Background: Variations in femoral and acetabular version are becoming increasingly recognized as contributing factors to the development of hip pain in patients with femoroacetabular impingement (FAI) and hip dysplasia. It is still unknown what the true prevalence of these rotational abnormalities is in this patient population. Purpose: To determine (1) the prevalence of femoral version abnormalities in symptomatic hips with FAI and hip dysplasia, (2) the prevalence of combined abnormalities of femoral and acetabular version in these patients, and (3) which specific hip morphologies are associated with abnormalities of femoral version. Study Design: Cross-sectional study; Level of evidence, 3. Methods: A total of 462 symptomatic patients (538 hips) were included who had hip pain attributed to FAI or hip dysplasia and who presented to our tertiary referral center for hip preservation surgery between 2011 and 2015. We retrospectively examined femoral and acetabular version among 11 subgroups with predefined hip morphologies and compared findings with a control group. The allocation to each subgroup was based on morphologic reference values for femoral head coverage, lateral center edge angle, alpha angle, and neck-shaft angle calculated on plain radiographs. Results: Of the 538 hips included, 52% were found to have abnormal femoral version; severe abnormalities were found in 17%. Severely decreased femoral version (35°), in 12%. The most frequent abnormal combination was increased femoral version combined with normal acetabular version (22%). We found significantly lower mean femoral version for the cam-type FAI group (15°) and significantly higher mean femoral version for the Perthes hips (32°; ie, Legg-Calvé-Perthes disease) as compared with the control group (22°). The mean femoral version of the study group was 19°; for male patients, 15°; and for female patients, 22°. Conclusion: Abnormalities in femoral version are highly prevalent in patients with hip pain who are eligible for hip preservation surgery, and severe abnormalities are prevalent in 1 of 6 patients (17%). Based on these results, the evaluation of young patients with hip pain should always include an assessment of femoral version and acetabular version to best decide what treatment approach should be undertaken to optimize outcomes.

It remains unclear whether decreased femoral version (FV) causes anterior intra- or extra-articular femoroacetabular impingement (FAI). Therefore, we evaluated symptomatic hips with decreased FV, with and without cam and pincer FAI, by using computed tomography (CT)–based virtual 3-dimensional (3D) impingement simulation and compared this group with patients with normal FV and with asymptomatic hips. To investigate (1) the osseous range of motion, (2) the osseous femoral and acetabular impingement zones, and (3) whether hip impingement is extra- or intra-articular in symptomatic hips with FAI. Cross-sectional study; Level of evidence, 3. An institutional review board–approved, retrospective comparative analysis was performed on a total of 84 hips in 68 participants. Of these, 37 hips in 24 symptomatic patients with FAI had decreased FV. These hips were compared with 21 hips of 18 symptomatic patients with anterior FAI with normal FV (10°-25°) and 26 asymptomatic hips with no FAI and normal FV. All patients with FAI were symptomatic and had anterior hip pain and a positive anterior impingement test. They underwent pelvic CT scans to measure FV. Decreased FV was defined as FV less than 5°. The 37 hips with decreased FV presented both with and without cam and pincer FAI. All 84 hips were evaluated by use of CT-based 3D models and a validated 3D range of motion and impingement simulation. Asymptomatic hips were contralateral normal hips imaged in patients undergoing total hip arthroplasty. Hips with FAI combined with decreased FV had a significantly (P < .001) lower mean flexion (114°± 8° vs 125°± 13°) and internal rotation (IR) at 90° of flexion (18°± 6° vs 32°± 9°, P < .001) compared with the asymptomatic control group. Symptomatic patients with FAI and normal FV had flexion of 120°± 16° and IR at 90° of flexion of 23°± 15°. In a subgroup analysis, we found a significantly (P < .001) lower IR in 90° of flexion in hips with FV less than 5° combined with mixed-type FAI compared with hips with FV less than 5° without a cam- or pincer-type deformity. The maximal acetabular impingement zone for hips with decreased FV was located at the 2-o’clock position and ranged from 1 to 3 o’clock. In hips with decreased FV, most of the impingement locations were intra-articular but 32% of hips had combined intra- and extra-articular FAI in internal rotation in 90° of flexion. During the flexion-adduction-IR test performed in 10° and 20° of adduction, extra-articular subspine FAI had significantly (P < .001) higher prevalence (68% and 84%) in hips with decreased FV compared with normal hips. Hips with FAI and decreased FV had less flexion and internal rotation in 90° of flexion compared with the asymptomatic control group. The majority of hip impingement due to low FV was intra-articular, but one-third of samples had combined intra- and extra-articular subspine FAI. Anterior extra- and intra-articular hip impingement can be present in patients who have FAI with decreased FV. This could be important for patients undergoing hip arthroscopy.

