Volume of Gluteus Maximus and Minimus Increases After Hip Arthroscopy for femoroacatabular impingement syndrome

ABSTRACT Purpose The purpose of this study was to investigate the change in muscle volume around the hip in patients with femoro-acetabular impingement (FAI) after arthroscopy and evaluate other factors related to muscle change. Methods We performed a retrospective review of magnetic resonance imaging (MRI) data of FAI patients who underwent hip arthroscopy. MRI was obtained preoperatively and postoperatively. The cross-sectional area (CSA) of muscles were determined on axial images. Wilcoxon signed-rank test was used to determine the differences between preoperative and postoperative hip muscle CSA. The correlations of change in muscle CSA with age, gender, BMI, pain level, preoperative symptom duration, follow-up time and multiple validated patient-reported outcomes were also analyzed with a spearman rank correlation test. Results 51 patients with a mean age of 36.5±5.6 years were included and analyzed. The follow-up was 26.6±0.5 months(range24-40m), and 27(52.9%) were female. Patients with FAI showed increased hip muscle CSA of gluteus maximus (P=0.002), gluteus minimus (P=0.001) at the postoperation compared with preoperation, the value for the change in medius CSA was underpowered, no differences in other hip muscle CSA were observed. The increased muscle CSA of gluteus maximus was significantly correlated with the improvement of mHHS (ρ=0.404, P=0.003). The increased muscle CSA of gluteus minimus was significantly correlated with the improvement of VAS pain (ρ=0.452, P=0.001). Age, BMI, gender, symptom duration, follow-up time were not significantly correlated with change in muscle CSA. Conclusion Patients with FAI have a significantly increased post-operative muscle CSA of the gluteus maximus (7.8%) and the gluteus minimus (11.6%) compared with pre-operative values. The increased muscle CSA of the gluteus maximus and gluteus minimus was significantly correlated with improvement in mHHS and VAS pain, respectively. The increase of muscle volume may be associated with the improvement of subjective function and pain relief.