Class I Obesity Delays Achievement of Patient-Acceptable Symptom State but Not Minimum Clinically Important Difference or Substantial Clinical Benefit After Primary Hip Arthroscopy for Femoroacetabular Impingement Syndrome

Abstract

The aim of our study was to identify differences in the time taken to achieve the minimum clinically-important difference (MCID), substantial clinical benefit (SCB), and patient acceptable symptom state (PASS) following primary hip arthroscopy for treatment of femoroacetabular impingement syndrome (FAIS) among patients of different body mass index (BMI) categories. We conducted a retrospective comparative study of hip arthroscopy patients with minimum 2-year follow-up. BMI categories were defined as normal (18.5≤BMI<25.0), overweight (25.0≤ BMI<30.0), or class I obese (30.0≤BMI<35.0). All subjects completed the modified Harris Hip Score (mHHS) prior to surgery and at 6 months, 1 year, and 2 years postoperative. MCID and SCB cutoffs were defined as pre-to-postoperative increases in mHHS by ≥8.2 and ≥19.8, respectively. PASS cutoff was set at postoperative mHHS ≥74. Time to achievement of each milestone was compared using the interval-censored EMICM algorithm. The effect of BMI was adjusted for age and sex using an interval-censored proportional hazards model. 285 patients were included in the analysis: 150 (52.6%) normal BMI, 99 (34.7%) overweight, and 36 (12.6%) obese. Obese patients had lower mHHS at baseline (p=0.006) and at 2-year follow-up (p=0.008). There were no significant inter-group differences in time to achievement for MCID (p=0.92) or SCB (p=0.69), but obese patients had longer time to PASS than normal BMI patients (p=0.047). Multivariable analysis found obesity to be predictive of longer time to PASS (HR=0.55, p=0.007) but not MCID (HR=0.91, p=0.68) or SCB (HR=1.06, p=0.30). Class I obesity is associated with delays in achieving a literature-defined PASS threshold after primary hip arthroscopy for FAIS. However, future research should consider incorporating PASS anchor questions to determine whether obesity truly carries a risk of delayed achievement of a satisfactory state of health as it pertains to the hip.