Background: Symptomatic patients with femoroacetabular impingement (FAI) have limitations in daily activities and sports and report the exacerbation of hip pain in deep flexion. Yet, the exact impingement location in deep flexion and the effect of femoral version (FV) are unclear. Purpose: To investigate the acetabular and femoral locations of intra- or extra-articular hip impingement in flexion in patients with FAI with and without femoral retroversion. Study Design: Cross-sectional study; Level of evidence, 3. Methods: An institutional review board–approved retrospective study involving 84 hips (68 participants) was performed. Of these, symptomatic patients (37 hips) with anterior FAI and femoral retroversion (FV <5°) were compared with symptomatic patients (21 hips) with anterior FAI (normal FV) and with a control group (26 asymptomatic hips without FAI and normal FV). All patients were symptomatic, had anterior hip pain, and had positive anterior impingement test findings. Most of the patients had hip/groin pain in maximal flexion or deep flexion or during sports. All 84 hips underwent pelvic computed tomography (CT) to measure FV as well as validated dynamic impingement simulation with patient-specific CT-based 3-dimensional models using the equidistant method. Results: In maximal hip flexion, femoral impingement was located anterior-inferior at 4 o’clock (57%) and 5 o’clock (32%) in patients with femoral retroversion and mostly at 5 o’clock in patients without femoral retroversion (69%) and in asymptomatic controls (76%). Acetabular intra-articular impingement was located anterior-superior (2 o’clock) in all 3 groups. In 125° of flexion, patients with femoral retroversion had a significantly ( P < .001) higher prevalence of anterior extra-articular subspine impingement (54%) and anterior intra-articular impingement (89%) compared with the control group (29% and 62%, respectively). Conclusion: Knowing the exact location of hip impingement in deep flexion has implications for surgical treatment, sports, and physical therapy and confirms previous recommendations: Deep flexion (eg, during squats/lunges) should be avoided in patients with FAI and even more in patients with femoral retroversion. Patients with femoral retroversion may benefit and have less pain when avoiding deep flexion. For these patients, the femoral location of the impingement conflict in flexion was different (anterior-inferior) and distal to the cam deformity compared with the location during the anterior impingement test (anterior-superior). This could be important for preoperative planning and bone resection (cam resection or acetabular rim trimming) during hip arthroscopy or open hip preservation surgery to ensure that the region of impingement is appropriately identified before treatment.

Frequencies of combined abnormalities of femoral version (FV) and acetabular version (AV) and of abnormalities of the McKibbin index are unknown. To investigate the prevalence of combined abnormalities of FV and AV and of abnormalities of the McKibbin index in symptomatic patients with femoroacetabular impingement (FAI), a retrospective, Institutional Review Board (IRB)-approved study of 333 symptomatic patients (384 hips) that were presented with hip pain and FAI was performed. The computed tomography/magnetic resonance imaging based measurement of central AV, cranial AV and FV was compared among five subgroups with distinguished FAI subgroups and patients that underwent a hip preservation surgery. The allocation to each subgroup was based on AP radiographs. Normal AV and FV were 10–25°. The McKibbin index is the sum of central AV and FV. Of patients that underwent a hip preservation surgery, 73% had a normal McKibbin index (20–50°) but 27% had an abnormal McKibbin index. Of all patients, 72% had a normal McKibbin index, but 28% had abnormal McKibbin index. The prevalence of combined abnormalities of FV and AV varied among subgroups: a higher prevalence of decreased central AV combined with decreased FV of patients with acetabular-retroversion group (12%) and overcoverage (11%) was found compared with mixed-type FAI (5%). Normal AV combined with normal FV was present in 41% of patients with cam-type FAI and in 34% of patients with overcoverage. Patients that underwent a hip preservation surgery had normal mean FV (17 ± 11°), central AV (19 ± 7°), cranial AV (16 ± 10°) and McKibbin index (36 ± 14°). Frequency of combined abnormalities of AV and FV differs between subgroups of FAI patients. Aggravated and compensated McKibbin index was prevalent in FAI patients. This has implications for open hip preservation surgery (surgical hip dislocation or femoral derotation osteotomy) or hip arthroscopy or non-operative treatment.

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°, <20°, and <0°) 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° (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° and patients (9 valgus hips) with increased combined version >50° 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° of ER and 20° of extension. Results: Posterior extra-articular ischiofemoral impingement occurred between the ischium and the lesser trochanter in 92% of patients with FV >35° in combined 20° of ER and 20° of extension. Impingement area in combined 20° of ER and 20° 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 mm2) for patients with combined version >70° (vs <70°, respectively) in combined 20° of ER and 20° of extension. All symptomatic patients with increased FV >35° (100%) had limited ER <40°, and most (88%) had limited extension <40°. 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° with limited extension <20° (70%) and patients with limited ER <20° (54%) was significantly ( P < .001) higher compared with the control group (0% and 0%, respectively). The frequency of completely limited extension <0° (no extension) and ER <0° (no ER in extension) was significantly ( P < .001) higher for valgus hips (44%) with combined version >50° compared with patients with FV >35° (0%). Conclusion: All patients with increased FV >35° had limited ER <40°, and most of them had limited extension <20° 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.

