Femoroacetabular Impingement Patients With Decreased Femoral Version Have Different Impingement Locations and Intra- and Extraarticular Anterior Subspine FAI on 3D-CT-Based Impingement Simulation: Implications for Hip Arthroscopy

Associations between hip cartilage lesions and morphologic parameters of bony structures in a cohort of Asian patients with labral tears measured using a computed tomography-based software system

OBJECTIVE

This study aimed to investigate the associations between hip cartilage lesions and bony morphologic parameters in the hip joints using a computed tomography-based software system.

METHODS

Seventy-nine symptomatic hips that underwent hip arthroscopic labral preservation surgery were enrolled in this study. Bony structural morphologic parameters were subsequently assessed via a computed tomography-based software system. The indices included the femoral neck anteversion (FNA), alpha angle (AA) at each o'clock position of the femoral head, lateral center-edge angle (LCEA), and three-dimensional acetabular coverage (3D-AC). Cartilage damage was confirmed arthroscopically and classified according to the Multicenter Arthroscopy of the Hip Outcome Research Network (MAHORN) classification as well as the International Cartilage Repair Society classification.

RESULTS

Of the 79 hips, 41 patients were male, and 38 were female, with a mean age of 39.1 years ​±16.1 years (11-78). The mean LCEA was 27.6° ​± ​8.6° (range 7°-46°), and the mean FNA was 22.9° ​± ​14.4° (range -2°-63°). Grade 4 or 5 MAHORN acetabulum cartilage lesions were observed in 10 hips (13 ​%), while femoral head cartilage lesions with ICRS grade of 3 or 4 were found in 10 hips. Patients with MAHORN grade 4 or 5 cartilage lesions had significantly greater FNA compared with those with MAHORN grade 0 to 3 lesions (32.6° ​± ​10.3° versus 21.4° ​± ​14.4°, p ​= ​0.009). Although patients with MAHORN grade 4 or 5 lesions had greater AA at the entire o'clock of the femoral neck, the difference was not statistically significant. Patients whose FNAs were 26° or larger had a 6.2-fold greater odds ratio (95 ​% confidence interval, 1.2-31.5) of acetabular cartilage damage than those whose FNAs were less than 26° (p ​= ​0.015).

CONCLUSION

The use of computed tomography-based software provided detailed insights into bony abnormalities reinforcing its utility in evaluating hip joint pathologies and their relationship with cartilage lesions.

LEVEL OF EVIDENCE

Level III.

Femoroacetabular Impingement: Preoperative Planning and Postoperative MR Imaging Evaluation

Imaging plays a critical role in the preoperative and postoperative evaluation of patients with femoroacetabular impingement. Non-contrast MR imaging and direct magnetic resonance arthrography of the hip are the modalities of choice for the preoperative assessment of chondrolabral lesions. The MRI protocol should include radial images for detailed analysis of the cam deformity and fast sequences covering the pelvis and knee for measurement of femoral torsion. In patients with postoperative pain, a comprehensive analysis of residual deformities and signs of osseous overcorrection should be performed as they can cause residual impingement or iatrogenic instability.

Simulation of hip bony range of motion (BROM) corresponds to the observed functional range of motion (FROM) for pure flexion, internal rotation in deep flexion, and external rotation in minimal flexion-extension - A cadaver study

BACKGROUND

The study investigated the relationship between computed bony range of motion (BROM) and actual functional range of motion (FROM) as directly measured in cadaveric hips. The hypothesis was that some hip movements are not substantially restricted by soft tissues, and therefore, computed BROM for these movements may effectively represent FROM, providing a reliable parameter for computational pre-operative planning.

METHODS

Maximum passive FROM was measured in nine cadaveric hips using optical tracking. Each hip was measured in at least ninety FROM positions, covering flexion, extension, abduction, flexion-internal rotation (IR), flexion-external rotation (ER), extension-IR, and extension-ER movements. The measured FROM was virtually recreated using 3D models of the femur and pelvis derived from CT scans, and the corresponding BROM was computed. The relationship between FROM and BROM was classified into three groups: close (mean difference<5°), moderate (mean difference 5-15°), and weak (mean difference>15°).

RESULTS

The relationship between FROM and BROM was close for pure flexion (difference = 3.1° ± 3.9°) and IR in deep (>70°) flexion (difference = 4.3° ± 4.6°). The relationship was moderate for ER in minimal flexion (difference = 10.3° ± 5.8°) and ER in minimal extension (difference = 11.7° ± 7.2°). Bony impingement was observed in some cases during these movements. Other movements showed a weak relationship: large differences were observed in extension (51.9° ± 14.4°), abduction (18.6° ± 11.3°), flexion-IR at flexion<70° (37.1° ± 9.4°), extension-IR (79.6° ± 4.8°), flexion-ER at flexion>30° (45.9° ± 11.3°), and extension-ER at extension>20° (15.8° ± 4.8°).

CONCLUSION

BROM simulations of hip flexion, IR in deep flexion, and ER in low flexion/extension may be useful in dynamic pre-operative planning of total hip arthroplasty.

How Is Variability in Femoral and Acetabular Version Associated With Presentation Among Young Adults With Hip Pain?

BACKGROUND

Acetabular and femoral version contribute to hip pain in patients with femoroacetabular impingement (FAI) or dysplasia. However, definitions and measurement methods of femoral version have varied in different studies, resulting in different "normal" values being used by clinicians for what should be the same anatomic measurement. This could result in discrepant or even inappropriate treatment recommendations.

QUESTIONS/PURPOSES

In patients undergoing hip preservation surgery, (1) what is the range of acetabular and femoral version at presentation, and how much do two commonly used measurement techniques (those of Murphy and Reikerås) differ? (2) How are differences in acetabular and femoral version associated with clinical factors and outcomes scores at the time of presentation?

METHODS

This was a retrospective analysis of data gathered in a longitudinally maintained database of patients undergoing hip preservation at a tertiary care referral center. Between June 2020 and December 2021, 282 hips in 258 patients were treated for an isolated labral tear (9% [26 hips]), hip dysplasia (21% [59 hips]), FAI (52% [147 hips]), mixed FAI and dysplasia (17% [47 hips]), or pediatric deformity (slipped capital femoral head epiphysis or Perthes disease; 1% [3 hips]) with hip arthroscopy (71% [200 hips]), periacetabular osteotomy (26% [74 hips]), surgical hip dislocation (2.5% [7 hips]), or femoral derotation osteotomy (0.5% [1 hip]). We considered those with complete radiographic data (CT including the pelvis and distal femur) and patient-reported outcome scores as potentially eligible. Exclusion criteria were age younger than 18 or older than 55 years (5 hips, 3 patients), signs of hip osteoarthritis (Tönnis grade ≥ 2; 0), pediatric deformity (slipped capital femoral head epiphysis or Perthes disease; 3 hips, 3 patients), previous femoral or acetabular osteotomy (2 hips, 2 patients), avascular necrosis of the femoral head (0), history of neuromuscular disorder (Ehlers-Danlos syndrome; 3 hips, 3 patients) or rheumatoid disease (ankylosing spondylitis; 1 hip, 1 patient), and when CT did not include the knees (19 hips, 19 patients). Based on these criteria, 249 hips in 227 patients were included. Of patients with bilateral symptomatic hips, one side was randomly selected for inclusion, leaving 227 hips in 227 patients for further analysis. The patients' median age (range) was 34 years (19 to 55 years), the median BMI (range) was 27 kg/m 2 (16 to 55 kg/m 2 ), and 63% (144) were female; they were treated with hip arthroscopy (in 74% [168]) or periacetabular osteotomy (in 23% [52]). Patients underwent a CT scan to measure acetabular version and femoral version using the Murphy (low < 10°; normal: 10° to 25°; high > 25°) or Reikerås (low < 5°; normal: 5° to 20°; high > 20°) technique. The McKibbin index was calculated (low: < 20°; normal: 20° to 50°; high > 50°). Based on the central acetabular version and femoral version as measured by Murphy, hips were grouped according to their rotational profile into four groups: unstable rotational profile: high (high acetabular version with high femoral version) or moderate (high acetabular version with normal femoral version or normal acetabular version with high femoral version); normal rotational profile (normal acetabular version with femoral version); compensatory rotational profile (low acetabular version with high femoral version or high acetabular version with low femoral version); and impingement rotational profile (low acetabular version with low femoral version): high (low acetabular version with low femoral version) or moderate (low acetabular version with normal femoral version or normal acetabular version with low femoral version). Radiographic assessments were manually performed on digitized images by two orthopaedic residents, and 25% of randomly selected measurements were repeated by the senior author, a fellowship-trained hip preservation and arthroplasty surgeon. Interobserver and intraobserver reliabilities were calculated using the correlation coefficient with a two-way mixed model, showing excellent agreement for Murphy technique measurements (intraclass correlation coefficient 0.908 [95% confidence interval 0.80 to 0.97]) and Reikerås technique measurements (ICC 0.938 [95% CI 0.81 to 0.97]). Patient-reported measures were recorded using the International Hip Outcome Tool (iHOT-33) (0 to 100; worse to best).

RESULTS

The mean acetabular version was 18° ± 6°, and mean femoral version was 24° ± 12° using the Murphy technique and 12° ± 11° with the Reikerås method. Eighty percent (181 of 227) of hips had normal acetabular version, 42% (96 of 227) to 63% (142 to 227) had normal femoral version per Murphy and Reikerås, respectively, and 67% (152 to 227) had a normal McKibbin index. Patients with an impingement profile (low acetabular version or femoral version) were older (39 ± 9 years) than patients with an unstable (high acetabular version or femoral version; 33 ± 9 years; p = 0.004), normal (33 ± 9 years; p = 0.02), or compensatory (high acetabular version with low femoral version or vice versa; 33 ± 7 years; p = 0.08) rotational profile. Using the Murphy technique, femoral version was 12° greater than with the Reikerås method (R 2 0.85; p < 0.001). There were no differences in iHOT-33 score between different groups (impingement: 32 ± 17 versus normal 35 ± 21 versus compensated: 34 ± 20 versus unstable: 31 ± 17; p = 0.40).

CONCLUSION

Variability in femoral version is twice as large as acetabular version. Patients with an impingement rotational profile were older than patients with a normal, compensatory, or unstable profile, indicating there are other variables not yet fully accounted for that lead to earlier pain and presentation in these groups. Important differences exist between measurement methods. This study shows that different measurement methods for femoral anteversion result in different numbers; if other authors compare their results to those of other studies, they should use equations such as the one suggested in this study.

LEVEL OF EVIDENCE

Level III, prognostic study.

Femoral Anteversion Angle as a Predictor of Anterior Hip Labral Length in Patients With Femoroacetabular Impingement Syndrome

Background

The relationship between hip rotational abnormalities and hip labral size has not been fully investigated.

Purposes

To (1) examine the correlation between rotational abnormalities of the hip and labral size, while also identifying other predictive values for hip labral size, and (2) explore whether femoral torsion will lead to increased labral size.

Study Design

Cross-sectional study; Level of evidence, 3.

Methods

A total of 180 patients (180 hips) with femoroacetabular impingement syndrome (FAIS) (mean age, 36.81 ± 10.17 years; 67 male, 113 female) who underwent hip arthroscopic surgery between January 2021 and May 2022 were included. The femoral version (FV), acetabular version, and combined version angles were measured on computed tomography, and the labral length and height at the 12-o'clock and 3-o'clock positions were measured on magnetic resonance imaging. The hips were categorized into 3 groups based on FV angle: small (SFV; <10°); moderate (MFV; ≥10° and ≤20°), and large (LFV; >20°), and group comparisons were performed. Linear correlation and regression analysis were employed.

