Three-dimensional orientation of the acetabulum

What Are the Sex-Based Differences of Acetabular Coverage Features in Hip Dysplasia?

BACKGROUND

Eccentric rotational acetabular osteotomy is performed to prevent osteoarthritis caused by developmental dysplasia of the hip (DDH). To achieve sufficient acetabular coverage, understanding the characteristics of acetabular coverage in DDH is necessary. However, the features of acetabular coverage in males with DDH remain unclear. We thought that the differences in acetabular coverage between females and males might be associated with the differences in pelvic morphology between the sexes.

QUESTIONS/PURPOSES

(1) What are the differences in the acetabular coverage between females and males with DDH? (2) What are the differences in the rotations of the ilium and ischium between females and males with DDH? (3) What is the relationship between the rotation of the ilium and ischium and the acetabular coverage at each height in females and males with DDH?

METHODS

Between 2016 and 2023, 114 patients (138 hips) underwent eccentric rotational acetabular osteotomy at our hospital. We excluded patients with Tönnis Grade 2 or higher, a lateral center-edge angle of 25º or more, and deformities of the pelvis or femur, resulting in 100 patients (122 hips) being included. For female patients (98 hips), the median (range) age was 40 years (10 to 58), and for the male patients (24 hips), it was 31 years (14 to 53). We used all patients' preoperative AP radiographs and CT data. The crossover sign, posterior wall sign, and pelvic width index were evaluated in AP radiographs. The rotation of the innominate bone in the axial plane was evaluated at two different heights, specifically at the slice passing through the anterior superior iliac spine and the slice through the pubic symphysis and ischial spine in CT data. Furthermore, we evaluated the anterior and posterior acetabular sector angles. Comparisons of variables related to innominate bone measurements and acetabular coverage measurements between females and males in each patient were performed. The correlations between pelvic morphology measurements and acetabular coverage were evaluated separately for females and males, and the results were subsequently compared to identify any sex-specific differences. For continuous variables, we used the Student t-test; for binary variables, we used the Fisher exact test. A p value less than 0.05 was considered statistically significant.

RESULTS

In the evaluation of AP radiographs, an indicator of acetabular retroversion-the crossover sign-showed no differences between the sexes, whereas the posterior wall sign (females 46% [45 of 98] hips versus males 75% [18 of 24] hips, OR 3.50 [95% confidence interval (CI) 1.20 to 11.71]; p = 0.01) and pelvic width index less than 56% (females 1% [1 of 98] versus males 17% [4 of 24], OR 18.71 [95% CI 1.74 to 958.90]; p = 0.005) occurred more frequently in males than in females. There were no differences in the iliac rotation parameters, but the ischium showed more external rotation in males (females 30° ± 2° versus males 24° ± 1°; p < 0.001). Regarding acetabular coverage, no differences between females and males were observed in the anterior acetabular sector angles. In contrast, males showed smaller values than females for the posterior acetabular sector angles (85° ± 9° versus 91° ± 7°; p = 0.002). In females, a correlation was observed between iliac rotation and acetabular sector angles (anterior acetabular sector angles: r = -0.35 [95% CI -0.05 to 0.16]; p < 0.001, posterior acetabular sector angles: r = 0.42 [95% CI 0.24 to 0.57]; p < 0.001). Similarly, ischial rotation showed a correlation with both acetabular sector angles (anterior acetabular sector angles: r = -0.34 [95% CI -0.51 to -0.15]; p < 0.001 and posterior acetabular sector angles: r = 0.45 [95% CI 0.27 to 0.59]; p < 0.001). Thus, in females, we observed that external iliac rotation and ischial internal rotation correlated with increased anterior acetabular coverage and reduced posterior coverage. In contrast, although acetabular coverage in males showed a correlation with iliac rotation (anterior acetabular sector angles: r = -0.55 [95% CI -0.78 to -0.18]; p = 0.006 and posterior acetabular sector angles: r = 0.74 [95% CI 0.48 to 0.88]; p < 0.001), no correlation was observed with ischial rotation.

CONCLUSION

In males, acetabular retroversion occurs more commonly than in females and is attributed to their reduced posterior acetabular coverage. In females, an increase in the posterior acetabular coverage was correlated with the external rotation angle of the ischium, whereas in males, no correlation was found between ischial rotation and posterior acetabular coverage. In treating males with DDH via eccentric rotational acetabular osteotomy, it is essential to adjust bone fragments to prevent inadequate posterior acetabular coverage. Future studies might need to investigate the differences in acetabular coverage between males and females in various limb positions and consider the direction of bone fragment rotation.

