Background The disease course of patients with rheumatoid arthritis has become milder in recent years,(1, 2) and the change in treatment mainly represented by methotrexate from the late 1970ties is believed to be a major contributor to this,(3) although it has been argued that the improved outcome is partly a secular trend.(4) Joint replacement surgery can be considered an objective proxy for a destructed joint, and studying its change in incidence over time gives valuable information regarding the prognosis of patients with rheumatoid arthritis.
Objectives We wished to investigate the incidence of joint replacement surgery in patients with rheumatoid arthritis and relate the change over time to the change in use of disease modifying anti rheumatic drugs (DMARDs).
Methods From the Norwegian Arthroplasty Register we selected arthroplasties of the hip, knee, ankle, toe, shoulder, elbow, wrist, carpus and fingers in patients with rheumatoid arthritis in the years 1994-2012 (n=11337, 82% women), and using Poisson regression we analysed the time trend in the incidence of procedures being performed. Analyses were performed for each joint, joints grouped together and for different age categories. For the communal analysis operations in patients with osteoarthritis were included for comparison. We also collected data from the Norwegian Prescription Database established in 2004 to analyse changes in the number of individuals using methotrexate, leflunomide, sulfasalazine or hydroxychloroquine, and any change in mean weekly per oral methotrexate dose.
Results We found a significant decrease in the incidence of arthroplasty surgery in patients with rheumatoid arthritis (coefficient of -0.050 per year, p<0.001) as opposed to a significant increase in patients with osteoarthritis (coefficient of 0.047 per year, p<0.001). The decrease was most prominent in the age groups 50-59 years, 60-69 years and 70-79 years, and finger joint prostheses had the greatest reduction with an incidence of 0.5 per 100 000 in 2012 compared with 7.49 per 100 000 in 1994. From 2004 to 2012 the use of methotrexate increased steadily from 0.030 to 0.056 users per 100 000 inhabitants, and mean dose increased from 10.8 to 12.1 mg per week. Only small changes were seen for the other DMARDs
Conclusions The reduction in rheumatic surgery reported by other authors (5, 6) was confirmed in this large material from the Norwegian Arthroplasty Register, and the trend seen in earlier time periods continued into the biologic era and throughout the study period 1994-2012. In addition to the introduction of TNF-α inhibitors in 1998, the use of methotrexate increased in all available years from 2004-2012, thus coinciding with the reduction in prosthesis surgery and the improved prognosis of patients with rheumatoid arthritis.
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Disclosure of Interest None declared