Clinical Outcomes of Unipolar Versus Bipolar Patellofemoral Fresh Osteochondral Allograft Transplantation

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/m²) 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.