Results

Predictive factors for labral length were FV angle (β = 0.298; P = .02), sex (β = -0.302; P < .001), and age (β = -0.169; P = .016) at 3 o'clock and lateral center-edge angle (LCEA; β = -0.208; P = .005) and age (β = -0.186; P = .011) at 12 o'clock. FV angle was positively correlated with labral length at 3 o'clock (r = 0.267; P < .001) and negatively correlated with age (r = -0.222; P = .003) and female sex (r = -0.202; P = .006). LCEA (r = -0.227; P = .002) and age (r = -0.205; P = .006) were negatively correlated with labral length at 12 o'clock. Labral length at 3 o'clock was significantly different between the LFV (n = 49 hips), MFV (n = 65 hips), and SFV (n = 66 hips) groups (9.85 ± 2.28, 8.89 ± 2.44, and 8.30 ± 2.05 mm, respectively; P = .027 for LFV vs MFV; P < .001 for LFV vs SFV).

Conclusion

Patients with FAIS who exhibited a higher FV angle were at a greater likelihood of having a larger anterior labral length. Increased femoral anteversion and decreased LCEA, male sex, and younger age were significantly associated with longer hip labral length.

Rotational femoral osteotomies and cam resection improve hip function and internal rotation for patients with anterior hip impingement and decreased femoral version

Femoroacetabular impingement (FAI) patients with reduced femoral version (FV) are poorly understood. The aim of this study is to assess (i) hip pain and range of motion, (ii) subjective satisfaction and (iii) subsequent surgeries of symptomatic patients who underwent rotational femoral osteotomies. A retrospective case series involving 18 patients (23 hips, 2014-2018) with anterior hip pain that underwent rotational femoral osteotomies for treatment of decreased FV was performed. The mean preoperative age was 25 ± 6 years (57% male), and all patients had decreased FV < 10° and minimum 1-year follow-up (mean follow-up 2 ± 1 years). Surgical indication was the positive anterior impingement test, limited internal rotation (IR) in 90° of flexion (mean 10 ± 8°) and IR in extension (mean 24 ± 11°), anterosuperior chondrolabral damage in Magnet resonance (MR) arthrography, CT-based measurement of decreased FV (mean 5 ± 3°, Murphy method) and no osteoarthritis (Tönnis Grade 0). Most patients had intra- and extra-articular subspine FAI (patient-specific 3D impingement simulation). Subtrochanteric rotational femoral osteotomies to increase FV (correction 20 ± 4°) were combined with cam resection (78%) and surgical hip dislocation (91%). (i) The positive anterior impingement test decreased significantly (P < 0.001) from pre- to postoperatively (100% to 9%). IR in 90° of flexion increased significantly (P < 0.001, 10 ± 8° to 31 ± 10°). (ii) Subjective satisfaction increased significantly (P < 0.001) from pre- to postoperatively (33% 77%). The mean Merle d'Aubigné and Postel score increased significantly (P < 0.001) from 14 ± 2 (8-15) points to 17 ± 1 (13-18, P < 0.001) points. Most patients (85%) reported at follow-up that they would undergo surgery again. (iii) At follow-up, all 23 hips were preserved (no conversion to total hip arthroplasty). One hip (4%) underwent revision osteosynthesis. Proximal rotational femoral osteotomies combined with cam resection improve hip pain and IR in most FAI patients with decreased FV at short-term follow-up. Rotational femoral osteotomies to increase FV are safe and effective.

Multivariate linear-mixed analysis of changes in anterior inferior iliac spine impingement incidence with posterior pelvic tilt: a computer simulation study

It is well known that increased posterior tilt of the pelvis is an effective strategy for avoiding impingement of the femur with the pelvis during movement. Daily repetitive collisions become mechanical loads, and the more frequently they occur, the more tissue damage and pain they cause. Therefore, reducing the rate of occurrence of impingement is important to avoid aggravation of symptoms. This study aimed to evaluate the effects of changes in posterior pelvic tilt on the risk of impingement between the femur and the anterior inferior iliac spine (AIIS)/subspine in various functional postures. Patients with femoroacetabular impingement syndrome (FAIS) who were candidates for hip arthroscopic osteochondroplasty between October 2013 and June 2020 were included. A three-dimensional reconstructed model was used to simulate the incidence of impingement at 12 hip positions required for activities of daily living. We predicted value of the spatial incidence of impingement assumed that hip motion should exceed 130/30 degrees without impingement. Impingement was measured at three pelvic positions: an anterior tilt of 10°, in the functional pelvic plane and a posterior tilt of 10°. Multivariate linear-mixed models were used to assess the effect of covariate-adjusted posterior pelvic tilt on the impingement incidence in the AIIS region. AIIS type, center-edge angle, acetabular version and femoral version were used as covariates. The impingement rates and locations of the three pelvic tilt postures were assessed. Seventy-eight patients (60 males and 18 females; average age, 46 ± 15.1 years) with FAIS were analyzed. A multivariate linear-mixed model revealed a coefficient of -0.8% (95% confidence interval -0.9 to -0.7%; P < 0.001) for posterior pelvic tilt. Thus, posterior pelvic tilt affects AIIS impingement incidence. After adjusting for anatomical effects, the posterior pelvic tilt should be addressed to avoid impingement.

Femoral anteversion linked to the inability to squat: Analysis of CT images in the patient and control groups

Many patients who cannot squat well in a neutral toe position can only squat in an excessively out-toeing position. This excessive out-toeing squat is thought to be caused by rotational problems of the lower extremities. In this study, we aimed to identify the cause for the inability to squat by measuring and comparing femoral and tibial torsion between an excessive out-toeing squat patient group and a control group representing the general population. Between 2008 and 2022, a patient group comprising 50 lower extremities with excessive out-toeing squats was established. A control group representing the general population was selected from patients aged 0 to 29 years, who underwent lower-extremity CT angiography between 2012 and 2022, using the Clinical Data Warehouse with exclusion criteria applied. A total of 94 lower extremities were included in the control group. The femoral torsional angle (FTA) and tibial torsional angle (TTA) of both groups were measured and compared using Student t test. Additionally, 30 each of those with the highest and lowest 30 FTA values were selected from the patient and control groups, and the TTA was compared between the high- and low-FTA groups using Student t test. The mean FTA was 0.34° (SD, 11.11°) in the patient group and 10.14° (SD, 11.85°) in the control group, with a mean difference of 9.8° and P < .001. The mean TTA was 27.95° (SD, 7.82°) in the patient group and 32.67 ° (SD, 7.58°) in the control group, with a mean difference of 4.72° (P = .001). The mean TTA was 34.3° (SD, 7.72°) in the high-FTA group and 28.17° (SD, 8.35°) in the low-FTA group, with a mean difference of 6.13° (P = .005). Patients with excessive out-toeing squat showed lower FTA and TTA values than the general population. Furthermore, although a correlation between FTA and TTA was not established through Pearson correlation analysis, a tendency was observed where a decrease in FTA was associated with a decrease in TTA. Based on these results, decreased FTA was demonstrated to be one of the major causes of excessive out-toeing squats.

Effect of Spinopelvic Parameters on Outcomes After Hip Arthroscopy for Femoroacetabular Impingement Syndrome

BACKGROUND

Spinopelvic parameters, including pelvic tilt (PT), sacral slope (SS), and pelvic incidence, have been developed to characterize the relationship between lumbar spine and hip motion, but a paucity of literature is available characterizing differences in spinopelvic parameters among patients with femoroacetabular impingement syndrome (FAIS) versus patients without FAIS, as well as the effect of these parameters on outcomes of arthroscopic treatment of FAIS.

PURPOSE

To (1) identify differences in spinopelvic parameters between patients with FAIS versus controls without FAIS; (2) identify associations between spinopelvic parameters and preoperative patient-reported outcomes (PROs); and (3) identify differences in PROs between patients with stiff spines (standing-sitting ΔSS ≤10°) versus those without.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

The study enrolled patients ≥18 years of age who underwent primary hip arthroscopy for treatment of FAIS with cam, pincer, or mixed (cam and pincer) morphology. Participants underwent preoperative standing-sitting imaging with a low-dose 3-dimensional radiography system and were matched on age and body mass index (BMI) to controls without FAIS who also underwent EOS imaging. Spinopelvic parameters measured on EOS films were compared between the FAIS and control groups. Patients with FAIS completed the modified Harris Hip Score (mHHS) and Non-Arthritic Hip Score (NAHS) before surgery and at 1-year follow-up. Outcome scores were compared between patients with stiff spines versus those without. Associations between spinopelvic parameters and baseline outcome scores were assessed with Pearson correlations. Continuous variables were compared with Student t test and/or Mann-Whitney U test, and categorical variables were compared with Fisher exact test.

RESULTS

A total of 50 patients with FAIS (26 men; 24 women; mean age, 36.1 ± 10.7 years; mean BMI, 25.6 ± 4.2) were matched to 30 controls without FAIS (13 men; 17 women; mean age, 36.6 ± 9.5 years; mean BMI, 26.7 ± 3.6). Age, sex, and BMI were not significantly different between the FAIS and control groups (P > .05). Standing PT was not significantly different between stiff and non-stiff cohorts (P = .73), but sitting PT in the FAIS group was more than double that of the control group (36.5° vs 15.0°; P < .001). Incidence of stiff spine was significantly higher in the FAIS group (62.0% vs 3.3%; P < .001). Among FAIS patients, those with stiff spines had a significantly higher prevalence of cam impingement, whereas those with non-stiff spines had a higher prevalence of mixed impingement (P = .04). No significant differences were seen in preoperative mHHS or NAHS scores or pre- to postoperative improvement in scores between FAIS patients with stiff spines versus those without (P > .05), but a greater sitting SS was found to be positively correlated with a higher baseline mHHS (r = 0.36; P = .02).

CONCLUSION

Patients with FAIS were more likely to have a stiff spine (standing-sitting ΔSS ≤10°) compared with control participants without FAIS. FAIS patients with stiff spines were more likely to have isolated cam morphology than patient without stiff spines. Although sitting SS was positively correlated with baseline mHHS, no significant differences were seen in 1-year postoperative outcomes between FAIS patients with versus without stiff spine.

Evaluating computed bony range of motion (BROM) by registering in-vitro cadaver-based functional range of motion (FROM) to a hip motion simulation

BACKGROUND

While modern hip replacement planning relies on hip motion simulation (HMS), it lacks the capability to include soft-tissues and ligaments restraints on computed bony range of motion (BROM), often leading to an overestimation of the in-vivo functional range of motion (FROM). Furthermore, there is a lack of literature on BROM assessment in relation to FROM. Therefore, the study aimed to assess computed BROM using in-vitro cadaver-derived FROM measurements, registered to a CT-based in-house HMS, and to further investigate the effect of functional and anatomical hip joint centres (FHJC and AHJC) on BROM.

METHOD

Seven limiting and three non-limiting circumducted passive FROM of four cadaver hips were measured using optical coordinate measuring machine with reference spheres (RSs) affixed to the pelvis and the femur, following CT-scan of the specimen. The RSs' centres were used to register the measured FROM in HMS, enabling its virtual recreation to compute corresponding BROM by detecting nearest bony impingement. FHJC, estimated from non-limiting FROM, was compared with AHJC to examine their positional differences and effect on BROM.

RESULTS

Differences in BROM and FROM were minimal in deep flexion (3.0° ± 4.1°) and maximum internal rotation (IR) at deep flexion (3.0° ± 2.9°), but substantially greater in extension (53.2° ± 9.5°). Bony impingement was observed during flexion, and IR at deep flexion for two hips. The average positional difference between FHJC and AHJC was 3.1 ± 1.2 mm, resulting in BROM differences of 1°-13° across four motions.

