Defining the Minimal Clinically Important Difference in Athletes Undergoing Arthroscopic Correction of Sports-Related Femoroacetabular Impingement: The Percentage of Possible Improvement

Abstract

Background: Measures of clinically meaningful improvement in patient-reported outcomes within orthopaedics are becoming a minimum requirement to establish the success of an intervention. Purpose: To (1) define the minimal clinically important difference (MCID) at 2 years postoperatively in competitive athletes undergoing hip arthroscopic surgery for symptomatic, sports-related femoroacetabular impingement utilizing existing anchor- and distribution-based methods and (2) derive a measure of the MCID using the percentage of possible improvement (POPI) method and compare against existing techniques. Study Design: Cohort study (diagnosis); Level of evidence, 2. Methods: There were 2 objective outcome measures—the modified Harris Hip Score (mHHS) and 36-Item Short Form Health Survey (SF-36)—administered at baseline and 2 years postoperatively. External anchor questions were used to determine the MCID through mean change, mean difference, and receiver operating characteristic (ROC) techniques. Distribution-based calculations consisted of 0.5 SD, effect size, and standard error of measurement techniques. The POPI was calculated alongside each technique as an achieved percentage change of maximum available improvement for each athlete relative to the individual baseline score. The impact of the preoperative baseline score on the MCID was assessed by assigning athletes to groups determined by baseline percentiles. Statistical analysis was performed, with P