To investigate foot deformities in rheumatoid arthritis (RA) in relation to the disease severity.
Radiographs of 100 weight bearing feet of 50 patients who had had RA for >10 years (mean 13.5 years) were studied. The patients were classified into 2 study groups according to the severity of disease. We measured hallux valgus angle (HVA), intermetatarsal angle between first and 2nd (M1/2), and intermetatarsal angle between first and 5th (M1/5) on anteroposterior (AP) radiographs, as well as calcaneal pitch (CP) and first metatarsal pitch (MP) on lateral radiographs. The differences in these angles between the 2 groups (Inter-group study) and the correlations among angles within each group (Intra-group study) were examined.
Inter-group study showed significant differences between the 2 groups for all variables. Intra-group study, on the other hand, showed no correlation between variables of the 2 deformities, i.e., splaying of forefoot (M1/2 and M1/5) and flattening of longitudinal arch (CP and MP). Only HVA correlated with the splaying (M1/2 and M1/5) in both study groups.
Disease severity is related to the progression of foot deformities in RA, but the flattening and the splaying are not correlated with each other. We believe that foot deformities should be treated properly and early, especially for patients who are expected to have severe disease.