AJSM - 2026-04-01 - Journal Article; Comparative Study
Clinical Outcomes of Unipolar Versus Bipolar Patellofemoral Fresh Osteochondral Allograft Transplantation.
Acheampong KK, Augustin EJ, Moran TE, Atkins M, Akinleye J, Bi AS, Cole BJ, Yanke AB
Topics
Key Takeaway
Bipolar patellofemoral OCA transplantation had a 25% structural graft failure rate versus 0% for unipolar, but cumulative lesion area—not bipolarity per se—was the independent predictor of failure (OR 1.005 per mm²).
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Summary
This study compared graft failure, reoperation, and PROs between unipolar and bipolar patellofemoral OCA transplantation at minimum 2-year follow-up using a prospectively maintained institutional database. Structural failure occurred in 25% of bipolar versus 0% of unipolar knees (P=.03), but multivariable regression identified cumulative lesion area as the independent failure predictor rather than bipolarity itself. Among non-failure patients, both groups achieved statistically significant and clinically meaningful improvements in IKDC and KOOS subscores with no between-group difference in PRO achievement.
Key Limitation
The bipolar cohort contained only 12 knees, making the 25% failure rate based on 3 events and rendering all regression-derived odds ratios statistically fragile.
Original Abstract
BACKGROUND
Osteochondral allograft (OCA) transplantation in the tibiofemoral joint has been extensively studied, but limited data exist regarding outcomes after patellofemoral (PF) OCA transplantation, particularly for bipolar osteochondral lesions.
PURPOSE
To compare graft failure rates, graft reoperation rates, and patient-reported outcomes (PROs) between patients who underwent unipolar and bipolar PF OCA transplantation at the ≥2-year follow-up.
STUDY DESIGN
Cohort study; Level of evidence, 4.
METHODS
A retrospective review of a prospectively maintained institutional database identified patients who underwent PF OCA transplantations from 2015 to 2024. Patients with concomitant tibiofemoral OCA transplantation or <2 years of follow-up were excluded. Outcomes including graft failure, reoperation, and PROs were compared between patients in the unipolar and bipolar groups who underwent PF OCA transplantation. Preoperative, surgical, and postoperative variables were assessed for associations with outcomes using multivariable regression analysis.
RESULTS
A total of 36 knees (24 unipolar, 12 bipolar) from 35 of 41 (85.4%) eligible patients (68.6% female; mean age, 33.59 ± 8.10 years; mean body mass index, 29.24 ± 5.28 kg/m 2 ) were included. The mean follow-up was 3.58 ± 1.39 years (3.87 ± 1.45 years for unipolar vs 3.00 ± 1.10 for bipolar; P = .046). Groups did not differ in baseline PROs, prior surgeries ( P = .53) or cartilage repair ( P = .66), and concomitant ( P = .19) or prior ( P = .48) tubercle osteotomy. Structural graft failure was higher in bipolar lesion knees (3 [25%] bipolar vs 0 [0%] unipolar; P = .03) but notably associated with cumulative lesion area (OR, 1.005; 95% CI, 1.0004-1.0114; P = .031). Among patients without failure, both groups demonstrated significant and similar improvements in International Knee Documentation Committee (IKDC) and Knee injury and Osteoarthritis Outcome Score (KOOS) subscores at the final follow-up (all P ≤ .036), with no between-group difference in achievement of IKDC, KOOS Pain, KOOS Symptoms, and KOOS Sports clinically significant outcomes. Graft reoperation rates were similar (3 [12.5%] unipolar vs 1 [8.33%] bipolar; P > .99).
CONCLUSION
Bipolar and unipolar PF OCA transplantation both yielded excellent and comparable short- to midterm postoperative PROs, clinically significant functional improvement, and reoperation rates. Although larger cumulative bipolar lesions may indicate a higher disease burden and risk of graft failure, bipolar transplantation remained effective and clinically beneficial in most patients at the final follow-up, delaying arthroplasty and associated increased complication rates in this young patient cohort.