The Impact of Hindfoot Deformity on Disability of Korean Patients with Rheumatoid Arthritis

Abstract

Background/Purpose: Rheumatoid arthritis (RA) commonly involves the hindfoot, but this part is frequently overlooked when caring for patients with multiple joints pain and deformity. For example, disease activity score (DAS)-28 is most widely used assessment tool of disease activity, but the joints in the feet including hind foot are not included in the 28 joint count. Functional disability has been identified as a core outcome measure in RA and it is affected by various factors. However, until now, there have been few studies performed to assess the impact of hindfoot deformity on the functional disability of RA patients. This study aims to evaluate the impact of hindfoot deformities on the functional disability of RA patients. Methods: In this cross-sectional study, we evaluated about foot deformities using AP and lateral views of simple radiography. The deformities of feet were divided into three parts: the hindfoot, midfoot, and forefoot deformity. We compared the clinical features including HAQ score of RA patients according to the presence of hindfoot deformity, and then performed univariate and multivariable logistic analyses to find the impact of hindfoot deformities on functional disability. Results: A total of 120 patients (113 females, 7 males) with a mean age of 46.9 years were included in this study. The prevalences of hindfoot, midfoot and forefoot deformities were 33 (27.5%), 41 (34.2%) and 49 (40.8%), respectively. Patients who had hindfoot deformity showed longer disease duration, higher disease activity, higher functional disability, and commonly prescribed with biologic DMARDs comopared with patients without hindfoot deformity. In the univariate analysis, hindfoot deformity showed 4.2 fold increased risk of higher functional disability group (HAQ score ≥ 0.5 as a median). After adjusting age, disease duration, disease activity, biologic DMARD use, and other feet deformities, hindfoot deformity showed high odds ratio (OR) but not statistically significant (OR 2.6, 95% CI 0.77-8.57). Conclusion: The hindfoot deformities might be associated with functional disability of RA patients. Further study with large sample size will be helpful to identify the impact of hindfoot deformity on the functional disability of RA patients.