CONCLUSIONS

The study provided greater insight into the applicability and reliability of computed BROM in pre-surgical planning.

Development of a simulation system for femoroacetabular impingement detection based on 3D images

Image-based criteria have been adopted to diagnose femoroacetabular impingement (FAI). However, the overlapping property of the two-dimensional X-ray outlines and static and supine posture of taking computed tomography (CT) and magnetic resonance imaging images potentially affect the accuracy of the criteria. This study developed a CT image-based dynamic criterion to effectively simulate FAI, thereby providing a basis for physicians to perform pre-operative planning for arthroscopic surgery. Post-operative CT images of 20 patients with satisfactory surgical results were collected, and 10 sets of models were used to define the flexion rotation centre (FRC) of the three-dimensional FAI model. First, let these 10 groups of models simulate the FAI detection action and find the best centre offset, and then FRC is the result of averaging these 10 groups of best displacements. The model was validated in 10 additional patients. Finally, through the adjustment basis of FRC, the remaining 10 sets of models can find out the potential position of FAI during the dynamic simulation process. Rotational collisions detected using FRC indicate that the patient's post-operative flexion angle may reach 120° or greater, which is close to the actual result. The recommended surgical range of the diagnostic system (average length of 6.4 mm, width of 4.1 mm and depth of 3.2 mm) is smaller than the actual surgical results, which prevents the doctor from performing excessive resection operations, which may preserve more bones. The FRC diagnostic system detects the distribution of FAI in a simple manner. It can be used as a pre-operative diagnosis reference for clinicians, hoping to improve the effect and accuracy of debridement surgery.

[Femoroacetabular impingement in adolescents]

Femoroacetabular impingement syndrome (FAIS) is caused by a repetitive mechanical conflict between the acetabulum and the proximal femur, occurring in flexion and internal rotation. In cam impingement, bony prominences of the femoral head-neck junction induce chondrolabral damage. The acetabular type of FAIS, termed pincer FAIS, may be either due to focal or global retroversion and/or acetabular overcoverage. Combinations of cam and pincer morphology are common. Pathological femoral torsion may aggravate or decrease the mechanical conflict in FAI but can also occur in isolation. Of note, a high percentage of adolescents with FAI-like shape changes remain asymptomatic. The diagnosis of FAIS is therefore made clinically, whereas imaging reveals the underlying morphology. X‑rays in two planes remain the primary imaging modality, the exact evaluation of the osseous deformities of the femur and chondrolabral damage is assessed by magnetic resonance imaging (MRI). Acetabular coverage and version are primarily assessed on radiographs. Evaluation of the entire circumference of the proximal femur warrants MRI which is further used in the assessment of chondrolabral lesions, and also bone marrow and adjacent soft tissue abnormalities. The MRI protocol should routinely include measurements of femoral torsion. Fluid-sensitive sequences should be acquired to rule out degenerative or inflammatory extra-articular changes.

Feasibility of photon-counting CT for femoroacetabular impingement syndrome evaluation: lower radiation dose and improved diagnostic confidence

OBJECTIVE

The feasibility of low-dose photon-counting detector (PCD) CT to measure alpha and acetabular version angles of femoroacetabular impingement (FAI).

MATERIAL AND METHODS

FAI patients undergoing an energy-integrating detector (EID) CT underwent an IRB-approved prospective ultra-high-resolution (UHR) PCD-CT between 5/2021 and 12/2021. PCD-CT was dose-matched to the EID-CT or acquired at 50% dose. Simulated 50% dose EID-CT images were generated. Two radiologists evaluated randomized EID-CT and PCD-CT images and measured alpha and acetabular version angles on axial image slices. Image quality (noise, artifacts, and visualization of cortex) and confidence in non-FAI pathology were rated on a 4-point scale (3 = adequate). Preference tests of standard dose PCD-CT, 50% dose PCD-CT, and 50% dose EID-CT relative to standard dose EID-CT were performed using Wilcoxon Rank test.

RESULTS

20 patients underwent standard dose EID-CT (~ CTDIvol, 4.5 mGy); 10 patients, standard dose PCD-CT (4.0 mGy); 10 patients, 50% PCD-CT (2.6 mGy). Standard dose EID-CT images were scored as adequate for diagnostic task in all categories (range 2.8-3.0). Standard dose PCD-CT images scored higher than the reference in all categories (range 3.5-4, p < 0.0033). Half-dose PCD-CT images also scored higher for noise and cortex visualization (p < 0.0033) and equivalent for artifacts and visualization of non-FAI pathology. Finally, simulated 50% EID-CT images scored lower in all categories (range 1.8-2.4, p < 0.0033).

CONCLUSIONS

Dose-matched PCD-CT is superior to EID-CT for alpha angle and acetabular version measurement in the work up of FAI. UHR-PCD-CT enables 50% radiation dose reduction compared to EID while remaining adequate for the imaging task.

Effect of Differing Orientation and Magnitude of Femoral Torsion on Outcomes and Achievement of the MCID and PASS at 5 Years After Hip Arthroscopy for Femoroacetabular Impingement Syndrome

BACKGROUND

Femoral torsion measurements and outcomes are variable throughout the literature and have focused on short-term follow-up. However, there is a paucity of literature investigating clinically meaningful outcomes at midterm follow-up after hip arthroscopy for femoroacetabular impingement syndrome (FAIS).

PURPOSE

To quantify femoral version using computed tomography imaging in patients with FAIS and to explore the relationship between version abnormalities and 5-year outcomes after hip arthroscopy.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

Patients who underwent primary hip arthroscopy for FAIS between January 2012 and November 2017 were identified. Patients were included if they had 5-year follow-up with completion of ≥1 patient-reported outcome (PRO) scores and excluded if they had Tönnis grade >1, revision hip surgery, a concomitant hip procedure, a developmental disorder, or a lateral center-edge angle <20°. Torsion groups were defined as severe retrotorsion (<0°), moderate retrotorsion (0.1°-5°), normal torsion (5.1°-20°), moderate antetorsion (20.1°-25°), and severe antetorsion (>25.1°) based on computed tomography measurements. Patient characteristics were analyzed among the torsion cohorts, as were preoperative and 5-year PROs: Hip Outcome Score-Activities of Daily Living, Hip Outcome Score-Sports Subscale, modified Harris Hip Score, international Hip Outcome Tool, visual analog scale for pain, and visual analog scale for satisfaction. Achievement rates of cohort-specific thresholds for the minimal clinically important difference and Patient Acceptable Symptom State were calculated and compared among cohorts.

RESULTS

A total of 362 patients (244 female, 118 male; mean ± SD age, 33.1 ± 11.5 years; body mass index, 26.9 ± 17.8) met inclusion/exclusion criteria and were analyzed at a final mean follow-up of 64.3 ± 9.4 months (range, 53.5-115.5 months). Mean femoral torsion was 12.8°± 9.2°. The number of patients within each group was 20 for severe retrotorsion (torsion, -6.3°± 4.9°), 45 for moderate retrotorsion (2.7°± 1.3°), 219 for normal torsion (12.2°± 4.1°), 39 for moderate antetorsion (21.9°± 1.3°), and 39 for severe antetorsion (29.0°± 4.2°). No significant differences in age, body mass index, sex, smoking status, workers' compensation, psychiatric history, back pain, or physical activity were found among the torsional groups. All groups demonstrated significant improvements at 5 years postoperatively (P < .01 for all). All torsion subgroups demonstrated similar pre- to postoperative changes in PROs (P≥ .515) and PRO values at 5-year follow-up (P≥ .098). There were no significant differences in the achievement of the minimal clinically important difference (P≥ .422) or Patient Acceptable Symptom State (P≥ .161) for any of the PROs among the torsion groups.

CONCLUSION

The orientation and severity of femoral torsion at the time of hip arthroscopy for FAIS in this study's cohort did not affect the propensity for clinically meaningful outcome improvement at midterm follow-up.

Can a Computational Model Predict the Effect of Lesion Location on Cam-type Hip Impingement?

BACKGROUND

The Warwick consensus defined femoroacetabular impingement syndrome as a motion-related clinical disorder of the hip with a triad of symptoms, clinical signs, and imaging findings representing symptomatic premature contact between the proximal femur and acetabulum. Several factors appear to cause labral and cartilage damage, including joint shape and orientation and patient activities. There is a lack of tools to predict impingement patterns in a patient across activities. Current computational modeling tools either measure pure ROM of the joint or include complexity that reduces reliability and increases time to achieve a solution.

QUESTIONS/PURPOSES

The purpose of this study was to examine the efficacy of a low computational cost approach to combining cam-type hip shape and multiple hip motions for predicting impingement. Specifically, we sought to determine (1) the potential to distinguish impingement in individual hip shapes by analyzing the difference between a cam lesion at the anterior femoral neck and one located at the superior femoral neck; (2) sensitivity to three aspects of hip alignment, namely femoral neck-shaft angle, femoral version angle, and pelvic tilt; and (3) the difference in impingement measures between the individual activities in our hip motion dataset.

METHODS

A model of the shape and alignment of a cam-type impinging hip was created and used to describe two locations of a cam lesion on the femoral head-neck junction (superior and anterior) based on joint shape information available in prior studies. Sensitivity to hip alignment was assessed by varying three aspects from a baseline (typical alignment described in prior studies), namely, femoral neck-shaft angle, femoral version, and pelvic tilt. Hip movements were selected from an existing database of 18 volunteers performing 13 activities (10 male, eight female; mean age 44 ± 19 years). A subset was selected to maximize variation in the range of joint angles and maintain a consistent number of people performing each activity, which resulted in nine people per activity, including at least three of each sex. Activities included pivoting during walking, squatting, and golf swing. All selected hip motion cases were applied to each hip shape model. For the first part of the study, the number of motion cases in which impingement was predicted was recorded. Quantitative analyses of the depth of penetration of the cam lesion into the acetabular socket and qualitative observations of impingement location were made for each lesion location (anterior and superior). In the second part of the study, in which we aimed to test the sensitivity of the findings to hip joint orientation, full analysis of both cam lesion locations was repeated for three modified joint orientations. Finally, the results from the first part of the analysis were divided by activity to understand how the composition of the activity dataset affected the results.

RESULTS

The two locations of cam lesion generated impingement in a different percentage of motion cases (anterior cam: 56% of motion cases; superior cam: 13% of motion cases) and different areas of impingement in the acetabulum, but there were qualitatively similar penetration depths (anterior cam: 6.8° ± 5.4°; superior cam: 7.9° ± 5.8°). The most substantial effects of changing the joint orientation were a lower femoral version angle for the anterior cam, which increased the percentage of motion cases generating impingement to 67%, and lower neck-shaft angle for the superior cam, which increased the percentage of motion cases generating impingement to 37%. Flexion-dominated activities (for example, squatting) only generated impingement with the anterior cam. The superior cam generated impingement during activities with high internal-external rotation of the joint (for example, the golf swing).

CONCLUSION

This work demonstrated the capability of a simple, rapid computational tool to assess impingement of a specific cam-type hip shape (under 5 minutes for more than 100 motion cases). To our knowledge, this study is the first to do so for a large set of motion cases representing a range of activities affecting the hip, and could be used in planning surgical bone removal.

CLINICAL RELEVANCE

The results of this study imply that patients with femoroacetabular impingement syndrome with cam lesions on the superior femoral head-neck junction may experience impinging during motions that are not strongly represented by current physical diagnostic tests. The use of this tool for surgical planning will require streamlined patient-specific hip shape extraction from imaging, model sensitivity testing, evaluation of the hip activity database, and validation of impingement predictions at an individual patient level.

Outcomes of percutaneous femoral derotational osteotomy in pediatric patients

Background

Percutaneous femoral derotational osteotomies are performed in both adult and pediatric patients. There is little published on the outcomes after femoral derotational osteotomy in pediatric patients.

