Design and psychometric testing of a new patient-reported outcome measure for ankle treatment.

BACKGROUND

Several outcome scores are used to assess the outcome of ankle surgery, but many are not validated and there is currently no 'gold-standard'. Consequently, there is demand to develop a new 'gold-standard' score to assess ankle surgery. The study aim was to review existing scores to develop and validate a new patient-reported outcome measure (PROM) to assess the outcome of operative ankle surgery.

METHODS

The questionnaire items covered three areas: pain, symptoms and activity. The scale was reviewed by a patient group, resulting in the Oswestry Ankle score (Os-Ankle). The Os-Ankle was validated using a cohort of 206 patients at both pre-operative and post-operative stages of ankle surgery. Patients provided two other outcome scores, the scores currently used at our centre: the Manchester-Oxford Foot Questionnaire (MOxFQ) and the Veterans Rand-12 (VR-12). Factor analysis and Rasch were determined to assess the psychometric testing and design of the Os-Ankle score. A follow up paper assesses the validity of the Os-Ankle against two existing scores.

RESULTS

Results of the factor and Rasch analysis suggested that 12-items should be removed. The remaining 18-items fitted the Rasch model well, suggesting good internal consistency.

CONCLUSION

A new ankle PROM, the Os-Ankle, was successfully developed and demonstrated good psychometric testing. The Os-Ankle evaluates pain, symptoms and activities and results in a single score. The Os-Ankle has been validated in our follow up paper, and is ready to be implemented by ankle clinicians to monitor clinical outcomes. With the publication of two back to back papers, it will allow for further engage with other clinicians and other centres.

LEVEL OF EVIDENCE: Level II, prospective comparative study.