Imaging Markers of Hip Instability are Associated with Worse Outcomes at Two to Four-year Follow-up in Female Patients Undergoing Hip Arthroscopy for Femoroacetabular Impingement

OBJECTIVES: To investigate the effect of radiographic markers of hip instability on outcomes of female patients undergoing hip arthroscopy for femoroacetabular impingement. METHODS: This was a retrospective reviewof a prospectively collected cohort of females undergoing hip arthroscopy with a diagnosis of FAI treated with femoral osteoplasty with or without labral repair. iHOT-12 was collected preoperatively and at 2 to 4-year follow-up. Radiographs were reviewed and anterior wall index (AWI), posterior wall index (PWI), femoro-epiphyseal acetabular roof (FEAR) index, and lateral center edge angle (LCEA) were recorded in all patients. Computed tomography was used to quantify femoral anteversion in all patients. A laterally oriented FEAR index is considered positive (unstable), while a medially oriented fear index is considered negative (impingement/stable). An AWI of <0.30 and a PWI<0.80 were considered anterior wall deficient (AWD) and posterior wall deficient (PWD), respectively. Patients with borderline acetabular dysplasia (LCEA≤25) were groups as medially or laterally oriented FEAR index. Similarly, patients with borderline acetabular dysplasia(LCEA≤25) were groups as elevated femoral anteversion (>15 degrees) or not. Differences in means were tested using a students t-test or an analysis of variance with a post-hoc tukey’s test. RESULTS: There were 175 Female patients with a mean age of 33 years. Mean follow up was 34.6 months. Mean preoperative iHOT12 was 30.4. Mean postoperative iHOT12 was 74.8. Mean FA was 11.7 (Range 1 to 34) degrees. There were 64 patients with an LCEA≤25, 138 patients had no AWD or PWD, 18 patients with an AWI <0.30 and 18 patients with a PWI <0.80. One patient was excluded from the analysis for having both an AWI<0.30 and a PWI<0.8. Patients with AWD had lower mean iHOT at follow up (54.5 compared with those with no wall deficiency 77.7, p=0.001.) Patents with PWD did not (72.4 compared with those with no wall deficiency 77.7, p=0.669.) Similarly, patients with AWD had lower mean iHOT improvement at follow up (24.2 compared with those with no wall deficiency 47.0, p=0.001). Patents with PWD did not (43.1 compared with those with no wall deficiency 47.0, p=0.808). Mean FEAR index was -7.1(Range -30 to 15) degrees. The FEAR index correlated with both the iHOT12 at follow up (-0.171, p=0.024) and the improvement in the iHOT12(-0.192, p=0.011). There were 31 patients with a laterally oriented FEAR index. These patients had worse iHOT12 at follow-up (64.9 points versus 77.0 points, p=0.037) and less improvement in iHOT12 (34.3 points versus 46.6 points, p=0.015). There were 110 patients with LCEA>25, 42 patients with LCEA≤25 with a medially oriented FEAR index and 23 patients with an LCEA≤25 with a laterally oriented FEAR index. Patients with LCEA≤25 and a laterally oriented FEAR index had worse iHOT12 at follow-up (60.7 points versus 78.9 points, p=0.005) and less improvement in iHOT12 from surgery (30.0 points versus 49.5 points, p=0.002) compared to those with an LCEA>25. There were 110 patients with LCEA>25, 46 patients with LCEA≤25 and FA <15 degrees and 17 patients with LCEA≤25 and FA≥15 degrees. Patients with LCEA≤25 had worse iHOT12 at follow-up (68.0 points versus 78.9 points, p=0.010) and less improvement in iHOT12 from surgery (36.0 points versus 49.5 points, p=0.001) compared to those with an LCEA>25. Patients with LCEA≤25 and FA≥15 degrees had worse iHOT12 at follow-up (59.5 points versus 78.9 points, p=0.008) and less improvement in iHOT12 from surgery (28.2 points versus 49.5 points, p=0.003) compared to those with an LCEA>25. In addition, patients with LCEA≤25 and FA<15 degrees had less improvement iHOT12 from surgery (38.0 points versus 49.4 points, p=0.026) compared to those with an LCEA>25. CONCLUSION: Imaging markers of hip instability, including borderline acetabular dysplasia, increased femoral anteversion, a laterally oriented FEAR index, and anterior wall deficiency are predictive of worse outcomes of hip arthroscopy for FAI in female patients. A more thoughtful imaging analysis of female patients preoperatively may identify patients at risk of worse outcomes after hip arthroscopy and may guide treatment with other joint preserving procedures, including periacetabular or femoral osteotomy.