Foot deformities in rheumatoid arthritis and relevance of foot function index

The aim of this study were to assess what type of foot deformities are found in rheumatoid arthritis (RA) patients, to detect frequency of deformities, and to evaluate deformities affecting Foot Function Index (FFI) and patient functional capacity. Anteroposterior and lateral weight-bearing radiographs of 156 feet of 78 patients who had RA for ≥2 years and of 76 feet of 38 healthy controls were studied. We measured hallux valgus angle, intermetatarsal angle between first and second (M1/2) and intermetatarsal angle between first and fifth (M1/5) on anteroposterior radiographs, and calcaneal pitch on the lateral radiographs. We examined the feet of all RA patients and healthy controls for hallux rigidus, cock-up deformity, clawing toe, and mallet finger, and measured calcaneal valgus angle. FFI, comprised of pain, disability, and activity limitation subscales, was administered to all RA patients. Their Steinbrocker Functional Class (SFC) and Health Assessment Questionnaire (HAQ) scores were determined. We determined frequency of deformities as 96.2% in RA patients and 97.4% in controls by radiological and physical examination (p>0.05). The frequency of each deformity was markedly increased in RA patients, with the exception of calcaneal valgus deformity. There was significant correlation between SFC and HAQ with FFI and subscales (respectively, r=0.46, p=0.001; r=0.67, p=0.001). For FFI and subscales, HAQ was the most important predictor factor, followed by gender and hallux rigidus. Foot deformities are seen very frequently in RA. These deformities may affect patient functional foot, especially hallux rigidus and calcaneal valgus.