Preserved Daily Function Despite Significant Muscle Atrophy and Strength Deficits: A Matched-Cohort Study of Iliopsoas Release for Ischiofemoral Impingement.

OBJECTIVE: The arthroscopic management of concomitant ischiofemoral impingement (IFI) and femoroacetabular impingement (FAI) frequently necessitates iliopsoas release; however, concerns regarding potential iatrogenic muscle atrophy and strength deficits remain unresolved. Therefore, the purpose of this study was to evaluate the clinical outcomes, volumetric changes, muscle morphology, and objective isokinetic muscle strength in patients undergoing arthroscopic treatment for concomitant IFI and FAI involving iliopsoas release.

METHODS: This retrospective matched-cohort study analyzed patients treated between January 2019 and January 2020. It included 15 female patients (IFI + FAI group) who underwent arthroscopic IFI decompression and iliopsoas release, and 15 propensity-matched patients (Isolated FAI group) treated for FAI alone. At a minimum 2-year follow-up, patient-reported outcomes (PROs) were assessed. Muscle morphology was evaluated on MRI using 3D volumetric reconstruction for muscle volume, and the Goutallier classification was used to assess fatty infiltration at three standardized anatomical levels. Functional recovery was objectively measured using isokinetic hip flexor and extensor strength testing at 60°/s and 180°/s, comparing the involved hip to the uninvolved contralateral side. Statistical analyses included paired t-tests, Mann-Whitney U tests, and Wilcoxon signed-rank tests.

RESULTS: Both groups demonstrated significant improvements in PROs postoperatively (p < 0.001). Volumetric analysis revealed a significant reduction in iliopsoas muscle volume (25.5% decrease) in the IFI + FAI group postoperatively. Despite this volumetric reduction, postoperative MRI demonstrated preservation of muscle quality, as evidenced by low Goutallier grades (Grade < 1) and no significant difference in fatty infiltration compared to the control group (p > 0.05). Functionally, isokinetic testing demonstrated significant deficits in peak flexion torque compared to the healthy contralateral side (p < 0.001). Notably, while outcomes for activities of daily living were satisfactory, a statistically significant difference was observed in the Substantial Clinical Benefit (SCB) achievement rate regarding sports function between the groups.

CONCLUSION: Iliopsoas release resulted in significant strength deficits, but no significant changes in muscle morphology were observed. However, patient-reported outcomes (PROs) showed improvement, with no significant increase in fatty infiltration, suggesting that functional recovery may occur despite structural deficits.