Changes in muscle cross-sectional area and functional outcomes after hip arthroscopy for femoroacetabular impingement: A comparison between the operated and asymptomatic contralateral hip.

INTRODUCTION: The effect of hip arthroscopy on peri-hip muscle morphology in patients with femoroacetabular impingement syndrome (FAI) remains unclear. Understanding postoperative muscle recovery and its relationship with functional outcomes may help optimize rehabilitation strategies. This study aimed to evaluate preoperative and 1-year postoperative changes in peri-hip muscle cross-sectional areas (CSAs) on both the operated and asymptomatic contralateral sides in patients with FAI undergoing hip arthroscopy and to assess their association with functional outcomes. METHODS: This retrospective study included 66 patients who underwent hip arthroscopy for FAI, including femoroplasty, acetabuloplasty, labral repair, and complete capsular closure performed by a single surgeon. Axial T1-weighted pelvic magnetic resonance imaging scans obtained preoperatively and at 1-year postoperatively were analyzed. Bilateral CSAs of the gluteal, iliopsoas, iliocapsularis, quadriceps, and adductor muscle groups were measured. Functional outcomes were evaluated using the modified Harris Hip Score, Non-Arthritic Hip Score, Hip Outcome Score-Activities of Daily Living, Hip Outcome Score-Sports-Specific Subscale, Hip disability and Osteoarthritis Outcome Score, and Visual Analog Scale. RESULTS: At the 1-year follow-up, the gluteus maximus and rectus femoris CSAs on the operated side remained significantly smaller than those on the asymptomatic side. No significant postoperative increase in gluteus maximus CSA was observed, whereas the vastus medialis and rectus femoris demonstrated significant postoperative increases. Most other peri-hip muscles showed comparable pre- and postoperative CSAs between sides. All functional outcome scores improved significantly postoperatively, while Visual Analog Scale scores decreased. Postoperative gluteus maximus and iliocapsularis CSAs were positively correlated with postoperative modified Harris Hip Score values. CONCLUSIONS: Although most peri-hip muscle CSAs do not fully recover to asymptomatic side levels at 1 year following hip arthroscopy for FAI, improvements in specific muscle groups are associated with better functional outcomes. These findings underscore the importance of targeted postoperative rehabilitation focusing on key stabilizing muscles, particularly the gluteus maximus and iliocapsularis.