The Minimal Clinically Important Difference of the American Orthopaedic Foot and Ankle Society Ankle Hindfoot Scale in Patients with Unstable Ankle Fracture.

BACKGROUD: The American Orthopaedic Foot and Ankle Society (AOFAS) Ankle Hindfoot Scale is frequently used as a patient-reported outcome measure (PROM) to evaluate recovery trajectories following foot and ankle injuries. This study aimed to determine the minimal clinically important difference (MCID) for the AOFAS score in patients with surgically treated unstable ankle fractures.

METHODS

Data were obtained from the ROutine versus on DEmand removal Of the syndesmotic stabilisation screw (RODEO) trial, a multicenter randomized controlled trial evaluating the management of syndesmotic screw fixation following ankle fracture surgery. Eligible patients completed the AOFAS scale at 3, 6, and 12 months postoperatively. The MCID was calculated using both anchor-based approaches (mean change, receiver operating characteristic [ROC] analysis) and distribution-based approaches (minimal detectable change [MDC] and 0.5 standard deviation).

RESULTS

A total of 148 patients were included, with a mean age of 47 years, and a male predominance of 63.5%. Median AOFAS scores improved significantly over time, rising from 73.0 at 3 months to 85.0 at 12 months postoperatively (p < 0.001). The MCID for the anchor-based mean change method was calculated to be 7.1 for the 3- to 6-month interval and 7.8 for the 6- to 12-month interval. ROC curve analysis indicated MCID values of 0.5 and 5.5 for these intervals, respectively. Distribution-based MCIDs were 9.2 at 3 months, 8.2 at 6 months, and 7.1 at 12 months. The MDC was 3.5 at 3 months, 2.8 at 6 months, and 4.1 at 12 months.

CONCLUSIONS

Despite the extended recovery period, often up to 12 months, following surgical stabilization of unstable ankle fractures with syndesmotic injury, the AOFAS remains one of the most utilized PROMs in this context. Based on these findings, a change in score between 4.1 and 7.8 points should be considered clinically relevant at the 1-year follow-up.