SAT0605 TRENDS OF TOTAL JOINT ARTHROPLASTY AMONG PATIENTS WITH OSTEOARTHRITIS, RHEUMATOID ARTHRITIS AND ANKYLOSING SPONDYLITIS IN BRITISH COLUMBIA, CANADA, 1998-2013

Background: Total joint replacement or arthroplasty (TJA) is an expensive surgical treatment for severe arthritis when other treatments have failed. Given the substantial changes in the available treatments over the past 2 decades, it is of interest to describe the trends in the use of TJA among patients with different types of arthritis in the general population. Objectives: The aim of this study was to examine longitudinal trends of TJA including total hip, knee and shoulder replacement performed in British Columbia, Canada, between the year of 1998 and 2013 due to three different types of arthritis conditions: 1) Osteoarthritis (OA), 2) Rheumatoid arthritis (RA) and 3) Ankylosing spondylitis (AS). Methods: We analyzed large, population-based administrative data obtained from Population Data BC that includes patients aged 20+ in B.C., Canada, linked to diagnostic codes of hospitalizations and physician visits. Using the Canadian Classification of Diagnostic, Therapeutic and Surgical Procedures (CCP) procedure codes and the Canadian Classification of Health Intervention (CCI) procedure codes, we identified total joint arthroplasty procedures (TJA) including total hip arthroplasty (THA), total knee arthroplasty (TKA) and total shoulder arthroplasty (TSA) performed among OA, RA and AS prevalent cases. We calculated annual rates of THA, TKA and TSA performed among OA, RA and AS patients. We divided the study period into four equal-length periods and calculated period prevalence rates of THA, TKA and TSA per 100,000 person years as the ratio of the number of cases per period (numerator) to the total follow up time within the same period (denominator). We performed trend tests to test if there are changes in these rates over time. Results: For OA and RA, TKA was the most common types of TJA performed, while THA remained to be the most common types of TJA performed among AS patients. For OA, period prevalence rate of THA, TKA and TSA increased during the study period (Table 1.). For RA patients, THA and TKA rates showed a decreasing trend. For AS patients, THA rates decreased and TSA increased. For RA and AS, TSA rates did not show a significant trend. Among patients with OA, annual TJA rates per 100,000 persons show an overall increasing trend. The TJA rates remained relatively flat from 1998 to 2003, started to increase and peaked in 2006, and declined slightly thereafter (Figure 1.). Among patients with inflammatory arthritis (RA and AS), annual TJA rates decreased over the study period (Figure 1.). Annual proportion of TJA perfromed due to inflammatory arthritides significantly decreased from 1998 to 2013 (4.3% versus 1.0%) (Figure 2.). Conclusion: There have been important changes in the annual rate of total joint replacement in B.C., Canada, during the study period from 1998 to 2013. TJA use increased in OA patients but decreased in patients with inflammatory arthritis (RA and AS). Effective treatment for inflammatory arthritis, such as TNF-α inhibitors introduced in British Columbia in 2001-2002, may have effectively reduced the need for arthroplasty in RA and AS. Acknowledgments: This study was supported by CIHR (team grant THC-135235), and NSERC (RGPIN-2018-04313). Disclosure of Interests: None declared