Determining Clinically Meaningful Thresholds for the Non-Arthritic Hip Score in Patients Undergoing Arthroscopy for Femoroacetabular Impingement Syndrome.

Abstract

PURPOSE\ns: To improve interpretability of the Nonarthritic Hip Score (NAHS) by determining the minimal clinically important difference (MCID), patient acceptable symptomatic state (PASS), and substantial clinical benefit (SCB) after hip arthroscopy for femoroacetabular impingement (FAI). The secondary aim was to identify variables associated with achievement of the thresholds.\n\n\nMETHODS\nPatients who underwent hip arthroscopy for FAI and completed postoperative questionnaires between August 2019 and March 2020 were included. Patients were excluded if they had a previous ipsilateral hip surgery, a gluteus medius repair, or a previous hip condition. The MCID, PASS, and SCB thresholds were calculated for NAHS at minimum one-, two-, and five-year follow-up. Distribution and anchor-based methods using receiver operating characteristic analysis were utilized to determine the thresholds. Multivariate logistic regression was performed to determine predictors of achieving MCID and PASS.\n\n\nRESULTS\nThe study included 343 hips with an average follow-up of 48 months. Based on the distribution-based approach, the MCID was 8.7 using the 0.5 standard deviation (SD) of baseline scores method. Using the 0.5 SD of score change method resulted in MCID scores of 9.1, 8.3, and 12.6 at minimum one-, two-, and five-years, respectively. PASS thresholds for the previously stated timepoints were 81.9, 85.6, and 81.9. The SCB absolute thresholds were 91.9, 94.4, and 93.1, and the score change thresholds were 30.6, 24.4, and 29.3, for minimum one-, two-, and five-years, respectively. Preoperative NAHS was positively associated with achievement of PASS and inversely related to achievement of MCID.\n\n\nCONCLUSION\nThis study provides important clinical thresholds for the NAHS. These thresholds were determined for minimum one-, two-, and five-year timepoints. The MCID was determined as 8.7, PASS ranged between 81.9-85.6, and absolute SCB ranged from 91.9-94.4. Preoperative NAHS was found to be positively associated with achievement of PASS and inversely related to achievement of MCID.