The Functional and Structural Outcomes of Arthroscopic Iliopsoas Release

Background: Arthroscopic release of the iliopsoas tendon may alleviate pain associated with internal snapping hip, but previous reports of physical function, hip strength, and muscle atrophy after surgery are mixed. Hypothesis: The hips of patients who underwent arthroscopic iliopsoas release would demonstrate significantly reduced hip flexion strength and iliopsoas muscle volume when compared with their contralateral hips and the hips of patients who underwent hip arthroscopy without psoas release. Study Design: Cohort study; Level of evidence, 3. Methods: Eighteen patients who underwent hip arthroscopy with iliopsoas release for symptomatic internal snapping hip and concomitant femoroacetabular impingement (FAI) and/or chondrolabral damage (release group) and 18 patients who underwent arthroscopy for FAI and/or chondrolabral damage without iliopsoas release (control group) were evaluated at a mean of 21 months (range, 16-30 months) postoperatively. Magnetic resonance images were performed and segmented to calculate iliopsoas volume. Isometric hip flexion strength was evaluated in the supine and seated positions with a custom testing apparatus. Differences between groups and differences between the operative and nonoperative limbs within groups were compared with unpaired and paired t tests, respectively. Results: In the release group, the iliopsoas muscle of the surgical limb was significantly smaller (288 98 vs 384 +/- 113 cm(3), P < .001) and weaker in the seated position (13 +/- 4.7 vs 17 +/- 5.8 kg, P < .001) than the contralateral limb. Compared with the control group, the release group demonstrated a greater percentage decrease in iliopsoas volume on magnetic resonance imaging (-25% +/- 9.1% vs -0.6% +/- 4.6%, P < .001) and seated hip flexion strength (-19% +/- 16% vs -3.9% +/- 20%, P = .018) between the operative and contralateral limbs. There were no significant differences in supine strength between limbs or groups (all P > .168). Conclusion: Arthroscopic iliopsoas release results in iliopsoas atrophy with a 25% volume loss and a 19% reduction in seated hip flexion strength.