Methods

A retrospective cohort study of pediatric patients treated with percutaneous femoral derotational osteotomy by one of two surgeons between 2016 and 2022 was performed. Data collected included patient demographics; surgical indications; femoral version; tibial torsion; magnitude of rotational correction; complications; time to hardware removal; pre-operative and post-operative patient-reported outcome scores, including Limb Deformity-Scoliosis Research Society and Patient-Reported Outcomes Measurement Information System; and time to consolidation. Descriptive statistics were used to summarize the data and t tests used to compare means.

Results

Thirty-one femoral derotational osteotomies in 19 patients were included with an average age of 14.7 (9-17) years. The average rotational correction was 21.5° ± 6.4° (10°-40°). The average length of follow-up was 17.9 ± 6.7 months. There were no instances of nonunion, joint stiffness, or nerve injury. No patients returned to the operating room for additional surgeries other than routine hardware removal. There were no cases of avascular necrosis of the femoral head. Of the 19 patients, 8 completed both a pre-operative and post-operative survey set. There were significant improvements in the Limb Deformity-Scoliosis Research Society Self-Image/Appearance sub-category and the Patient-Reported Outcomes Measurement Information System Physical Function sub-category.

Conclusion

Femoral derotational osteotomy using a percutaneous drill hole technique with antegrade trochanteric entry femoral nail is safe in the pediatric population and improves self-image in patients with symptomatic femoral version abnormalities.

Arthroscopic Decompression of the Anterior Inferior Iliac Spine

Background

Pathologic contact between the femoral neck and anterior inferior iliac spine (AIIS or subspine) often occurs concomitantly with femoroacetabular impingement, contributing to hip pain and dysfunction1-4. We perform arthroscopic AIIS decompression to alleviate this source of extra-articular impingement and eliminate a potential cause of persistent pain following primary hip arthroscopy5-7.

Description

After identifying abnormal AIIS morphology on preoperative false-profile radiographs and/or 3D computed tomography, we utilize a beaver blade to make a small incision in the proximal capsule and rectus femoris tendon. This peri-capsulotomy window grants access to the subspine region. We then shuttle an arthroscopic burr into place within this window and begin debriding the subspine deformity under direct visualization. Fluoroscopy is utilized intraoperatively to ensure adequate resection, using intraoperative false-profile views achieved by canting the C-arm approximately 40°. Resection is considered adequate when the AIIS deformity is no longer readily apparent on false-profile views and when intraoperative range-of-motion testing confirms no further impingement with hip hyperflexion.

Alternatives

Femoroacetabular impingement can be treated nonoperatively with use of physical therapy and activity modification8; however, outcomes following nonoperative treatment are inferior to those following hip arthroscopy, according to various studies9-12. There are no known alternative treatments specific to subspine impingement.

Rationale

As patients with subspine deformities progress through hip flexion, the femoral neck collides with the AIIS, limiting range of motion. As such, subspine deformities have been shown to be more common in dancers and other high-flexion athletes13,14. Additionally, studies have demonstrated that low femoral version of <5° is associated with increased contact between the distal femoral neck and the AIIS. This pathologic contact can occur even in the absence of an obvious subspine deformity15. In both of these patient populations, surgeons should have a high suspicion for subspine impingement, and a subspine decompression should be performed during hip arthroscopy in order to maximize patient outcomes.

Expected Outcomes

This is a safe procedure that, if performed when indicated, can improve outcomes following primary hip arthroscopy. A recent systematic review found a pooled complication risk of 1.1%, a pooled revision risk of 1.0%, and significant postoperative improvements in patient-reported outcome measures16.

Important Tips

Suspect subspine impingement in high-flexion athletes and patients with low femoral version, even in the absence of an obvious deformity.Ensure adequate visualization of the entire subspine deformity by creating a pericapsular window.Confirm thorough resection with use of fluoroscopic imaging intraoperatively, including false-profile views demonstrating absent subspine deformity.

Acronyms and Abbreviations

FAI = femoroacetabular impingementAP = anteroposterior, refers to the technique used to obtain one of the pelvic radiographs3D CT = three-dimensional computed tomographyLCEA = lateral center-edge angle, a measurement used to quantify severity of hip dysplasiaOR = operating roomAlpha = alpha angle, a measurement used to measure femoral head-neck offset and assess the severity of a cam deformityIc = iliocapsularisRFd = direct head of rectus femorisRFr = reflected head of rectus femorisCap = hip capsuleGMi = gluteus minimusmHHS = modified Harris Hip ScoreHOS-ADL = Hip Outcome Score - Activities of Daily LivingHOS-SSS = Hip Outcome Score - Sports Specific Subscale.

Assessment of femoral retroversion on preoperative hip magnetic resonance imaging in patients with slipped capital femoral epiphysis: Theoretical implications for hip impingement risk estimation

Purpose

Slipped capital femoral epiphysis is a common pediatric hip disease and was associated with femoral retroversion, but femoral version was rarely measured. Therefore, mean femoral version, mean femoral neck version, and prevalence of femoral retroversion were analyzed for slipped capital femoral epiphysis patients.

Methods

A retrospective observational study evaluating preoperative hip magnetic resonance imaging of 27 patients (49 hips) was performed. Twenty-seven untreated slipped capital femoral epiphysis patients (28 slipped capital femoral epiphysis hips and 21 contralateral hips, age 10-16 years) were evaluated (79% stable slipped capital femoral epiphysis, 22 patients; 43% severe slipped capital femoral epiphysis, 12 patients). Femoral version was measured using Murphy method on magnetic resonance imaging (January 2014-December 2021, rapid bilateral 3-dimensional T1 water-only Dixon-based images of pelvis and knee). All slipped capital femoral epiphysis patients underwent surgery after magnetic resonance imaging.

Results

Mean femoral version of slipped capital femoral epiphysis patients (-1° ± 15°) was significantly (p < 0.001) lower compared to contralateral side (15° ± 14°). Femoral version of slipped capital femoral epiphysis patients had significantly (p < 0.001) wider range from -42° to 35° (range 77°) compared to contralateral side (-5° to 44°, range 49°). Mean femoral neck version of slipped capital femoral epiphysis patients (6° ± 15°) was lower compared to contralateral side (11° ± 12°). Fifteen slipped capital femoral epiphysis patients (54%) had absolute femoral retroversion (femoral version < 0°). Six of the 12 hips (50%) with severe slips and 4 of the 8 hips (50%) with mild slips had absolute femoral retroversion (femoral version < 0°). Ten slipped capital femoral epiphysis patients (40%) had absolute femoral neck retroversion (femoral neck version < 0°).

Conclusion

Although slipped capital femoral epiphysis patients showed asymmetrically lower femoral version compared to contralateral side, there was a wide range of femoral version, underlining the importance of patient-specific femoral version analysis on preoperative magnetic resonance imaging. Absolute femoral retroversion was prevalent in half of slipped capital femoral epiphysis patients, in half of severe slipped capital femoral epiphysis patients, and in half of mild slipped capital femoral epiphysis patients. This has implications for anterior hip impingement and for surgical treatment with in situ pinning or femoral osteotomy (e.g. proximal femoral derotation osteotomy) or other hip preservation surgery.

Sex differences in the anatomy of the anterior-superior acetabular rim in relation to pincer-type femoroacetabular impingement in Koreans: a three-dimensional quantitative analysis

PURPOSE

The aim of this study was to compare the anatomical structures of the acetabular rim around the anterior inferior iliac spine (AIIS) ridge that indicate anterior focal coverage of acetabulum between the sexes using a three-dimensional (3D) model.

METHODS

3D models of 71 adults (38 men and 33 women) with normal hip joints were used. Based on the location of the inflection point (IP) of the acetabular rim around the AIIS ridge, the patients were classified into anterior and posterior types, and the ratios thereof for each sex were compared. Coordinates for the IP, the most anterior point (MAP), and the most lateral point (MLP) were obtained and compared between the sexes and between anterior and posterior types.

RESULTS

Coordinates for IPs in men were located anterior and inferior to those in women. MAP coordinates for men were located inferior to those for women, and MLP coordinates for men were located lateral and inferior to those for women. Comparing AIIS ridge types, we noted that coordinates for IPs of the anterior type were located medial, anterior, and inferior to those of the posterior type. Meanwhile, MAP coordinates of the anterior type were located inferior to those of the posterior type, and MLP coordinates of the anterior type were located lateral and inferior to those of the posterior type.

CONCLUSION

Anterior focal coverage of the acetabulum appears to differ between the sexes, and this difference may affect the development of pincer-type femoroacetabular impingement (FAI). Additionally, we found that anterior focal coverage differs according to anterior or posterior positioning of the bony prominence around the AIIS ridge, which may affect development of FAI.

Outcomes of Arthroscopic Decompression of the Anterior Inferior Iliac Spine: A Systematic Review and Meta-analysis

BACKGROUND

Anterior inferior iliac spine (AIIS) impingement has been increasingly recognized as a source of extra-articular impingement and hip pain. However, no aggregate data analysis of patient outcomes after AIIS decompression has been performed.

PURPOSE

To evaluate outcomes after arthroscopic AIIS decompression.

STUDY DESIGN

Meta-analysis; Level of evidence, 4.

METHODS

A systematic review was performed according to the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. PubMed, EMBASE, and Cochrane Central Register of Controlled Trials were queried for all English-language studies reporting outcomes of arthroscopic AIIS decompression performed in isolation or in conjunction with hip impingement correction surgery. After screening, 10 articles were included. The indications for AIIS decompression were recorded, and weighted mean improvements in patient-reported outcome (PRO) scores, complication rates, and revision rates were calculated.

RESULTS

A total of 547 patients (311 women; 57%) were identified, with a total of 620 operative hips. The mean age was 28.42 ± 5.6 years, and the mean follow-up was 25.22 ± 11.1 months. A total of 529 hips (85%) underwent AIIS decompression, 530 hips (85%) underwent femoral osteochondroplasty, and 458 hips (74%) underwent labral repair. Of the patients, 13% underwent bilateral AIIS decompression. The mean modified Harris Hip Score improved from 61.3 ± 6.9 to 88.7 ± 4.7 postoperatively (change, 27.4 ± 5.7 points; P < .001), the Hip Outcome Score-Activities of Daily Living improved from 67.2 ± 10.6 to 91.1 ± 3.2 postoperatively (change, 24.0 ± 8.0 points; P = .001), and the Hip Outcome Score-Sports Specific Subscale improved from 36.8 ± 19.2 to 82.8 ± 3.8 postoperatively (change, 46.0 ± 18.2 points; P = .002). The pooled risk of postoperative complications was 1.1% (95% CI, 0.1%-2.1%), and the pooled risk of needing revision surgery was 1.0% (95% CI, 0.1%-2.0%). No complication was directly attributed to the AIIS decompression portion of the procedure.

CONCLUSION

PROs improved significantly after hip arthroscopy with AIIS decompression, with a low risk of postoperative complications and subsequent revision surgeries. Failure to identify extra-articular sources of hip pain in outcomes of femoroacetabular impingement syndrome, including from the AIIS, could lead to poorer outcomes and future revision surgery.

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°, <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.

Subspine femoroacetabular impingement: retrospective study of a series of patients treated by hip arthroscopic resection

BACKGROUND

Femoroacetabular impingement syndrome (FAIS) is a common hip pathology that causes pain and functional limitation in young patients. subspine femoroacetabular impingement (SFAI) is an increasingly diagnosed extra-articular subtype that occurs from mechanical conflict of the anteroinferior iliac spine (AIIS) with the cervico-diaphyseal junction during hip flexion, which is poorly described in the literature.

