Background Distal interphalangeal (DIP) joint osteoarthritis (OA) is a disorder associated with female sex and age and is considered as unrelated to rheumatoid arthritis (RA). The long term radiologic course of DIP OA in patients with RA is unknown.
Objectives To investigate the prevalence and demographic characteristics of DIP OA progression in RA patients.
Methods RA patients of the Swiss Clinical Quality Management in Rheumatic Diseases (SCQM) cohort, who had at least two subsequent hand radiographies taken between November 1983 and October 2014 were analysed. DIP joints (II-V) were scored for the radiologic presence and severity of osteophytes, subchondral sclerosis, joint space narrowing and erosions according to the modified Kellgren Lawrence Score (KLS).
Results 2890 (35%) patients out of 8280 of the SCQM RA cohort fulfilled the inclusion criteria. Their mean age was 57.5 years (standard deviation (SD) 10.5), 76% were female, 78% were rheumatoid factor positive and 69% were ACPA positive. At baseline, the mean disease duration was 9.7 years (SD 8.5). The mean follow-up between the first and last radiography was 5.4 years (SD 3.2). Baseline radiographies showed osteophytes in 21% of 21,333 DIP joints, joint space narrowing in 13%, osteosclerosis in 9% and erosions in 1%. The KLS was 1 in 13% of DIP joints, 2 in 22%, 3 in 4% and 4 in 2% at baseline radiographies. The KLS increased in 12% of DIP joints during the radiologic follow-up, decreased in 2% and remained stable in 86% of DIP joints. Female sex (p<0.001), age>55 years (p=0.005) and a negative rheumatoid factor (p=0.049) were associated with OA progression.
Conclusions Known risk factors for DIP OA were also associated with its radiologic progression in RA patients. Radiologic progression and erosions in DIP OA are low in this cohort, potentially due to RA treatment.
Disclosure of Interest None declared