Evaluation of the validity of the AOFAS clinical rating systems by correlation to the SF-36

This study evaluates the validity of the AOFAS Clinical Rating Systems by examining their level of correlation to the Medical Outcomes Study Short Form-36 (SF-36) in patients with foot and ankle complaints. The SF-36 is an extensively validated outcomes tool that has been used as a benchmark in examining the validity of outcomes instruments designed for the upper extremity, knee, shoulder, and general orthopaedic conditions. The study sample was 91 patients seen at the foot and ankle clinic of a university-based orthopaedic practice. Patients were administered both the AOFAS Clinical Rating Systems and SF-36 instruments. Pearson correlation coefficients of the AOFAS scores to the SF-36 sub-scales ranged from 0.02 to 0.36 in the overall study population. Correlation was higher for the sub-set of patients with ankle-hindfoot disorders (0.11 to 0.53) than patients with forefoot disorders (-0.05 to 0.25). The low levels of correlation seen in this study suggest poor construct validity of the AOFAS Clinical Rating Systems.