New Insight into the Effects of Different Types of Midfoot and Hindfoot Deformities on the Functional Outcomes of Rheumatoid Arthritis Patients

In advanced stages of rheumatoid arthritis (RA), the pattern of joint involvement leads to varied types of foot deformities such as forefoot, midfoot, and hindfoot deformities. We aim to evaluate midfoot and hindfoot deformities and their effect on functional outcomes in RA patients. In this prospective cross-sectional study clinical and radiological evaluations of 100 adult RA patients were studied for midfoot and hindfoot deformities. The RA disease activity, functional disability level, specific foot and ankle assessments, gait speed, and balance tests were assessed. Radiological examinations of the weight-bearing feet in a standing position were done. We found that the most frequent deformity type was the planovalgus foot (24%). There were statistically significant differences between the types of foot deformities and disease duration, disease activity, falls, Tinetti and Berg balance Test, and health assessment questionnaire-disability index. The multivariate regression analysis of independent correlates of falling detected that patients with equinovarus deformity were 2.5 times more liable for falling with 63.5% predictive power. According to the predictive criteria of deformity type for falling, the equinocavovarus type had accuracy, sensitivity, specificity, positive predictive value, and negative predictive value of 91%, 84.5%, 98.5%, 99%, and 84%, respectively. We found in RA patients, midfoot and hindfoot deformities cause a significant reduction of functional ability and quality of life. The early detection of foot deformities requires a good awareness of the clinical and radiographic diagnosis of different types of deformities thus reducing the possible functional disabilities via early management by combined orthotic, physiotherapy, and surgical treatments.