Abstract and Introduction
Abstract
Objectives: To determine whether the introduction of biological DMARDs (bDMARDs) was associated with reduced incidences of total hip and knee arthroplasty (THA/TKA) among patients with RA compared with OA.
Methods: Using a population-based cohort in British Columbia, Canada, RA and OA patients diagnosed between 1995 and 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 total joint arthroplasty 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 with +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 incidences 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.
Introduction
RA, the most common inflammatory arthritis, affects ~1.2% of Canadians aged 16 years and older.[1] Uncontrolled inflammation causes irreversible joint damage that sometimes requires total joint arthroplasty (TJA).[2] Overall, TJA is effective at reducing pain and improving function, but is expensive, and complications can occur especially in RA,[3] sometimes necessitating revision surgery.[4–6]
Biological DMARDs (bDMARDs), such as TNF-α inhibitors, are very effective at suppressing inflammation and can halt the progression of RA, preventing joint damage.[7–9] bDMARDs, including anti-TNF-α agents, were first introduced to Canada in the early 2000s. By 2002, three major anti-TNF-α bDMARDs, etanercept, infliximab and adalimumab, became available for the treatment of RA.[10] Given the effectiveness of bDMARDs, it would seem reasonable to expect that they would reduce the need for TJA. However, evidence is conflicting. Some studies have demonstrated benefits of bDMARDs,[11–18] while others have shown no effect or even increased numbers of TJAs.[11,12,17,19,20]
In research assessing the potential impact of bDMARDs on TJA rates, it is important to control for changes in TJA availability over time. OA is another condition for which TJA is often required, and for which bDMARDs are not used as they have shown no or minimum benefits on pain, synovitis or bone marrow lesions.[21–24] This makes OA an ideal comparator group that has not been utilized in previous studies. The purpose of this study is to examine the longitudinal impact of the introduction of bDMARDs on total hip and knee replacements in a population-based cohort in British Columbia (BC), Canada, using an innovative quasi-experimental study design that uses OA as a comparator group to RA.
Rheumatology. 2022;61(5):1819-1830. © 2022 Oxford University Press
