Revision of unicondylar knee arthroplasty: an analysis of failure rates and contributing factors.

Background: The implantation rate of knee arthroplasty and, in particular of unicondylar knee arthroplasty (UKA), is increasing, and revision is a feared complication. The aim of this study was to identify factors influencing aseptic and septic revision that are of high interest for establishing preventive measures.

Methods: Data were collected using the German Arthroplasty Registry (EPRD). Patients with UKA were analyzed using the multiple Log-rank test with Holm's method. Septic and aseptic revisions were calculated using Kaplan-Meier estimates. In total, 300,998 cases of knee arthroplasty were identified in the registry, and 36,861 patients with UKA were analyzed with a maximum follow-up of 7 years.

Results: The primary reason for UKA revision surgery was aseptic loosening (32.5%), particularly loosening of the tibial component (19.0%), followed by infection (11.0%) and the progression of arthritis (10.0%). Over 7 years, 8.7% of UKA procedures required revision, 7.8% for aseptic causes and 0.9% for infection. Risk factors for aseptic revision included uncemented implants [hazard ratio (HR) 1.38] and low annual surgical volume (fewer than 25 UKAs/year, HR 1.86; fewer than 50 UKAs/year, HR 1.43). Significant risks for septic revision were grade III obesity (HR 1.83), male sex (HR 1.69), and high comorbidity scores (Elixhauser > 5, HR 1.67). The surgical volume did not affect septic revision rates.

Conclusion: Aseptic loosening is the primary cause of UKA revision, influenced by implant type and low surgical volume, while septic revisions are associated with patient factors such as obesity, male sex, and comorbidities. Improvements in implant selection, surgical expertise, and patient risk management may reduce revision rates.

Level of evidence: III, retrospective case-control study.