A patient-based questionnaire to assess outcomes of foot surgery: validation in the context of surgery for hallux valgus.

BACKGROUND: A patient-based outcome measure with good measurement properties is urgently needed for use in clinical trials of foot surgery. METHODS: We evaluated an existing foot pain and disability questionnaire (the Manchester Foot Pain and Disability Questionnaire) for its suitability as an outcome measure in the context of hallux valgus corrective surgery. Interviews with patients led to initial changes, resulting in 20 candidate questionnaire items with five response categories each. These were tested in a prospective study of 100 patients (representing 138 foot operations) undergoing hallux valgus corrective surgery. Analysis of underlying factor structure, dimensionality, internal reliability, construct validity and responsiveness of the questionnaire items in relation to (i) SF-36 general health survey and (ii) American Orthopaedic Foot and Ankle Society (AOFAS) hallux clinical scale resulted in a final 16 item questionnaire (the 'Manchester-Oxford Foot Questionnaire' (MOXFQ)), consisting of three domains/scales: 'Walking/standing' (seven items), 'Pain' (five items) and 'Social interaction' (four items) each having good measurement properties. All three domains were unidimensional. CONCLUSIONS: The new 16-item MOXFQ has good measurement properties in the context of outcomes assessment of surgery for hallux valgus. Future studies should assess the MOXFQ in the context of surgery for other foot and ankle conditions