Femoroacetabular impingement (FAI) is a complex 3-dimensional (3D) hip abnormality that can cause hip pain and osteoarthritis in young and active patients of childbearing age. Imaging is static and based on 2-dimensional radiographs or computed tomography (CT) scans. Recently, CT-based 3D impingement simulation was introduced for patient-specific assessments of hip deformities, whereas magnetic resonance imaging (MRI) offers a radiation-free alternative for surgical planning before hip arthroscopic surgery. To (1) investigate the difference between 3D models of the hip, (2) correlate the location of hip impingement and range of motion (ROM), and (3) correlate diagnostic parameters while comparing CT- and MRI-based osseous 3D models of the hip in symptomatic patients with FAI. Cohort study (Diagnosis); Level of evidence, 2. The authors performed an institutional review board–approved comparative and retrospective study of 31 hips in 26 symptomatic patients with FAI. We compared CT- and MRI-based osseous 3D models of the hip in the same patients. 3D CT scans (slice thickness, 1 mm) of the entire pelvis and the distal femoral condyles were obtained. Preoperative MRI of the hip was performed including an axial-oblique T1 VIBE sequence (slice thickness, 1 mm) and 2 axial anisotropic (1.2 × 1.2 × 1 mm) T1 VIBE Dixon sequences of the entire pelvis and the distal femoral condyles. Threshold-based semiautomatic reconstruction of 3D models was performed using commercial software. CT- and MRI-based 3D models were compared with specifically developed software. (1) The difference between MRI- and CT-based 3D models was less than 1 mm for the proximal femur and the acetabulum (median surface distance, 0.4 ± 0.1 mm and 0.4 ± 0.2 mm, respectively). (2) The correlation for ROM values was excellent (r = 0.99, P < .001) between CT and MRI. The mean absolute difference for flexion and extension was 1.9°± 1.5° and 2.6°± 1.9°, respectively. The location of impingement did not differ between CT- and MRI-based 3D ROM analysis in all 12 of 12 acetabular and 11 of 12 femoral clock-face positions. (3) The correlation for 6 diagnostic parameters was excellent (r = 0.98, P < .001) between CT and MRI. The mean absolute difference for inclination and anteversion was 2.0°± 1.8° and 1.0°± 0.8°, respectively. Patient-specific and radiation-free MRI-based dynamic 3D simulation of hip impingement and ROM can replace CT-based 3D simulation for patients with FAI of childbearing age. On the basis of these excellent results, we intend to change our clinical practice, and we will use MRI-based 3D models for future clinical practice instead of CT-based 3D models. This allows radiation-free and patient-specific preoperative 3D impingement simulation for surgical planning and simulation of open hip preservation surgery and hip arthroscopic surgery.

The past 2 decades have seen a substantial increase in hip joint preserving procedures, primarily secondary to not only hip dysplasia, but the recognition and description of femoroacetabular impingement (FAI), and its association with chondral lesions, as a potentially pre-arthritic condition. Morphological magnetic resonance imaging (MRI) plays an essential role in the preoperative assessment of osseous deformities and in particular of the resulting joint degeneration. An accurate descriptive report of chondrolabral lesions is warranted describing the tear pattern, size, localization, and extension of the lesions. This is important because different damage patterns and localization of the lesions may determine the surgical approach. The current imaging standard is direct magnetic resonance arthrography (MRA) with a small field of view, with acquisition of radial images in addition to the classic coronal, sagittal, and axial-oblique images. Early cartilage damage detected on direct MRA obtained with or without traction can predict long-term failure after FAI surgery.

