gms | German Medical Science

Objectives: Total joint arthroplasty (TJA) of the hip (THA) and knee (TKA) are well-established operations for end stage degenerative or inflammatory joint disease, and has excellent outcomes. In rheumatoid arthritis (RA) patients, it is performed in about 25%. Aseptic loosening (APL) is the most common complication after TJA. Reasons for aseptic loosening up to now are not fully understood. The most common theory is that the development of wear particles induces an inflammatory reaction which leads to local bone resorption, osteolysis and ultimately aseptic loosening. Systemic inflammation in RA might influence this process of local inflammatory-mediated osteolysis and could lead to higher aseptic loosening rates in RA patients, especially in those with increased inflammatory activity.

The objective is to assess the influence of rheumatoid arthritis (RA) disease activity on the risk of aseptic loosening after THA and TKA.

Methods: We identified RA patients who underwent THA/TKA and determined their disease activity levels using the simplified disease activity index (SDAI). The SDAI is a well-established composite score which is widely used in clinical trials as well as in clinical practice. The risk of aseptic loosening was estimated using radiographic signs of component loosening (RCL). These included radiolucent lines (RLL) with a width of >=2mm; osteolysis defined as nonlinear areas of endosteal, intracortical, or cancellous bone destruction exceeding 2mm in thickness; and migration of implant components of >=2mm. We performed Cox regression to estimate RCL based on SDAI, adjusting for the anti-rheumatic therapy (conventional vs. biological disease modifying drugs, DMARDs). We also investigated a cohort of OA patient, who were matched 2:1 for sex, age, date of surgery, and location of TJA as a control group without systemic inflammation and compared it with the RA group.

Results: 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 compared to those without (median; 25th and 75th percentile: 10.8; 8.6 and 15.8 vs 7.0; 2.7 and 15.5; p=0.043). In the Cox regression model, each unit of SDAI over time significantly increased the risk of RCL (HR 1.125, 95% CI 1.021-1.241; p=0.018). Patients treated with biologicals 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% vs 36.7%; p=0.002).

Conclusion: Higher RA disease activity increases the risk for aseptic loosening after THA or TKA. In OA, as a control disease without systemic inflammation, the risk is significantly lower. Orthopaedic surgeons and rheumatologists should be aware of the elevated risk when treating RA patients with TJA. In the context of treating RA to target, the presence of an arthroplasty should be considered as an indication for more stringent control of disease activity.