Increased cross-sectional area of the gluteus maximus after hip arthroscopy for femoroacetabular impingement correlates with patient-reported outcomes

Abstract

Introduction:

The purpose of this study was to conduct an analysis of the cross-sectional area (CSA) of hip musculature before and after hip arthroscopy (HA) for femoroacetabular impingement (FAI). The hypothesis was that there will be a significant increase in the CSA of analysed hip muscles that will correlate with increases in PROs following surgery.

Methods:

This is a single-centre, single-surgeon, retrospective analysis performed between August 2011 and February 2022. All hips that had a preoperative MRI within 1 year of their date of surgery and ≥1 postoperative MRI >2 months after surgery were included. Cross-sectional areas of the gluteus maximus, gluteus medius, gluteus minimus, iliopsoas, pectineus, sartorius, rectus femoris and tensor fascia lata muscles were measured by 1 blinded researcher and results were checked for reliability by a musculoskeletal radiologist. Normally distributed continuous variables between cohorts were compared using the independent samples t-test.

Results:

89 hips met criteria to be included in the analysis. The cohort had an average age of 35.8 ± 15.7 years, was 66.3% female, and had an average BMI of 23.3 ± 8.1 kg/m². The mean time between surgery and postoperative MRI was 14.8 ± 8.3 months. There was a significant difference between preoperative and postoperative hip muscle CSA for gluteus maximus (4298.6 ± 883.6 mm² vs. 4384.6 ± 967.6 mm², p < 0.01) and gluteus minimus (1037.0 ± 199.2 mm² vs. 1074.9 ± 202.3 mm², p < 0.001). A linear regression found that an increase in the change in CSA of the gluteus maximus (β = 3.237, p = 0.037) significantly predicted an increase in mHHS at 1 year when controlling for time between surgery and post-op MRI.

Conclusions:

Gluteus maximus and minimus muscles demonstrated significantly increased CSA after HA for FAI patients. Change in CSA was positively correlated with PROs for the gluteus maximus at 1-year follow-up. These findings underscore the clinical significance of muscle adaptations following hip arthroscopy for FAI.