Cross-Cultural Adaptation and Psychometric Validation of the Turkish Version of the American Orthopaedic Foot and Ankle Society Lesser Metatarsophalangeal-Interphalangeal Joint Scale

Abstract

Objective: Lesser toe disorders can cause significant functional impairment and pain, requiring reliable tools for outcome assessment. The American Orthopaedic Foot and Ankle Society (AOFAS) lesser metatarsophalangeal-interphalangeal (MTP-IP) joint scale is a clinician-based instrument frequently used in foot and ankle evaluations, yet no validated Turkish version exists. The aim of this study was to translate, culturally adapt, and evaluate the psychometric properties of the Turkish version of the AOFAS lesser MTP-IP scale. Methods: The scale was translated following international cross-cultural adaptation guidelines. A total of 43 patients with various lesser-toe pathologies were assessed using the AOFAS lesser MTP-IP, foot and ankle ability measure (FAAM), visual analogue scale, and short form-12 (SF-12). Test-retest reliability was assessed by calculating intraclass correlation coefficients [ICC (2,1)] using a two-way mixed-effects model with absolute agreement; by assessing internal consistency via Cronbach's alpha; and by evaluating agreement using Bland-Altman analysis. Construct validity was tested by correlating AOFAS scores with FAAM and SF-12 subscales. Floor and ceiling effects were also analyzed. Results: The Turkish version demonstrated excellent test-retest reliability [ICC (2,1)=0.96] and acceptable internal consistency (alpha=0.76). Bland-Altman plots revealed no systematic bias. Strong correlations were observed with FAAM-activities of daily living (r=0.93) and FAAM-sports (r=0.75), whereas correlations with SF-12 physical component summary (r=0.34) and MCS (r=0.45) were weak but significant, which is consistent with the hypothesized convergent and divergent validity. A notable ceiling effect was identified in the AOFAS function and alignment domains, consistent with the high functional status and low pain levels reported by participants. Conclusion: The Turkish adaptation ofthe AOFAS lesser MTP-IP scale is a reliable and valid instrumentfor evaluating pain, function, and alignment in patients with lesser toe disorders. Its strong psychometric performance supports its use in both clinical and research settings, although the observed ceiling effect should be interpreted in the context of patient characteristics.