Limited External Rotation and Hip Extension Due to Posterior Extra-articular Ischiofemoral Hip Impingement in Female Patients With Increased Femoral Anteversion: Implications for Sports, Sexual, and Daily Activities

Background: Posterior femoroacetabular impingement (FAI) is poorly understood. Patients with increased femoral anteversion (FV) exhibit posterior hip pain. Purpose: To correlate hip impingement area with FV and with combined version and to investigate frequency of limited external rotation (ER) and hip extension (<40 degrees, <20 degrees, and <0 degrees) due to posterior extra-articular ischiofemoral impingement. Study Design: Cross-sectional study; Level of evidence, 3. Methods: Osseous patient-specific three-dimensional (3D) models based on 3D computed tomography scans were generated of 37 female patients (50 hips) with positive posterior impingement test (100%) and increased FV >35 degrees (Murphy method). Surgery was performed in 50% of patients (mean age, 30 years; 100% female). FV and acetabular version (AV) were added to calculate combined version. Subgroups of patients (24 hips) with increased combined version >70 degrees and patients (9 valgus hips) with increased combined version >50 degrees were analyzed. The control group (20 hips) had normal FV, normal AV, and no valgus. Bone segmentation was performed to generate 3D models of every patient. Validated 3D collision detection software was used for simulation of impingement-free hip motion (equidistant method). Impingement area was evaluated in combined 20 degrees of ER and 20 degrees of extension. Results: Posterior extra-articular ischiofemoral impingement occurred between the ischium and the lesser trochanter in 92% of patients with FV >35 degrees in combined 20 degrees of ER and 20 degrees of extension. Impingement area in combined 20 degrees of ER and 20 degrees of extension was larger with increasing FV and with higher combined version; correlation was significant (P < .001, r = 0.57, and r = 0.65). Impingement area was significantly (P = .001) larger (681 vs 296 mm(2)) for patients with combined version >70 degrees (vs <70 degrees, respectively) in combined 20 degrees of ER and 20 degrees of extension. All symptomatic patients with increased FV >35 degrees (100%) had limited ER <40 degrees, and most (88%) had limited extension <40 degrees. The frequency of posterior intra- and extra-articular hip impingement of symptomatic patients (100% and 88%, respectively) was significantly (P < .001) higher compared with the control group (10% and 10%, respectively). The frequency of patients with increased FV >35 degrees with limited extension <20 degrees (70%) and patients with limited ER <20 degrees (54%) was significantly (P < .001) higher compared with the control group (0% and 0%, respectively). The frequency of completely limited extension <0 degrees (no extension) and ER <0 degrees (no ER in extension) was significantly (P < .001) higher for valgus hips (44%) with combined version >50 degrees compared with patients with FV >35 degrees (0%). Conclusion: All patients with increased FV >35 degrees had limited ER <40 degrees, and most of them had limited extension <20 degrees due to posterior intra- or extra-articular hip impingement. This is important for patient counselling, for physical therapy, and for planning of hip-preservation surgery (eg, hip arthroscopy). This finding has implications and could limit daily activities (long-stride walking), sexual activity, ballet dancing, and sports (eg, yoga or skiing), although not studied directly. Good correlation between impingement area and combined version supports evaluation of combined version in female patients with positive posterior impingement test or posterior hip pain.