Posterior extra-articular hip impingement has been described for valgus hips with increased femoral version (FV). These patients can present clinically with lack of external rotation (ER) and extension and with a positive posterior impingement test. But we do not know the effect of the combination of deformities, and the impingement location in early flexion is unknown. To evaluate patient-specific 3-dimensional computed tomography (3D CT) scans of hips with increased FV and control hips for differences in range of motion, location and prevalence of osseous posterior intra- and extra-articular hip impingement. Case series; Level of evidence, 4. Osseous 3D models based on segmentation of 3D CT scans were analyzed for 52 hips (38 symptomatic patients) with positive posterior impingement test and increased FV (>35°). There were 26 hips with an increased McKibbin instability index >70 (unstable hips). Patients were mainly female (96%), with an age range of 18 to 45 years. Of them, 21 hips had isolated increased FV (>35°); 22 hips had increased FV and increased acetabular version (AV; >25°); and 9 valgus hips (caput-collum-diaphyseal angle >139°) had increased FV and increased AV. The control group consisted of 20 hips with normal FV, normal AV, and no valgus (caput-collum-diaphyseal angle <139°). Validated 3D CT–based collision detection software for impingement simulation was used to calculate impingement-free range of motion and location of hip impingement. Surgical treatment was performed after the 3D CT–based impingement simulation in 27 hips (52%). Hips with increased FV had significantly (P < .001) decreased extension and ER at 90° of flexion as compared with the control group. Posterior impingement was extra-articular (92%) in hips with increased FV. Valgus hips with increased FV and AV had combined intra- and extra-articular impingement. Posterior hip impingement occurred between the ischium and the lesser trochanter at 20° of extension and 20° of ER. Impingement was located between the ischium and the greater trochanter or intertrochanteric area at 20° of flexion and 40° of ER, with a modification of the flexion-abduction-ER (FABER) test. Posterior extra-articular ischiofemoral hip impingement can be caused by the lesser and greater trochanter or the intertrochanteric region. We recommend performing the modified FABER test during clinical examination in addition to the posterior impingement test for female patients with high FV. In addition, 3D CT can help for surgical planning, such as femoral derotation osteotomy and/or hip arthroscopy or resection of the lesser trochanter.

Aims: The prevalence of combined abnormalities of femoral torsion (FT) and tibial torsion (TT) is unknown in patients with femoroacetabular impingement (FAI) and hip dysplasia. This study aimed to determine the prevalence of combined abnormalities of FT and TT, and which subgroups are associated with combined abnormalities of FT and TT. Methods: We retrospectively evaluated symptomatic patients with FAI or hip dysplasia with CT scans performed between September 2011 and September 2016. A total of 261 hips (174 patients) had a measurement of FT and TT. Their mean age was 31 years (SD 9), and 63% were female (165 hips). Patients were compared to an asymptomatic control group (48 hips, 27 patients) who had CT scans including femur and tibia available for analysis, which had been acquired for nonorthopaedic reasons. Comparisons were conducted using analysis of variance with Bonferroni correction. Results: In the overall study group, abnormal FT was present in 62% (163 hips). Abnormal TT was present in 42% (109 hips). Normal FT combined with normal TT was present in 21% (55 hips). The most frequent abnormal combination was increased FT combined with normal TT of 32% (84 hips). In the hip dysplasia group, 21% (11 hips) had increased FT combined with increased TT. The prevalence of abnormal FT varied significantly among the subgroups (p < 0.001). We found a significantly higher mean FT for hip dysplasia (31°; SD 15)° and valgus hips (42° (SD 12°)) compared with the control group (22° (SD 8°)). We found a significantly higher mean TT for hips with cam-type-FAI (34° (SD 6°)) and hip dysplasia (35° (SD 9°)) compared with the control group (28° (SD 8°)) (p < 0.001). Conclusion: Patients with FAI had a high prevalence of combined abnormalities of FT and TT. For hip dysplasia, we found a significantly higher mean FT and TT, while 21% of patients (11 hips) had combined increased TT and increased FT (combined torsional malalignment). This is important when planning hip preserving surgery such as periacetabular osteomy and femoral derotation osteotomy. Cite this article: Bone Joint J 2020;102-B(12):1636–1645.