Long-Term Functional Outcomes and Modes of Failure of Fresh Frozen Hemicondylar Allografts: A Retrospective Cohort Study.

Background: Hemicondylar fresh frozen allografts address partial knee defects while preserving native anatomy and bone stock. This study evaluated long-term survival, failure modes, and functional outcomes following hemicondylar reconstruction.

Methods: We conducted a retrospective analysis of hemicondylar fresh frozen allograft reconstructions. Allograft failure was assessed using the Henderson classification and osteoarthritis via Kellgren-Lawrence classification. Functional outcomes were evaluated using MSTS scores and patient-reported measures, with radiographic evaluation performed preoperatively and at 1, 2, 5, and 10 years postoperatively.

Results: A total of 17 patients (13 femoral, 4 tibial allografts) with a median age of 29 years and a median follow-up of 16.9 years were included. Four patients (24%) experienced allograft failure, including two structural failures, one infection, and one soft-tissue failure. Overall allograft survival was 87.5% at 1 year, 80.8% at 2 years, and 74% at 5-20 years, with a median MSTS score of 21/30. While all patients developed progressive osteoarthritis, only six required total knee arthroplasty for symptomatic arthritis rather than allograft failure.

Conclusion: Hemicondylar allografts demonstrate acceptable long-term survival and functional outcomes, with progressive osteoarthritis/chondrolysis representing expected evolution rather than treatment failure. Structural collapse remains the predominant failure mechanism requiring removal. These findings support hemicondylar allografts as viable reconstructive options for selected patients.

Level of evidence: Level IV.