Estimation of the Minimal Important Difference and Validation of Foot and Ankle Instruments

Patients who are waiting for foot and ankle surgery are recruited from four large referral centers (Peijas Hospital, Seinäjoki Central Hospital, Central Finland Central Hospital, Oulu University Hospital). Participants fill in foot and ankle-specific, generic and sosiodemographic questionnaires on the day of surgery, 6 months after surgery, and 6 months 2 weeks after surgery. Both pen-and-paper and electronic options for completing the questionnaire set are provided. The data obtained from the Foot and ankle outcome score (FAOS), European foot and ankle society (EFAS) score, modified Lower extremity functional scale (LEFS), Visual analog scale foot and ankle (VAS-FA), Manchester Oxford foot and ankle (MOxFA) questionnaire, and the Foot and ankle ability measure (FAAM) are analyzed using the Rasch Measurement Theory and several other psychometric approaches to investigate minimal important change, reliability, responsiveness and validity of foot and ankle PRO instruments.