Minimal Clinically Important Difference for the FAAM-ADL Following Total Ankle Arthroplasty: Initial Estimates and Predictors of Achievement.

BACKGROUND

Total ankle arthroplasty (TAA) has emerged as a motion-preserving alternative to ankle arthrodesis for end-stage ankle osteoarthritis. As use increases, validated patient-reported outcome benchmarks are essential for interpreting functional recovery. The Foot and Ankle Ability Measure activities of daily living subscale (FAAM-ADL) is widely used in foot and ankle surgery; however, the minimal clinically important difference (MCID) following TAA has not been established. This study aimed to determine the MCID for the FAAM-ADL after primary TAA and to identify preliminary predictors of MCID achievement.

METHODS

One hundred sixty-four primary TAAs (1/2015-2/2022) at a single academic center (6 surgeons) with paired preoperative and ≥1-year postoperative FAAM-ADL scores were included. MCID was calculated using 3 established methods: the standard deviation (SD) approach, average change, and change difference methods. Diagnostic performance was evaluated using ROC analysis. Multivariable logistic regression assessed predictors of achieving MCID.

RESULTS

The mean age was 62.9 years, and 54.9% of patients were male. FAAM-ADL MCID thresholds varied by methodology, ranging from 12.5 points (SD method) to 26.0 (anchor 2, average change) to 32.3 points (anchor 2, change difference). The SD-derived threshold identified the greatest proportion of patients achieving MCID (73.2%), whereas the anchor 2 change difference method demonstrated the highest area under the curve (0.772) and positive predictive value (0.815). Postoperative FAAM-ADL improvement was significantly greater in satisfied vs dissatisfied patients across both anchors (P < .001). On multivariable analysis, lower preoperative FAAM-ADL was the only independent predictor of achieving MCID (OR 0.93, P < .001).

CONCLUSION

This study provides initial estimates of the first FAAM-ADL MCID thresholds following TAA of approximately 12.5 to 32.3 points. Baseline functional status was associated with MCID achievement, whereas demographic and comorbidity factors were not. These findings provide an initial benchmark for interpreting TAA outcomes and underscore the need for future prospective validation.

LEVEL OF EVIDENCE: Level III, retrospective cohort study.