The Femoral Impingement Index Predicts Inferior Clinical Outcomes in Men Undergoing Hip Arthroscopy for Femoroacetabular Impingement Syndrome.

Purpose

To evaluate the association of femoral version, McKibbin index, and femoral impingement index (FII) on patient-reported outcomes after primary hip arthroscopy for femoroacetabular impingement syndrome.

Methods

We retrospectively reviewed prospectively collected data from a hip preservation registry. Inclusion criteria included Tönnis grade ≤1 and a minimum 2-year follow-up. Computed tomography-based morphologic parameters and validated patient-reported outcomes (modified Harris Hip Score, hip outcome score-activities of daily living, hip outcome score-sport-specific subscale, and International Hip Outcome Tool) were analyzed. Patients were stratified by femoral version, McKibbin index, and FII (low <45°, moderate 45°-75°, high >75°). Multivariable regression adjusted for age and preoperative scores was used to assess outcomes and achievement of the minimal clinically important difference.

Results

A total of 456 hips met inclusion criteria, with significant improvements across all outcome measures at a mean follow-up of 2.6 years (P < .001). No significant differences in outcomes were observed when stratified by femoral version or McKibbin index. However, patients with high FII (>75°), predominantly men, displayed lower net improvement in hip outcome score-sport-specific subscale scores (14.6 vs 28.1 and 33.4 in moderate and low FII groups, respectively; P = .024) and reduced odds of achieving the minimal clinically important difference (53% vs 75% in low FII group; P = .047). Among men, increasing FII was associated with significantly lower improvements in hip outcome score-activities of daily living and hip outcome score-sport-specific subscale scores and lower likelihood of achieving minimal clinically important difference (adjusted odds ratio 0.19; 95% confidence interval 0.04-0.83; P = .028).

Conclusions

In this cohort, a high FII (>75°) was associated with significantly lower net patient-reported outcome measure improvement in male patients. LEVEL OF EVIDENCE Level III, retrospective cohort study.