Thresholds for minimum clinically important difference, minimal important change and patient acceptable symptom state for the ACL-RSI and the K-SES in patients after anterior cruciate ligament reconstruction.

Abstract

Purpose: The aim of this study was to calculate and provide Patient Acceptable Symptom State (PASS) thresholds, Minimum Clinically Important Difference (MCID), and Minimal Important Change (MIC) values for the ACL-Return to Sport after Injury (ACL-RSI) scale and the Knee Self-Efficacy Scale (K-SES) in patients treated with ACL reconstruction.

Method: Data were extracted from a rehabilitation specific registry, Project ACL. The registry prospectively collects patient-reported outcomes (PROs). PASS, MCID and MIC were calculated using receiver operating characteristic (ROC) curve analysis and anchor-based methods. Calculations were made for patients who completed the ACL-RSI and K-SES₁₈ at follow-up points 4 (K-SES₁₈ only), 8, 12 and 18 months post-surgery.

Results: A total of 704 patients aged 15-50 year, who underwent ACL reconstruction were included. The PASS thresholds increased over time, with AUC values indicating acceptable discrimination at all follow-ups, especially at 18 months. The MCID values ranged from 1.6-4.1 for the K-SES₁₈ and 13.6-30.4 for the ACL-RSI. The MIC values varied between follow-ups, with negative or near-zero values observed at certain intervals, particularly for K-SES₁₈ future.

Conclusion: The PASS, MCID and MIC values for the K-SES₁₈ and the ACL-RSI vary over time. Practical thresholds are provided for clinicians to better interpret scores and to determine if meaningful improvements have been achieved.

Level of evidence: Level III.