QUESTIONS/PURPOSES

We aimed to describe the clinical, functional, and radiological results of the arthroscopic treatment of a group of patients with SFAI treated in our Hip Unit.

STUDY DESIGN

Case series.

METHODS

We present a retrospective study of ten patients with SFAI treated between 2013 and 2020 with arthroscopic resection. Clinical results were assessed with scales such as visual analog scale (VAS); modified Harris Hip Score (mHHS), and Hip disability and Osteoarthritis Outcome Score (HOOS). Radiological results were assessed with radiological measurements, magnetic resonance imaging (MRI), and computed tomography (CT) reconstructions.

RESULTS

Six patients had a Type III AIIS and four of them had Type II. Two patients had previously been surgically treated for FAIS. The range of motion improved in flexion from 107 ± 11 degrees before surgery to 127.5 ± 6 degrees (p = 0.005). MHHS improved from 48.1 (38-75.3) before surgery to 83.1 (57-91) (p = 0.007) and HOOS improved from 65.2 (58-75) to 89 (68.1-100) (p = 0.007). VAS improved from 7.3 (5-9) pre-surgical to 2.5 (0-8) post-surgical (p = 0.005). We did not have significant complications except for an asymptomatic case of heterotopic ossification (Brooker I).

CONCLUSION

Arthroscopic decompression of AIIS in SFAI patients is a safe procedure that provides satisfactory short-term functional results, improving clinical symptoms, function, sports performance, and range of motion in our study.

Do patients with femoroacetabular impingement syndrome who undergo hip arthroscopy display improved alpha angle (magnetic resonance imaging) and radiographic hip morphology?

AIMS

To compare (a) the change in radiological bony morphology between participants with femoroacetabular impingement (FAI) syndrome who underwent arthroscopic hip surgery compared to physiotherapist-led non-surgical care and (b) the change in radiological bony morphology between participants with FAI syndrome who underwent arthroscopic hip surgery involving cam resection or acetabular rim trimming or combined cam resection and acetabular rim trimming.

METHODS

Maximum alpha angle measurements on magnetic resonance imaging and Hip2 Norm standardized hip measurements on radiographs were recorded at baseline and at 12 months postoperatively. One-way analysis of covariance and independent T tests were conducted between participants who underwent arthroscopic hip surgery and physiotherapist-led non-surgical care. Independent T tests and analysis of variance were conducted between participants who underwent the 3 different arthroscopic hip procedures.

RESULTS

Arthroscopic hip surgery resulted in significant improvements to mean alpha angle measurements (decreased from 70.8° to 62.1°) (P value < .001, 95% CI -11.776, -4.772), lateral center edge angle (LCEA) (P value = .030, 95% CI -3.403, -0.180) and extrusion index (P value = 0.002, 95% CI 0.882, 3.968) compared to physiotherapist-led management. Mean maximum 1-year postoperative alpha angle was 59.0° (P value = .003, 95% CI 4.845, 18.768) for participants who underwent isolated cam resection. Measurements comparing the 3 different arthroscopic hip procedures only differed in total femoral head coverage (F[2,37] = 3.470, P = .042).

CONCLUSION

Arthroscopic hip surgery resulted in statistically significant improvements to LCEA, extrusion index and alpha angle as compared to physiotherapist-led management. Measured outcomes between participants who underwent cam resection and/or acetabular rim trimming only differed in total femoral head coverage.

Femoral impingement in maximal hip flexion is anterior-inferior distal to the cam deformity in femoroacetabular impingement patients with femoral retroversion : implications for hip arthroscopy

AIMS

Femoroacetabular impingement (FAI) patients report exacerbation of hip pain in deep flexion. However, the exact impingement location in deep flexion is unknown. The aim was to investigate impingement-free maximal flexion, impingement location, and if cam deformity causes hip impingement in flexion in FAI patients.

METHODS

A retrospective study involving 24 patients (37 hips) with FAI and femoral retroversion (femoral version (FV) < 5° per Murphy method) was performed. All patients were symptomatic (mean age 28 years (SD 9)) and had anterior hip/groin pain and a positive anterior impingement test. Cam- and pincer-type subgroups were analyzed. Patients were compared to an asymptomatic control group (26 hips). All patients underwent pelvic CT scans to generate personalized CT-based 3D models and validated software for patient-specific impingement simulation (equidistant method).

RESULTS

Mean impingement-free flexion of patients with mixed-type FAI (110° (SD 8°)) and patients with pincer-type FAI (112° (SD 8°)) was significantly (p < 0.001) lower compared to the control group (125° (SD 13°)). The frequency of extra-articular subspine impingement was significantly (p < 0.001) increased in patients with pincer-type FAI (57%) compared to cam-type FAI (22%) in 125° flexion. Bony impingement in maximal flexion was located anterior-inferior at femoral four and five o'clock position in patients with cam-type FAI (63% (10 of 16 hips) and 37% (6 of 10 hips)), and did not involve the cam deformity. The cam deformity did not cause impingement in maximal flexion.

CONCLUSION

Femoral impingement in maximal flexion was located anterior-inferior distal to the cam deformity. This differs to previous studies, a finding which could be important for FAI patients in order to avoid exacerbation of hip pain in deep flexion (e.g. during squats) and for hip arthroscopy (hip-preservation surgery) for planning of bone resection. Hip impingement in flexion has implications for daily activities (e.g. putting on shoes), sports, and sex.Cite this article: Bone Joint Res 2023;12(1):22-32.

Combined femoral and acetabular version is sex-related and differs between patients with hip dysplasia and acetabular retroversion

AIMS

Frequency of abnormal femoral and acetabular version (AV) and combinations are unclear in patients with developmental dysplasia of the hip (DDH). This study aimed to investigate femoral version (FV), the proportion of increased FV and femoral retroversion, and combined-version (CV, FV+AV) in DDH patients and acetabular-retroversion (AR).

PATIENTS AND METHODS

A retrospective IRB-approved observational study was performed with 78 symptomatic DDH patients (90 hips) and 65 patients with femoroacetabular-impingement (FAI) due to AR (77 hips, diagnosis on AP radiographs). CT/MRI-based measurement of FV (Murphy method) and central AV were compared. Frequency of increased FV(FV > 25°), severely increased FV (FV > 35°) and excessive FV (FV > 45°) and of decreased FV (FV < 10°) and CV (McKibbin-index/COTAV-index) was analysed.

RESULTS

Mean FV and CV was significantly (p < 0.001) increased of DDH patients (mean ± SD of 25 ± 11° and 47 ± 18°) compared to AR (16 ± 11° and 28 ± 13°). Mean FV of female DDH patients (27 ± 16°) and AR (19 ± 12°) was significantly (p < 0.001) increased compared to male DDH patients (18 ± 13°) and AR (13 ± 8°). Frequency of increased FV (>25°) was 47% and of severely increased FV (>35°) was 23% for DDH patients. Proportion of femoral retroversion (FV < 10°) was significantly (p < 0.001) higher in patients AR (31%) compared to DDH patients (17%). 18% of DDH patients had AV > 25° combined with FV > 25°. Of patients with AR, 12% had FV < 10° combined with AV < 10°.

CONCLUSION

Patients with DDH and AR have remarkable sex-related differences of FV and CV. Frequency of severely increased FV > 35° (23%) is considerable for patients with DDH, but 17% exhibited decreased FV, that could influence management. The different combinations underline the importance of patient-specific evaluation before open hip preservation surgery (periacetabular osteotomy and femoral derotation osteotomy) and hip-arthroscopy.

Open and arthroscopic management of femoroacetabular impingement: a review of current concepts

Femoroacetabular impingement (FAI) is a common femoral and/or acetabular abnormality that can cause progressive damage to the hip and osteoarthritis. FAI can be the result of femoral head/neck overgrowth, acetabular overgrowth or both femoral and acetabular abnormalities, resulting in a loss of native hip biomechanics and pain upon hip flexion and rotation. Radiographic evidence can include loss of sphericity of the femoral neck (cam impingement) and/or acetabular retroversion with focal or global overcoverage (pincer impingement). Operative intervention is indicated in symptomatic patients after failed conservative management with radiographic evidence of impingement and minimal arthritic changes of the hip, with the goal of restoring normal hip biomechanics and reducing pain. This is done by correcting the femoral head-neck relationship to the acetabulum through femoral and/or acetabular osteoplasty and treatment of concomitant hip pathology. In pincer impingement cases with small lunate surfaces, reverse periacetabular osteotomy is indicated as acetabular osteoplasty can decrease an already small articular surface. While surgical dislocation is regarded as the traditional gold standard, hip arthroscopy has become widely utilized in recent years. Studies comparing both open surgery and arthroscopy have shown comparable long-term pain reduction and improvements in clinical measures of hip function, as well as similar conversion rates to total hip arthroplasty. However, arthroscopy has trended toward earlier improvement, quicker recovery and faster return to sports. The purpose of this study was to review the recent literature on open and arthroscopic management of FAI.

Limited Hip Flexion and Internal Rotation Resulting From Early Hip Impingement Conflict on Anterior Metaphysis of Patients With Untreated Severe SCFE Using 3D Modelling

INTRODUCTION

Slipped capital femoral epiphysis (SCFE) is the most common hip disorder in adolescent patients that can result in complex 3 dimensional (3D)-deformity and hip preservation surgery (eg, in situ pinning or proximal femoral osteotomy) is often performed. But there is little information about location of impingement.Purpose/Questions: The purpose of this study was to evaluate (1) impingement-free hip flexion and internal rotation (IR), (2) frequency of impingement in early flexion (30 to 60 degrees), and (3) location of acetabular and femoral impingement in IR in 90 degrees of flexion (IRF-90 degrees) and in maximal flexion for patients with untreated severe SCFE using preoperative 3D-computed tomography (CT) for impingement simulation.

METHODS

A retrospective study involving 3D-CT scans of 18 patients (21 hips) with untreated severe SCFE (slip angle>60 degrees) was performed. Preoperative CT scans were used for bone segmentation of preoperative patient-specific 3D models. Three patients (15%) had bilateral SCFE. Mean age was 13±2 (10 to 16) years and 67% were male patients (86% unstable slip, 81% chronic slip). The contralateral hips of 15 patients with unilateral SCFE were evaluated (control group). Validated software was used for 3D impingement simulation (equidistant method).

RESULTS

(1) Impingement-free flexion (46±32 degrees) and IRF-90 degrees (-17±18 degrees) were significantly ( P <0.001) decreased in untreated severe SCFE patients compared with contralateral side (122±9 and 36±11 degrees).(2) Frequency of impingement was significantly ( P <0.001) higher in 30 and 60 degrees flexion (48% and 71%) of patients with severe SCFE compared with control group (0%).(3) Acetabular impingement conflict was located anterior-superior (SCFE patients), mostly 12 o'clock (50%) in IRF-90 degrees (70% on 2 o'clock for maximal flexion). Femoral impingement was located on anterior-superior to anterior-inferior femoral metaphysis (between 2 and 6 o'clock, 40% on 3 o'clock and 40% on 5 o'clock) in IRF-90 degrees and on anterior metaphysis (40% on 3 o'clock) in maximal flexion and frequency was significantly ( P <0.001) different compared with control group.

CONCLUSION

Severe SCFE patients have limited hip flexion and IR due to early hip impingement using patient-specific preoperative 3D models. Because of the large variety of hip motion, individual evaluation is recommended to plan the osseous correction for severe SCFE patients.

LEVEL OF EVIDENCE

Level III.

Arthroscopic Femoral and Acetabular Osteoplasties Alter the In Vivo Hip Kinematics of Patients With Femoroacetabular Impingement

Purpose

Three-dimensional (3D)-two-dimensional (2D) fluoroscopic image registration was used to measure 3D hip kinematics before and after hip arthroscopy in patients with femoroacetabular impingement (FAI).

