Magnetic Resonance Imaging Comparison of Repaired versus Non-Repaired Hip Capsule in Patients Undergoing Hip Arthroscopy for Femoroacetabular Impingement: A Double-Blind, Randomized Controlled Trial

OBJECTIVES: Techniques used in hip arthroscopy continue to evolve and controversy surrounds the need for capsule repair following surgical intervention. The purposes of this study were to evaluate the magnetic resonance imaging (MRI) appearance of the hip capsule in patients with femoroacetabular impingement (FAI) undergoing hip arthroscopy with capsular repair versus non-repair. METHODS: A multicenter clinical trial was performed with 35 patients (50 hips) undergoing hip arthroscopy for treatment of FAI. Each hip was preoperatively randomized to capsular repair versus non-repair. MRI evaluation was performed by a radiologist at 6 and 24 weeks postoperatively. Patients and the radiologist were blinded to the randomization. Capsular defect size and the thickness of the capsule at the capsulotomy site and at locations both proximal and distal to the defect were recorded on each scan to determine their change over time. RESULTS: Compared to patients without capsular repair, those with capsular repair demonstrated significantly decreased mean capsular gapping at articular and muscular portions of the hip capsule at 6 weeks postoperatively (p < 0.001). This difference normalized between the two cohorts by 24 weeks postoperatively, with a significantly decreased mean capsular gapping at articular and muscular attachment sites of the hip capsule compared to 6 weeks postoperatively (p < 0.03). Defects were readily apparent on MRI imaging in regions where the capsule was not repaired. In contrast, irregular capsular thickening without a discrete defect was visible in most cases where the capsule was repaired at the time of arthroscopy. The appearance was variable after 24 weeks. The capsular defects that did close universally showed closure of the defect beginning at the muscular side of the capsule with bridging of capsular tissue then filling in on the articular side. CONCLUSION: Arthroscopic hip capsule repair results in significantly less capsule gapping at 6-week follow-up compared with non-repair, though the difference in gap size normalizes by 24-week follow-up.