Minimally important change was estimated for the Manchester–Oxford Foot Questionnaire after foot/ankle surgery

Abstract

ObjectivesTo ascertain the smallest amounts of change for the three Manchester–Oxford Foot Questionnaire (MOXFQ) domains that are likely to be clinically meaningful and beyond measurement error for conditions affecting the foot/ankle. Estimates were compared with those from the Short-Form 36 (SF-36). Study Design and SettingA prospective observational study of 671 consecutive patients undergoing foot or ankle surgery at an orthopedic hospital. Before and 9 months after surgery, patients completed the MOXFQ and SF-36; transition items (anchor) asked about perceived changes in foot/ankle pain or problems since the surgery. ResultsFour hundred ninety-one patients completed pre- and postoperative questionnaires. Anchor-based minimal clinically important change (MCIC) values were ∼13 points for each of the MOXFQ Walking/standing (W/S), Pain, and Social Interaction (S-I) domains [and greater than the standard error of measurement (SEM)]. MCIC values for all SF-36 domains fell within the SEM. Between-group MCIDs for the MOXFQ were W/S, 16.2; Pain, 9.9; S-I, 9.3. Distribution-based minimal detectable change (MDC90) values for the MOXFQ were ∼11, ∼12, and ∼16 score points for the W/S, Pain, and S-I scales, respectively. ConclusionThis article provides information for aiding the interpretability of MOXFQ outcomes data and for planning future studies. The SF-36 is not recommended as a primary outcome for foot/ankle surgery.