Methods

In total, 24 subjects diagnosed with FAI (21 unilateral, 3 bilateral) were prospectively recruited. A clinical impingement test was performed on both hips while the patient was awake and then while anaesthetized, and in the operative hip after arthroscopic osteoplasties and labral repair. Fluoroscopy was used to image the hip during the impingement tests. Images were analyzed using 3D-2D image registration to calculate joint kinematics. The examiner's hand was instrumented with a glove to measure internal rotation torque applied to the hip during each test.

Results

Internal rotation increased by 3.7° (standard error [SE] 0.95°) after surgery (P = .001). Maximum displacement of the femoral head out of the acetabulum was 4.0 mm (SE 0.5 mm) in the operative group before surgery and 1.8 mm (SE 0.3 mm) after surgery (P < .001). This was due to a decrease in lateral displacement by 1.3 mm (SE 0.4 mm, P = .002) and proximal displacement by 0.8 mm (SE 0.3 mm, P = .013). Internal rotation torque was greater in the operative hips when anaesthetized compared with when awake, by 5 Nm (SE 1.2 Nm, P < .001), and greater in the contralateral hips than the operative hips when awake by 8.4 Nm (SE 1.4 mm, P < .001).

Conclusions

Arthroscopic osteoplasty and labral repair increased hip range of motion and reduced femoral head displacement from the acetabulum during the IR90 provocation test (i.e., hip flexion to 90°, maximum internal rotation) in patients with FAI. This suggests that the impinging acetabular rim acted as a fulcrum before surgery and may have caused edge loading that was reduced after surgery.

Level of Evidence

Level IV case series, therapeutic study.

Coxa valga and antetorta increases differences among different femoral version measurements

Aims

To evaluate how abnormal proximal femoral anatomy affects different femoral version measurements in young patients with hip pain.

Methods

First, femoral version was measured in 50 hips of symptomatic consecutively selected patients with hip pain (mean age 20 years (SD 6), 60% (n = 25) females) on preoperative CT scans using different measurement methods: Lee et al, Reikerås et al, Tomczak et al, and Murphy et al. Neck-shaft angle (NSA) and α angle were measured on coronal and radial CT images. Second, CT scans from three patients with femoral retroversion, normal femoral version, and anteversion were used to create 3D femur models, which were manipulated to generate models with different NSAs and different cam lesions, resulting in eight models per patient. Femoral version measurements were repeated on manipulated femora.

Results

Comparing the different measurement methods for femoral version resulted in a maximum mean difference of 18° (95% CI 16 to 20) between the most proximal (Lee et al) and most distal (Murphy et al) methods. Higher differences in proximal and distal femoral version measurement techniques were seen in femora with greater femoral version (r > 0.46; p < 0.001) and greater NSA (r > 0.37; p = 0.008) between all measurement methods. In the parametric 3D manipulation analysis, differences in femoral version increased 11° and 9° in patients with high and normal femoral version, respectively, with increasing NSA (110° to 150°).

Conclusion

Measurement of femoral version angles differ depending on the method used to almost 20°, which is in the range of the aimed surgical correction in derotational femoral osteotomy and thus can be considered clinically relevant. Differences between proximal and distal measurement methods further increase by increasing femoral version and NSA. Measurement methods that take the entire proximal femur into account by using distal landmarks may produce more sensitive measurements of these differences.

Cite this article: Bone Jt Open 2022;3(10):759–766.

Percutaneous Femoral Derotational Osteotomy in the Skeletally Immature Patient

Percutaneous femoral derotational osteotomies are performed in both adult and pediatric patients for excessive symptomatic femoral anteversion or retroversion^1,2. The aim of the procedure is to correct version abnormalities with use of a minimally invasive technique³.

Description

This is a percutaneous procedure that involves creation of femoral drill holes at the osteotomy site prior to reaming the canal⁴. External fixator pins are placed proximal and distal to the osteotomy site prior to completing the osteotomy. These pins are derotational markers for the surgeon and act to hold the correction with use of an external fixator while the interlocking screws are being placed. The pins are placed at a degree of divergence that is equal to the degree of intended derotation so that the pins will become parallel in the axial plane following derotation of the femur. The percutaneous osteotomy is then completed with use of an osteotome, and the trochanteric entry nail is passed across the osteotomy site while correcting rotation. Once rotation is fully corrected and the pins are parallel, the external fixator is placed to hold the rotation and interlocking screws are placed.

Alternatives

Nonoperative alternatives to this procedure include physical therapy for gait training and strengthening as well as modalities to address hip and knee pain that may be associated with version abnormalities. Although physical therapy is often prescribed, it must be noted that excess version is a fixed osseous structural pathology that therapy cannot address. Additionally, compensatory mechanisms that may be taught to improve gait and walk with a neutral foot progression angle may exacerbate hip or knee pathology as a result of the underlying version abnormality. Surgical alternatives include derotational osteotomies of the proximal or distal aspects of the femur with use of an open technique with plate fixation, as opposed to an intramedullary nail following percutaneous diaphyseal osteotomy as presented here¹. Additionally, an open technique with intramedullary nail fixation may be performed⁵.

Rationale

Excessive anteversion can cause both hip and knee symptoms, including hip pain, instability, labral and psoas pathology, and patellofemoral instability⁶. Excessive retroversion can cause impingement between the femoral neck and acetabulum, which results in pathology of the labrum and articular cartilage⁷. Additionally, abnormalities of version often lead to gait disturbances with frequent tripping and difficulty running⁸. Children with femoral version abnormalities have limited remodeling potential after age 8³. A derotational osteotomy may be performed to correct symptomatic excess femoral version in an older child or adolescent.

Expected Outcomes

The patient may be weight-bearing as tolerated with upper-extremity assistance immediately following the procedure. The osteotomy typically heals between 6 and 12 weeks, and the patient may return to activities as tolerated once the osteotomy is healed. Gordon et al. described the outcomes of a similar technique for femoral derotational osteotomy in skeletally immature patients with excessive femoral anteversion³. The study retrospectively reviewed the results of the technique in 13 patients and 21 limbs at a minimum follow-up of 1 year. All patients complained of tripping and gait abnormalities preoperatively. All patients noted gait improvement, and no intraoperative or postoperative complications were reported. Healing of the osteotomy occurred at a mean of 6 weeks postoperatively. No patient developed osteonecrosis. We routinely remove hardware in skeletally immature patients approximately 1 year postoperatively. Complications are rare and include hardware irritation, infection, nonunion, and neurovascular injury.

Important Tips

Preoperative planning is critical for this procedure, and the surgeon should know the intended degree of derotation, the location of the osteotomy relative to the greater trochanter, the length of the nail, and the approximate diameter of the nail prior to entering the operating room.Percutaneous bicortical femoral drill holes are created at the site of the osteotomy prior to reaming to allow for egress of reamings and bone marrow elements at the osteotomy site, which serve as autograft and stimulate bone healing. Additionally, the drill holes provide ventilation to prevent excessive intramedullary pressure during reaming^9-11.External fixator pins are placed proximal and distal to the osteotomy prior to completion of the osteotomy to allow for rotational assessment after completion of the osteotomy. Placing these pins bicortically so that they are secure in the bone and ensuring that the divergence is correct for the intended amount of derotation is critical in this procedure because once the osteotomy is complete, the pins are the only markers of rotation the surgeon has to guide the correction.An external fixator is helpful in holding the femur at the intended degree of derotation during placement of the interlocking screws.

Acronyms & Abbreviations

ROM = range of motionCT = computed tomographyMRI = magnetic resonance imagingAP = anteroposteriorGT = greater trochanterAV = anteversionER = external rotationIR = internal rotationA = anteriorP = posteriorM = medialL = lateralXR = X-rayProx = proximalEx fix = external fixatorWBAT = weight-bearing as toleratedBLE = bilateral lower extremitiesDVT = deep venous thrombosisPT = physical therapyppx = prophylaxisAVN = avascular necrosis (osteonecrosis).

Hip Impingement Location in Maximal Hip Flexion in Patients With Femoroacetabular Impingement With and Without Femoral Retroversion

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.

Evaluation of additional causes of hip pain in patients with femoroacetabular impingement syndrome

Femoroacetabular impingement syndrome (FAIS) is an increasingly prevalent pathology in young and active patients, that has contributing factors from both abnormal hip morphology as well as abnormal hip motion. Disease progression can be detrimental to patient quality of life in the short term, from limitations on sport and activity, as well as the long term through early onset of hip arthritis. However, several concurrent or contributing pathologies may exist that exacerbate hip pain and are not addressed by arthroscopic intervention of cam and pincer morphologies. Lumbopelvic stiffness, for instance, places increased stress on the hip to achieve necessary flexion. Pathology at the pubic symphysis and sacroiliac joint may exist concurrently to FAIS through aberrant muscle forces. Additionally, both femoral and acetabular retro- or anteversion may contribute to impingement not associated with traditional cam/pincer lesions. Finally, microinstability of the hip from either osseous or capsuloligamentous pathology is increasingly being recognized as a source of hip pain. The present review investigates the pathophysiology and evaluation of alternate causes of hip pain in FAIS that must be evaluated to optimize patient outcomes.

Long-Term Outcomes Following Nonoperative Treatment of Prearthritic or Extra-Articular Hip Pain in Women

Introduction

There is an abundance of literature focusing on morphological and surgical outcomes in women with arthritic and prearthritic hip pain. However, no studies have evaluated conservative treatment outcomes, such as physical therapy (PT) and injections, in women with prearthritic or extra-articular hip pain. The purpose of this study is to assess changes in long-term patient-reported outcome measures after nonoperative treatments in women with prearthritic or extra-articular hip pain.

Methods

Twenty-nine female patients (35-65 years old) who presented to a single provider between December 1, 2012 and September 1, 2017 for prearthritic or extra-articular hip pain (Tonnis 1 or less) and had baseline patient-reported outcome data (modified Harris Hip Score [mHHS], Hip Outcome Score [HOS] activities of daily living [ADL] and sport scores, International Hip Outcome Tool-33 [iHOT-33]) available from the institutional hip registry were included. Patients underwent nonoperative treatments for intra-articular or extra-articular hip pain. A follow-up questionnaire was prospectively administered at 3-5 years after the baseline visit.

Results

Most patients underwent targeted PT (n = 27; 93%) to treat intra-articular or extra-articular hip pain. Targeted PT can be defined as primarily exercise-based therapy focusing on hip and lumbar stability. Twelve patients (41%) received injections; of these, 11 were also treated with PT. Overall, significant improvements in mHHS, HOS-ADL, and iHOT-33 scores were observed (p = 0.006, 0.022, and <0.001, respectively). HOS-ADL and iHOT-33 scores improved by a median of 10.3 and 18.0 points, respectively, and were clinically significant. HOS-sport scores also improved but were not statistically significant. There were no differences in patient-reported outcomes between patients who received both PT and injections versus those who received PT, injections, or other treatments.

Conclusions

Nonoperative treatments for prearthritic or extra-articular hip pain in women, specifically PT and/or injections, were associated with sustained improvements in patient-reported outcomes at 3-5 years postbaseline.

Arthroscopic Subspine Decompression Is Commonly Reported in a Heterogenous Patient Population With Concomitant Procedures: A Systematic Review

PURPOSE

To systematically review the evaluation, management, and surgical outcomes of arthroscopic subspine decompression in conjunction with other intra-articular hip preservation procedures.

