Has the incidence of total joint arthroplasty in rheumatoid arthritis decreased in the era of biologics use? A population-based cohort study.

OBJECTIVES To determine whether the introduction of biological disease-modifying anti-rheumatic drugs (bDMARDs) was associated with reduced incidences of total hip and knee arthroplasty (THA/TKA) among patients with rheumatoid arthritis (RA) compared with osteoarthritis (OA). METHODS Using a population-based cohort in British Columbia, Canada, RA and OA patients diagnosed between 1995-2007 were divided into semi-annual cohorts according to diagnosis date. For each cohort, we calculated 8-year incidence rates of THA and TKA. We compared levels and trends of THA/TKA incidence in RA/OA patients diagnosed during pre-bDMARDs (1995-2001) and post-bDMARDs (2003-2007) periods using interrupted time-series analysis, adjusting for baseline characteristics. Adjusted 8-year TJA incidence estimated for RA/OA cohorts diagnosed five years after bDMARDs introduction were compared with expected rates assuming no bDMARDs introduction, based on extrapolation of pre-bDMARDs trends. RESULTS We identified 60,227 RA and 288,260 OA incident cases. For cohorts diagnosed pre-bDMARDs, 8-year THA/TKA incidence rates increased over time in both RA and OA. For cohorts diagnosed post-bDMARDs, these rates decreased over time in RA but continued to increase for OA. For RA, differences between the post- and pre-bDMARDs secular trends in incidence rates were -0.49 (p = 0.002) for THA and -0.36 (p = 0.003) for TKA, compared to + 0.40 (p = 0.006) and +0.54 (p < 0.001), respectively, for OA. For RA cohorts diagnosed five years after bDMARDs introduction, 8-year incidence were 26.9% and 12.6% lower for THA and TKA, respectively, than expected rates. In contrast, corresponding rates in OA were higher by 11.7% and 16.6%, respectively. CONCLUSION Arthritis onset after bDMARDs introduction is associated with a significant reduction in THA/TKA incidence in RA, but not in OA. The reduction reflects a significant improvement in RA treatment during the biological era.