patella1800Yes2.411 (37yo F)35.72YesDeNovo1Patella988NoN/A12 (33yo F)17.311YesOA Graft2Patella, Trochlea375, 300NoN/A13 (20yo F)25.16YesDeNovo, ACI1Patella975NoN/A14 (38yo F)24.415No1Patella375NoN/A