METHODS

Two databases (PubMed and Embase) were searched from 2010 to 2021, in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, for articles investigating arthroscopic subspine decompression using the key words: "subspine impingement", "AIIS impingement", and "extra-articular impingement." Exclusion criteria included diagnostic studies, failure to report postoperative outcomes, and case series of less than 10 hips. Studies were assessed for patient demographics, diagnostic criteria, clinical findings, concomitant procedures, outcomes, and postoperative complications. The quality of the studies was analyzed by 2 independent reviewers (A.J.C. and A.E.J.) using the Methodological Index for Non-randomized Studies (MINORS).

RESULTS

Ten studies consisting of 438 patients (460 hips, 48.6% female) met the inclusion criteria, with average ages and follow-up ranging from 24.9 to 34.7 years and 6.0 to 44.4 months, respectively. There was 1 Level II study, 3 Level III studies, and 6 Level IV studies. The MINORS criteria yielded an average quality assessment of 13.0 (range: 7-22), with 3 methodological domains demonstrating mean scores of less than 1: unbiased assessment of the study endpoint (.25), loss of follow up less than 5% (.25), and prospective calculation of the study size (.7). The most common exam maneuver used was the subspine impingement test (9 studies). Most subspine decompressions were performed in addition to traditional femoroacetabular impingement syndrome (FAIS) procedures, with only one study (33 hips) reporting solely on isolated subspine osteoplasty. Average preoperative and postoperative modified Harris Hip Score (mHHS) values ranged from 44.93 to 75.7 and 79.5 to 98.0, respectively. Three studies noted improved hip flexion in the postoperative period. Five surgical complications were reported.

CONCLUSIONS

Arthroscopic subspine decompression is commonly reported in a heterogenous patient population with intra-articular hip pathology. A combination of the subspine impingement test and anterior inferior iliac spine (AIIS) morphology on imaging is frequently used for diagnosis. While improved patient-reported outcomes (PROs) are consistently observed following arthroscopic decompression, conclusions are limited by study methodology and concurrent procedures performed at the time of surgery.

LEVEL OF EVIDENCE

IV, systematic review of Level II through Level IV studies.

Treatment of Coxa Profunda With Open Surgical Hip Dislocation, Rim Resection, Cam Resection, and Labral Reconstruction

Coxa profunda presents a unique challenge in surgical treatment approach given global acetabular overcoverage. Arthroscopic treatment can be fraught with difficulty obtaining hip distraction for safe arthroscopic instrumentation, and limited arthroscopic access may prevent sufficient osseous resection of the excess acetabular rim. Although hip arthroscopy use has increased markedly over the past decades for all types of hip pathology, coxa profunda may represent one unique indication for surgical hip dislocation. This technique describes open surgical hip dislocation, rim resection, femoral osteoplasty, and labral reconstruction using anterior tibialis allograft for coxa profunda with combined-type femoroacetabular impingement syndrome and labral ossification.

The Impact of Hip Dysplasia on CAM Impingement

Predisposing factors for CAM-type femoroacetabular impingement (FAI) include acetabular protrusion and retroversion; however, nothing is known regarding development in dysplastic hips. The purpose of this study was to determine the correlation between CAM-type FAI and developmental dysplastic hips diagnosed using X-ray and rotational computed tomography. In this retrospective study, 52 symptomatic hips were included, with a mean age of 28.8 ± 7.6 years. The inclusion criteria consisted of consecutive patients who suffered from symptomatic dysplastic or borderline dysplastic hips and underwent a clinical examination, conventional radiographs and rotational computed tomography. Demographics, standard measurements and the rotational alignments were recorded and analyzed between the CAM and nonCAM groups. Among the 52 patients, 19 presented with CAM impingement, whereas, in 33 patients, no signs of CAM impingement were noticed. For demographics, no significant differences between the two groups were identified. On conventional radiography, the acetabular hip index as well as the CE angle for the development of CAM impingement were significantly different compared to the nonCAM group with a CE angle of 21.0° ± 5.4° vs. 23.7° ± 5.8° (p = 0.050) and an acetabular hip index of 25.6 ± 5.7 vs. 21.9 ± 7.3 (p = 0.031), respectively. Furthermore, a crossing over sign was observed to be more common in the nonCAM group, which is contradictory to the current literature. For rotational alignment, no significant differences were observed. In dysplastic hips, the CAM-type FAI correlated to a lower CE angle and a higher acetabular hip index. In contrast to the current literature, no significant correlations to the torsional alignment or to crossing over signs were observed.

How frequent is absolute femoral retroversion in symptomatic patients with cam- and pincer-type femoroacetabular impingement?

Aims

The frequency of severe femoral retroversion is unclear in patients with femoroacetabular impingement (FAI). This study aimed to investigate mean femoral version (FV), the frequency of absolute femoral retroversion, and the combination of decreased FV and acetabular retroversion (AR) in symptomatic patients with FAI subtypes.

Methods

A retrospective institutional review board-approved observational study was performed with 333 symptomatic patients (384 hips) with hip pain due to FAI evaluated for hip preservation surgery. Overall, 142 patients (165 hips) had cam-type FAI, while 118 patients (137 hips) had mixed-type FAI. The allocation to each subgroup was based on reference values calculated on anteroposterior radiographs. CT/MRI-based measurement of FV (Murphy method) and AV were retrospectively compared among five FAI subgroups. Frequency of decreased FV < 10°, severely decreased FV < 5°, and absolute femoral retroversion (FV < 0°) was analyzed.

Results

A significantly (p < 0.001) lower mean FV was found in patients with cam-type FAI (15° (SD 10°)), and in patients with mixed-type FAI (17° (SD 11°)) compared to severe over-coverage (20° (SD 12°). Frequency of decreased FV < 10° was significantly (p < 0.001) higher in patients with cam-type FAI (28%, 46 hips) and in patients with over-coverage (29%, 11 hips) compared to severe over-coverage (12%, 5 hips). Absolute femoral retroversion (FV < 0°) was found in 13% (5 hips) of patients with over-coverage, 6% (10 hips) of patients with cam-type FAI, and 5% (7 hips) of patients with mixed-type FAI. The frequency of decreased FV< 10° combined with acetabular retroversion (AV < 10°) was 6% (8 hips) in patients with mixed-type FAI and 5% (20 hips) in all FAI patients. Of patients with over-coverage, 11% (4 hips) had decreased FV < 10° combined with acetabular retroversion (AV < 10°).

Conclusion

Patients with cam-type FAI had a considerable proportion (28%) of decreased FV < 10° and 6% had absolute femoral retroversion (FV < 0°), even more for patients with pincer-type FAI due to over-coverage (29% and 13%). This could be important for patients evaluated for open hip preservation surgery or hip arthroscopy, and each patient requires careful personalized evaluation. Cite this article: Bone Jt Open 2022;3(7):557–565.

Rotational abnormalities in dysplastic hips and how to predict acetabular torsion

OBJECTIVES

The aim of this study was to investigate the degree to which conventional radiography can represent the acetabular and femoral rotational alignment profile between dysplastic and borderline-dysplastic hips.

METHODS

A retrospective trial was conducted including 56 borderline-dysplastic and dysplastic hips at a mean age of 28.9 years (range from 18 to 46). Inclusion criteria consisted of symptomatic patients with hip dysplasia undergoing 2-dimensional radiography as well as computed tomography. On radiography, the lateral center edge angle, acetabular hip index, hip lateralization index, acetabular index angle, and the Sharp angle were measured, and the presence of a crossover sign was noted. In computed tomography, the full rotational profile of the lower limb was measured.

RESULTS

Significant correlations were observed in the overall analysis between the anteversion of the acetabulum and the hip lateralization index (mean 0.56, coefficient of regression (CoR) -32.35, p = 0.011) as well as the acetabular index angle with a mean of 11.50 (CoR 0.544, p = 0.018). Similar results were found in the subgroup of dysplastic hips with an acetabular index angle of 13.9 (p = 0.013, CoR 0.74). For the borderline-dysplastic group, no significant correlations between the pelvis radiography and rotational CT were seen.

CONCLUSION

Although the femoral and acetabular torsion cannot be predicted from x-rays, the anteversion of the acetabulum correlates with the acetabular index angle, the hip lateralization index, and eventually the beta angle in dysplastic hips. For borderline-dysplastic hips, such results did not show up, which strongly illustrates the need for computed tomography in these cases.

KEY POINTS

• Much of the current literature focuses on rotational alignment especially with respect to the femur and tibia in healthy patients, although little is known about the acetabular, femoral, and tibial torsion in dysplastic hips. • This is the first study showing significant correlations between the anteversion of the acetabulum and the hip lateralization index as well as the acetabular inclination angle. Also, it is the first study to provide a mechanism for estimation of the torsion of the acetabulum with plain radiography in dysplastic hips. • In borderline-dysplastic hips, no significant correlation was found, which raises the question if a simple x-ray has enough validity to address the acetabular deformity with surgery.

[Treatment strategies for the combination of hip dysplasia, femoroacetabular impingement and malrotation of the proximal femur : How much should be corrected?]

BACKGROUND

Hip dysplasia, FAI and femoral malrotation often occur together, resulting in mixed symptoms and severe biomechanical limitations of the hip.

OBJECTIVES

To report on the current recommendations for the best possible diagnosis and treatment strategies of combination pathologies in hip-preserving surgery.

METHODS

Review and discussion of the relevant literature with consideration of own experience in the treatment of complex combined pathomorphologies of the hip.

RESULTS

Patient history and a thorough clinical examination are key for determining the predominant pathomorphologies causing the symptoms. Standardized conventional ap pelvic and axial images of the hip are the basis for the radiological assessment of the hip, supplemented with MRI, CT and animations of the hip, depending on the case. As the pathologies influence each other functionally, a stepwise approach to treatment is recommended. The functionally most relevant pathology is treated first, followed by further corrections as needed. The primary goal is to achieve a stable hip with normal acetabular coverage, followed by an impingement-free range of motion and normalized musculoskeletal function. Care must be taken in the choice of surgical method to ensure that all pathologies can be adequately treated.

CONCLUSION

Complex, combined pathologies of the hip can be treated sufficiently with hip-preserving surgery. A thorough diagnosis is important in order to recognize the functional interaction of the different pathologies. The goal of the surgical therapy is a correctly covered, stable hip with a normal range of motion.

Assessment of Femoral Torsion on Magnetic Resonance Imaging is More Reliable Using Axial-Oblique Sequences Compared With Standard Axial Slices in Patients With Femoroacetabular Impingement Syndrome

PURPOSE

To determine the agreeability of femoral torsion measurements on axial and oblique axial magnetic resonance imaging (MRI) sequences in patients with femoroacetabular impingement syndrome (FAIS).

METHODS

Patients who underwent primary hip arthroscopy for FAIS between January 2012 to January 2019 were identified. Inclusion criteria were all patients with an MRI scan containing the pelvis and knee imaging. MRI-based measurements of femoral torsion were performed on axial and oblique-axial slices by 2 raters, and inter-rater and intrarater reliability was assessed. Bland Altman plots were constructed to evaluate the agreeability between femoral torsion measurements performed using axial and oblique-axial slices. Bivariate correlation analyses were performed to assess the relationship between measurement methods on each respective scan. A linear regression was performed between measurements performed using axial and oblique-axial sequences.

RESULTS

A total of 164 patients were included. The mean true-axial and oblique axial femoral torsion were 12.2° ± 9.9° and 11.1° ± 9.2°, respectively. The intrarater reliability for axial and oblique-axial measurements were 0.993 and 0.997, respectively. The inter-rater reliability for axial and oblique-axial measurements were 0.925 and 0.965, respectively. The number of differences within the limits of agreement for axial and oblique-axial femoral torsion measurements was 58.54%. On Pearson correlation analysis, strong positive correlations were found between oblique-axial measurements at multiple time points (r = 0.994, P < .001), as well as axial measurements at multiple time points (r = 0.986, P < .001). A strong positive correlation was found between axial and oblique-axial measurements (r = 0.894, P < .001). A significant regression equation indicated that for each additional increase in axial femoral torsion, the oblique-axial femoral torsion increased 0.837 (95% confidence interval 0.772-0.901).

