The foot function index is more sensitive to change than the Leeds Foot Impact Scale for evaluating rheumatoid arthritis patients after forefoot or hindfoot reconstruction

Abstract

Purpose: This study examines the responsiveness of the Foot Functional Index (FFI) and Leeds Foot Impact Scale for Rheumatoid Arthritis (LFIS-RA) in rheumatoid arthritis (RA) patients receiving a forefoot or hindfoot reconstruction. Methods: This was a prospective cohort study including 30 rheumatoid arthritis patients with severe rheumatoid foot deformities in need for surgical correction. Responsiveness was measured using distribution-based methods (standardized effect size, standardized response mean and Guyatt responsiveness ratio) and anchor-based methods (receiver operating characteristics curves and correlation analyses) by making use of an anchor question. To examine the depth of the questionnaires we measured the floor and ceiling effects. Results: The study population consisted of three males and 27 females, with a mean age of 62 years. The mean follow-up time was 38 months. Twenty-two feet received a forefoot reconstruction and eight feet a triple arthrodesis. For the FFI the SES was −0.80, SRM was −0.85 and the GRR was −1.25. For the LFIS-RA the SES was 0.58, SRM was 0.58 and the GRR was 0.88. The AUC was 0.741 and 0.645 for FFI and LFIS, respectively. Contrary to the LFIS-RA, the FFI showed a significant correlation between change score and the anchor question. Both questionnaires did not show a significant floor or ceiling effect. Conclusion: The FFI showed a large responsiveness and the LFIS- RA showed moderate responsiveness in rheumatoid arthritis patients receiving forefoot or hindfoot surgery, without floor or ceiling effects in both questionnaires.