Quantifying the Minimal Clinically Important Difference of the Self-Administered Foot Evaluation Questionnaire (SAFE-Q) in Patients Undergoing Surgery for Ankle Osteoarthritis.

Abstract

The Self-Administered Foot Evaluation Questionnaire (SAFE-Q) is a validated foot- and ankle-specific patient-reported outcome measure. However, minimal clinically important difference (MCID) values have not been established for SAFE-Q after surgery for ankle osteoarthritis. To determine anchor-based and distribution-based MCIDs for SAFE-Q subscales in patients undergoing surgery for ankle osteoarthritis. Retrospective cohort study. We analyzed 88 patients with ankle osteoarthritis undergoing surgery who completed SAFE-Q preoperatively and ≥12 months postoperatively. The SAFE-Q subscales included pain and pain-related (PP), physical function and daily living (PF), social function (SF), shoe-related problems (SH), and general health and well-being (GH). Anchor-based MCIDs were derived using receiver operating characteristic (ROC) curves, with patient satisfaction as the external anchor. Distribution-based MCIDs were estimated using one-half standard deviation of baseline scores. SAFE-Q scores improved significantly across all domains. Eighty patients (91%) reported satisfaction. Anchor-based MCIDs were +13.9 for PP and +9.1 for PF, with acceptable discriminative accuracy (area under the ROC curve 0.759 and 0.743, respectively). In contrast, GH was affected by ceiling effects, and SF and SH showed limited discriminative ability. Distribution-based MCIDs ranged from 9-13 points and closely matched anchor-based values for PP and PF. This study provides the first MCID estimates for SAFE-Q in ankle osteoarthritis surgery. PP and PF demonstrated clinically meaningful MCIDs of approximately 9-14 points, indicating that these subscales are most appropriate for assessing meaningful postoperative improvement. These thresholds offer practical guidance for clinical interpretation and future trial design. 3, retrospective cohort study.