CONCLUSIONS

Femoral torsion values measured on oblique-axial sequences are smaller than on true-axial sequences. Femoral torsion measurements on axial and oblique-axial MRI sequences exhibit poor agreement. Oblique-axial sequences demonstrated greater measurement consistency at multiple timepoints. When evaluating torsional measurements, it is important to delineate which axial sequence was used, especially in patients with suspected severe femoral antetorsion. Standardization of MRI femoral version protocols within one's practice can ensure more consistent decision-making, especially in patients with suspected femoral antetorsion.

LEVEL OF EVIDENCE

Retrospective cohort, level III.

Combined abnormalities of femoral version and acetabular version and McKibbin Index in FAI patients evaluated for hip preservation surgery

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.

Less in-toeing after femoral derotation osteotomy in adult patients with increased femoral version and posterior hip impingement compared to patients with femoral retroversion

In-toeing of the foot was associated with high femoral version (FV), while Out-toeing was associated with femoral-retroversion. Therefore, we report on (i) foot-progression-angle (FPA), (ii) prevalence of In-toeing and Out-toeing, and (iii) clinical outcome of patients treated with femoral-derotation-osteotomy (FDO). We performed a retrospective analysis involving 20 patients (20 hips) treated with unilateral FDO (2017–18). Of them, 14 patients had increased FV, 6 patients had femoral-retroversion. Follow-up time was mean 1 ± 1 years. All patients had minimal 1-year follow-up and the mean age was 29 ± 8 years. Patients with increased FV (FV > 35°) presented with positive posterior-impingement-test and mean FV was 49 ± 11° (Murphy method). Six patients with femoral-retroversion (FV < 10°) had positive anterior impingement test and mean FV of 5 ± 4°. Instrumented gait analysis was performed preoperatively and at follow-up using the Gaitrite system to measure FPA and was compared to a control group of 18 healthy asymptomatic volunteers (36 feet, mean age 29 ± 6 years). (i) Mean FPA increased significantly (P = 0.006) from preoperative 1.3 ± 7° to 4.5 ± 6° at follow-up for patients with increased FV and was not significantly different compared to the control group (4.0 ± 4.5°). (ii) In-toeing decreased from preoperatively (five patients) to follow-up (two patients) for patients with increased FV. Out-toeing decreased from preoperatively (two patients) to follow-up (no patient) for patients with femoral-retroversion. (iii) Subjective-hip-value of all patients increased significantly (P < 0.001) from preoperative 21 to 78 points at follow-up. WOMAC was 12 ± 8 points at follow-up. Patients with increased FV that underwent FDO walked with less In-toeing. FDO has the potential to reduce In-toeing and Out-toeing and to improve subjective satisfaction at follow-up.

Preoperative Alpha Angles Can Predict Severity of Acetabular Rim Chondral Damage in Symptomatic Cam-Type Femoroacetabular Impingement: A Prospective Observatory Study

PURPOSE

To identify the relationship between the alpha angle and the severity of chondrolabral separation as well as acetabular rim chondral damage in symptomatic cam-type femoroacetabular impingement (FAI) with or without focal pincer-type FAI.

METHODS

Patients who received hip arthroscopy under the diagnosis of symptomatic cam-type FAI between January 2018 and August 2018 were identified in a prospectively collected database. Patients were excluded if preoperative lateral center-edge angle <25°, lateral center-edge angle ≥40°, Tönnis grade >1, with previous surgery on the affected hip, or with concomitant synovial disease. The chondrolabral junction was classified into intact chondrolabral junction, stable chondrolabral separation and unstable chondrolabral separation. The classification of acetabular rim chondral damage was modified from the MAHORN (Multicenter Arthroscopy of the Hip Outcomes Research Network) classification: normal/softening, bubble, pocket, flap, and exposed bone. The relationship between the hip morphology and severity of chondrolabral junction and acetabular rim chondral damage was assessed.

RESULTS

A total of 71 patients with the mean age of 33.2 ± 11.0 years were included. Preoperative alpha angles on anteroposterior (AP) or Lauenstein view positively correlated with the severity of acetabular rim chondral damage (P = .028 and P = .016, respectively). A significant increment of the alpha angle between 2 consecutive grades of acetabular rim chondral damage was 7.1° (P = .001) on AP view and 5.2° on Lauenstein view (P = .001). The cut-off values for predicting advanced acetabular rim chondral damage (pocket, flap or bony exposure) were an AP alpha angle of 70° (P = .025) and a Lauenstein alpha angle of 57° (P = .003). There was no significant association between the alpha angle and the severity of chondrolabral separation.

CONCLUSIONS

In patients with symptomatic cam-type FAI with or without focal pincer-type FAI, greater preoperative alpha angles on AP and Lauenstein views can predict more severe acetabular chondral damage.

LEVEL OF EVIDENCE

Level III.

[Imaging in joint-preserving hip surgery]

Instabilität und Impingement stellen die Hauptpathomechanismen dar, die bereits bei jungen Patienten durch erhöhten mechanischen Stress zu chondrolabralen Schäden, schmerzhafter Bewegungseinschränkung und frühzeitiger Coxarthrose führen können. Ziele der gelenkerhaltenden Chirurgie an der Hüfte sind die Korrektur der knöchernen Deformitäten und chondrolabraler Schäden sowie die Wiederherstellung der Gelenkfunktion. Voraussetzung dafür ist die Identifikation der ursächlichen Pathologien an der Hüfte, welche zudem in Kombination auftreten können. Die dezidierte Röntgen- und Magnetresonanzbildgebung der knöchernen Morphologie und der degenerativen Gelenkbinnenläsionen liefern einen essenziellen Beitrag für die Behandlungsindikation und die Behandlungsplanung. Der vorliegende Artikel soll einen kurzen Überblick über die Hüftdeformitäten mit deren Prävalenz, Pathomechanismus und indizierter Therapie sowie detaillierte Empfehlungen über die spezifische radiologische Abklärung geben.

Most of patients with femoral derotation osteotomy for posterior extraarticular hip impingement and high femoral version would do surgery again

AIMS

To assess (1) hip pain and function and ROM; (2) subsequent surgeries, complications; and (3) subjective satisfaction and PROMs in patients undergoing femoral derotation osteotomies.

METHODS

Femoral derotation subtrochanteric osteotomies to treat symptomatic posterior extraarticular ischiofemoral hip impingement were performed in 23 patients (25 hips) between 2013 and 2017. The mean age was 26 ± 8 years (96% female) with a minimum 2-year follow-up (mean follow-up of 4 ± 1 years). Surgical indication was a positive posterior impingement test and limited external rotation (mean 16° ± 8°) in extension in patients with abnormal high femoral version (mean 46° ± 9, measured on CT scans with the Murphy method) and high McKibbin instability index (mean 67°). Femoral osteotomies were combined with a surgical hip dislocation in 96% for cam resection and labrum or cartilage treatment. Preoperative MRI and 3D-CT with dynamic impingement simulation were evaluated.

RESULTS

(1) The posterior impingement test decreased significantly from preoperatively 100% to 4% (p < 0.001). External rotation in extension increased significantly (p < 0.001) from preoperative 16° ± 8 to 44° ± 16°. The MdA score increased significantly from 14 ± 1 to 16 ± 2 (p < 0.001) points.(2) At follow-up, all 25 hips were preserved. No conversion to THA and no revision osteosynthesis was performed. 64% underwent complete hardware removal.(3) 80% of the patients reported at follow-up that they would undergo surgery again. Subjective satisfaction (SHV) increased significantly (p < 0.001) from preoperatively 24% to 84% postoperatively.

CONCLUSIONS

Femoral derotation subtrochanteric osteotomies for the treatment of posterior extraarticular ischiofemoral hip impingement are safe and improve posterior hip pain and function and external rotation in mostly female patients with high femoral version and a high McKibbin instability index.

Cam Morphology Is Associated With Increased Femoral Version: Findings From a Collection of 1,321 Cadaveric Femurs

BACKGROUND

To evaluate the relationship between femoral version (FV) and α angle (AA) in a large osteological collection of human femurs.

METHODS

The University of Iowa-Stanford osteological collection was used to evaluate the research aims. To measure FV and AA, axial photographs of the proximal femurs were taken, referenced from the posterior condylar axis. FV and AA measurements were obtained using ImageJ software, and the relationship between FV and AA was assessed with repeated-measures analysis of variance and generalized linear models. A P value of <.05 was considered statistically significant.

RESULTS

A total of 1321 cadaveric femurs (666 left and 655 right) in 721 cadavers were examined. The average AA for all femurs was 47.8° ± 10.9°, and the average FV for all femurs was 8.53° ± 8.09°. Overall, 191 femurs (14.5%) exhibited cam morphology (AA ≥ 60°). Of the 721 cadavers, 600 had both femurs available for side-to-side comparison. The average FV of femurs with cam morphology was significantly higher than that of femurs without cam morphology (11.70° ± 8.82° vs. 7.99° ± 8.82°, P < .001). Linear regression analysis demonstrated that increased AA was significantly correlated with increased FV (β ± standard error of the mean = 0.21 ± 0.02, P < .0001).

CONCLUSION

In a large osteological collection of human femurs, a significant positive relationship between AA and increasing FV was identified.

CLINICAL RELEVANCE

FAI and hip impingement morphology are more complex than cam or pincer morphology. Cam morphology with high femoral anteversion may allow for normal or near-normal hip mechanics without impingement, and this may partially explain the high rates of asymptomatic cam-type femoroacetabular impingement (FAI) morphology in active and general populations. Given the multiple morphological factors implicated in the development of FAI syndrome, these findings warrant further investigation.

Editorial Commentary: Low-Radiation Dose 3-Dimensional Computed Tomography Scan Reconstruction Is the Best Way to Visualize the Anterior Inferior Iliac Spine-For Now

Femoroacetabular impingement comes in several anatomic variations that may coexist, and subspine impingement is a commonly discussed cause of indirect extra-articular hip pathology. Although a classification system to identify and understand anterior inferior iliac spine morphology has been in place for some time, attempts have been made to visualize and understand the anatomy based on other imaging modalities. Standard radiographs are a common part of the initial patient evaluation pathway, along with thorough history taking and physical examination findings. Magnetic resonance imaging scans are obtained typically to evaluate the soft tissue, muscle, ligaments, articular cartilage, and labrum for pathology. For many hip preservation surgeons, a computed tomography scan with 3-dimensional reconstruction is standard protocol for patients who progress along the treatment pathway toward a surgical procedure because understanding the complex hip anatomy is key to successful surgical treatment. Many hip arthroscopy patients are in their young adult years, and we always attempt to reduce the amount of radiation exposure. Eliminating this computed tomography scan and using standard-of-care magnetic resonance imaging to simplify patient care, reduce radiation, and reduce health care costs would certainly be beneficial to our hip preservation patients.

Editorial Commentary: Both Femoral Acetabular Anteversion and Retroversion May Contribute to the Effect of Femoroacetabular Impingement: What's Your Version?

Femoral anteversion may be a protective factor for hip impingement, whereas hip arthroscopy outcomes are worse for patients with femoral retroversion. Changes in version also affect the location of impingement. The association of increased anteversion with cam lesions may also explain the high number of patients with asymptomatic cam lesions. Thus, some patients may have large α angles but be asymptomatic. Finally, although femoral version is important, it must be considered in the setting of the patient's acetabular morphology. There is a complex interplay of femoral and acetabular morphologies.