To assess the influence of rheumatoid arthritis (RA) disease activity (DA) on the risk of aseptic loosening after total hip/knee arthroplasty (THA/TKA).
We identified RA patients who underwent THA/TKA and determined their DA using the simplified disease activity index (SDAI). The risk of aseptic loosening was estimated using radiographic signs of component loosening (RCL). We performed Cox regression to estimate RCL based on SDAI, adjusting for therapy. We also investigated a cohort of 2:1 matched osteoarthritis (OA) patients as a control group without systemic inflammation.
We identified 49 RA patients with a history of THA/TKA, of whom 18 (36.7%) showed RCL. SDAI over time was significantly higher in patients with RCL (median; 25th and 75th percentile: 10.8 months; 8.6 and 15.8; vs 7.0 months; 2.7 and 15.5;p = 0.043). In the regression model, each unit of mean SDAI over time significantly increased the risk of RCL (HR 1.125, 95% CI 1.021-1.241;p = 0.018). Patients treated with biological had a lower risk of RCL than those treated with traditional DMARDs (HR 0.192, 95% CI 0.042-0.891;p = 0.035). In the 88 matched OA patients, the RCL rate was significantly lower than in the RA group (13.6%;p = 0.002).
Higher inflammatory DA increases the risk for radiographic loosening after THA/TKA in patients with RA. The significantly lower risk in patients with OA further underlines the potential role of inflammatory DA. In the context of treating RA to target, the presence of an arthroplasty might be considered as an indication for more stringent control of DA.