A Modified Foot and Ankle Score for Assessing Patient Outcomes After First Metatarsophalangeal Arthrodesis.

First metatarsophalangeal (MTP) arthrodesis is commonly used to treat many end-stage first MTP diseases. The most widely used scale for measuring the clinical outcomes after this procedure, the American Orthopaedic Foot and Ankle Society Hallux Metatarsophalangeal-Interphalangeal scale, has not been adequately validated and does not measure specific foot functions. Another outcome measure, the patient-reported Foot and Ankle Outcome Score (FAOS) has acceptable construct validity but poor content validity. The FAOS scale has 42 questions, many of which are unrelated to the hallux. We designed a short-form FAOS (sf-FAOS) consisting of 11 questions that are more relevant to first MTP arthrodesis. The sf-FAOS includes a pain subscale and a function subscale, and the score of each subscale ranges from 0 (worst outcome) to 100 (best outcome). Our study has shown that the sf-FAOS scale has acceptable validity, reliability, and responsiveness. In 21 feet (16 patients) with hallux valgus after >1 year of follow-up, the mean sf-FAOS pain score had improved by 44.9 points after surgery (from 51.2 to 96.0; p < .001), and the mean sf-FAOS function score had improved by 22.5 points (from 47.3 to 69.8; p <.001). The improvement in the function score for running and jumping was limited.