Background: It remains unclear if femoral retroversion is a contraindication for hip arthroscopy in patients with femoroacetabular impingement (FAI). Purpose: To compare the area and location of hip impingement at maximal flexion and during the FADIR test (flexion, adduction, internal rotation) in FAI hips with femoral retroversion, hips with decreased combined version, and asymptomatic controls. Study Design: Cross-sectional study; Level of evidence, 3. Methods: Twenty-four symptomatic patients (37 hips) with anterior FAI were evaluated. All patients had femoral version (FV) <5° according to the Murphy method. Two subgroups were analyzed: 13 hips with absolute femoral retroversion (FV <0°) and 29 hips with decreased combined version (McKibbin index <20°). All patients were symptomatic and had anterior groin pain and a positive anterior impingement test ; all had undergone pelvic computed tomography (CT) scans to measure FV. The asymptomatic control group consisted of 26 hips. Dynamic impingement simulation of maximal flexion and FADIR test at 90° of flexion was performed with patient-specific CT-based 3-dimensional models. Extra- or intra-articular hip impingement area and location were compared between the subgroups and with control hips using nonparametric tests. Results: Impingement area was significantly larger for hips with decreased combined version (<20°) versus combined version (≥20°) (mean ± SD; 171 ± 140 vs 78 ± 55 mm2; P = .012) and was significantly larger for hips with FV <0° (absolute femoral retroversion) vs FV >0° ( P = .025). Hips with absolute femoral retroversion had a significantly higher frequency of extra-articular subspine impingement versus controls (92% vs 0%; P < .001), compared to 84% of patients with decreased combined version. Intra-articular femoral impingement location was most often (95%) anterosuperior and anterior (2-3 o’clock). Anteroinferior femoral impingement location was significantly different at maximal flexion (anteroinferior [4-5 o’clock]) versus the FADIR test (anterosuperior and anterior [2-3 o’clock]) ( P < .001). Conclusion: Patients with absolute femoral retroversion (FV <0°) had a larger hip impingement area, and most exhibited extra-articular subspine impingement. Preoperative FV assessment with advanced imaging (CT/magnetic resonance imaging) could help to identify these patients (without 3-dimensional modeling). Femoral impingement was located anteroinferiorly at maximal flexion and anterosuperiorly and anteriorly during the FADIR test.

Background: The location of posterior hip impingement at maximal extension in patients with posterior femoroacetabular impingement (FAI) is unclear. Purpose: To investigate the frequency and area of impingement at maximal hip extension and at 10° and 20° of extension in female patients with increased femoral version (FV) and posterior hip pain. Study Design: Cross-sectional study; Level of evidence, 3. Methods: Osseous patient-specific 3-dimensional (3D) models were generated of 50 hips (37 female patients, 3D computed tomography) with a positive posterior impingement test and increased FV (defined as >35°). The McKibbin index (combined version) was calculated as the sum of FV and acetabular version (AV). Subgroups of patients with an increased McKibbin index >70° (24 hips) and FV >50° (20 hips) were analyzed. A control group of female participants (10 hips) had normal FV, normal AV, and no valgus deformity (neck-shaft angle, <139°). Validated 3D collision detection software was used for simulation of osseous impingement-free hip extension (no rotation). Results: The mean impingement-free maximal hip extension was significantly lower in patients with FV >35° compared with the control group (15° ± 15° vs 55° ± 19°; P < .001). At maximal hip extension, 78% of patients with FV >35° had osseous posterior extra-articular ischiofemoral hip impingement. At 20° of extension, the frequency of posterior extra-articular ischiofemoral impingement was significantly higher for patients with a McKibbin index >70° (83%) and for patients with FV >35° (76%) than for controls (0%) ( P < .001 for both). There was a significant correlation between maximal extension (no rotation) and FV ( r = 0.46; P < .001) as well as between impingement area at 20° of extension (external rotation [ER], 0°) and McKibbin index (0.61; P < .001). Impingement area at 20° of extension (ER, 0°) was significantly larger for patients with McKibbin index >70° versus <70° (251 vs 44 mm2; P = .001). Conclusion: The limited hip extension found in our study could theoretically affect the performance of sports activities such as running, ballet dancing, or lunges. Therefore, although not examined directly in this study, these activities are not advisable for these patients. Preoperative evaluation of FV and the McKibbin index is important in female patients with posterior hip pain before hip preservation surgery (eg, hip arthroscopy).