Comparable revision outcomes after unicompartmental knee arthroplasty in rheumatoid arthritis and osteoarthritis : results from the German Arthroplasty Registry.

Abstract

This study aimed to compare the risk of revision surgery between patients with rheumatoid arthritis (RA) who underwent primary unicompartmental knee arthroplasty (UKA) and those with osteoarthritis (OA). Data from the German Endoprosthesis Registry (EPRD) were used to compare 796 cases of primary UKA in RA patients with 67,653 cases in patients with OA. Revisions were classified into major (revision of at least the femoral or tibial component) and minor (no bony component revision, including only insert exchange), based on the surgical and procedural codes recorded in the register and further stratified by aseptic or septic revision. Mahalanobis matching was performed with a 1 RA to 5 OA ratio. The crude and matched cumulative risk of these procedures was analyzed using the Kaplan-Meier estimator. Statistical significance of differences was assessed using the log-rank test. At two years, the crude cumulative risk of major revision was similar between RA (3.5%) and OA patients (3.3% p = 0.860). Matched analysis showed no significant difference with patients with OA (3.1%; p = 0.650). When stratified by cause, septic and aseptic major revisions did not differ between groups. For minor revisions, the crude risk was not different between patients with RA (2.2%) and in OA (1.3%; p = 0.071); matched analysis also showed no significant difference with patients with OA (1.5%; p = 0.236). When stratified by cause, no differences were observed in septic or aseptic minor revisions. Comparable patterns persisted through nine years. RA does not appear to impact the risk of revision surgery compared with OA. However, the limited sample size and relatively short follow-up necessitate ongoing monitoring to determine the risk for long-term outcomes.