Association Between Orientation and Magnitude of Femoral Torsion and Propensity for Clinically Meaningful Improvement After Hip Arthroscopy for Femoroacetabular Impingement Syndrome: A Computed Tomography Analysis

Background: Femoral torsion imaging measurements and classifications are heterogeneous throughout the literature, and the influence of femoral torsion on clinically meaningful outcome improvement after hip arthroscopy for femoroacetabular impingement syndrome (FAIS) has not been well studied. Purpose: To (1) perform a computed tomography (CT)-based analysis to quantify femoral torsion in patients with FAIS and (2) explore the relationship between the orientation and magnitude of femoral torsion and the propensity for clinically meaningful outcome improvement after hip arthroscopy. Study Design: Cohort study; Level of evidence, 3. Methods: Consecutive patients who underwent hip arthroscopy for FAIS between January 2012 and April 2018 were identified. Inclusion criteria were the presence of preoperative CT imaging with transcondylar slices of the knee and minimum 2-year outcome measures. Exclusion criteria were revision hip arthroscopy, Tonnis grade >1, congenital hip condition, hip dysplasia (lateral center-edge angle <20 degrees), and concomitant gluteus medius or minimus repair. Torsion groups were defined as severe retrotorsion (SR; <0 degrees), moderate retrotorsion (MR; 0 degrees-5 degrees), normal torsion (N; 5 degrees-20 degrees), moderate antetorsion (MA; 20 degrees-25 degrees), and severe antetorsion of antetorsion (SA; >25 degrees). Treatment did not differ based on femoral torsion. Patient characteristics and clinical outcomes were analyzed, including the Hip Outcome Score-Activities of Daily Living (HOS-ADL), Hip Outcome Score-Sports Subscale (HOS-SS), modified Harris Hip Score (mHHS), international Hip Outcome Tool (iHOT-12), visual analog scale (VAS) for pain, and VAS for satisfaction. Achievement of the minimal clinically important difference (MCID) and patient acceptable symptom state (PASS) by torsion stratification was analyzed using the chi-square test. Inter- and intrarater reliabilities for CT measurements were 0.980 (P < .001) and 0.974 (P < .001), respectively. Results: The study included 573 patients with a mean +/- SD age and body mass index of 32.6 +/- 11.8 years and 25.6 +/- 10.6, respectively. The mean +/- SD femoral torsion for the study population was 12.3 degrees +/- 9.3 degrees. After stratification, the number of patients within each group and the mean +/- SD torsion for each group were as follows: SR (n = 36; -6.5 degrees +/- 7.1 degrees), MR (n = 80; 2.8 degrees +/- 1.4 degrees), N (n = 346; 12.3 degrees +/- 4.1 degrees), MA (n = 64; 22.2 degrees +/- 1.4 degrees), and SA (n = 47; 30.3 degrees +/- 3.7 degrees). No significant differences in age, body mass index, sex, tobacco use, workers' compensation status, or participation in physical activity were observed at baseline. No significant differences were seen in pre- and postoperative VAS pain, mHHS, HOS-ADL, HOS-SS, iHOT-12, or postoperative VAS satisfaction among the cohorts. Furthermore, no statistically significant differences were found in the proportion of patients who achieved the MCID or the PASS for any outcome among the groups. Conclusion: The orientation and severity of femoral torsion at the time of hip arthroscopy for FAIS did not influence the propensity for clinically significant outcome improvement.