CLINICAL RELEVANCE

Our findings suggest that males with DDH exhibit acetabular retroversion more frequently than females, which is attributed to the reduced posterior acetabular coverage observed in males. The smaller posterior acetabular coverage in males might be related to differences in ischial morphology between sexes. During eccentric rotational acetabular osteotomy for males with DDH, adequately rotating acetabular bone fragments might be beneficial to compensate for deficient posterior acetabular coverage.

Specific pelvic shape in patients with developmental dysplasia of the hip on 3D morphometric homologous model analysis

PURPOSE

To clarify the morphological factors of the pelvis in patients with developmental dysplasia of the hip (DDH), three-dimensional (3D) pelvic morphology was analyzed using a template-fitting technique.

METHODS

Three-dimensional pelvic data of 50 patients with DDH (DDH group) and 3D pelvic data of 50 patients without obvious pelvic deformity (Normal group) were used. All patients were female. A template model was created by averaging the normal pelvises into a symmetrical and isotropic mesh. Next, 100 homologous models were generated by fitting the pelvic data of each group of patients to the template model. Principal component analysis was performed on the coordinates of each vertex (15,235 vertices) of the pelvic homologous model. In addition, a receiver-operating characteristic (ROC) curve was calculated from the sensitivity of DDH positivity for each principal component, and principal components for which the area under the curve was significantly large were extracted (p<0.05). Finally, which components of the pelvic morphology frequently seen in DDH patients are related to these extracted principal components was evaluated.

RESULTS

The first, third, and sixth principal components showed significantly larger areas under the ROC curves. The morphology indicated by the first principal component was associated with a decrease in coxal inclination in both the coronal and horizontal planes. The third principal component was related to the sacral inclination in the sagittal plane. The sixth principal component was associated with narrowing of the superior part of the pelvis.

CONCLUSION

The most important factor in the difference between normal and DDH pelvises was the change in the coxal angle in both the coronal and horizontal planes. That is, in the anterior and superior views, the normal pelvis is a triangle, whereas in DDH, it was more like a quadrilateral.

Fracture-Related Infection in Bicolumnar Acetabular Fracture: A Case Report

Case: A 51-year-old man was affected by a fracture-related infection after a bicolumnar acetabular fracture. A significant alteration of the anatomy was present; thus, a 3D-printed model was useful for planning. A two-stage treatment was planned: in the first stage, implant removal with irrigation and debridement was performed, while in the second stage, a new osteosynthesis and implant of a THA were planned. During the second stage, the patient suffered a cardiogenic shock, so a third surgical procedure was necessary to implant THA. Targeted antibiotic therapy was administered eight weeks after the first stage, with the resolution of the infection. Conclusions: The infection was resolved following the recent guidelines and treating it like a periprosthetic infection with a two-stage revision. A collaboration between specialists in orthopaedics and infectious disease, respectively, and using multidisciplinary approach, were mandatory.

Acetabular Morphology in Patients with Developmental Dysplasia of the Hip with High Dislocation

Purpose

The current study aimed to investigate the morphology of the true acetabulum in developmental dysplasia of the hip (DDH) with high dislocation. A secondary was to evaluate the acetabular cup placement in patients with high dislocation who were treated with total hip arthroplasty (THA).

Materials and Methods

Using a retrospective design, 23 hips with DDH with high dislocation in patients who were treated with THA were included in this study. We measured the depth, width and thickness of the anterior and posterior walls of the original acetabulum using preoperative computed tomography images and investigated the cup size applied in these cases.

Results

The mean depth and width of the acetabulum was 18.4 and 16.2 mm proximal end, 18.4 and 24.3 mm in the middle, and 15.8 and 27.6 mm at the distal part. Mean thickness of the anterior and posterior walls was 10.9 and 23.9 mm at the proximal end, 10.3 and 22.2 mm in the middle, and 10.9 and 22.7 mm at the distal part. A 42-mm cup was using in one hip, a 46-mm cup in three hips, a 48-mm cup in 13 hips, and a 50-mm cup in six hips.

Conclusion

In patients with Crowe IV DDH, the morphology of the acetabulum comprises a triangle that broadens from proximal to distal points, with a relatively thick posterior wall. Reaming the acetabulum posteriorly and inferiorly may enable the placement of a relatively larger cup to achieve stable fixation.

Anteroinferior Hip Instability in Flexion During Dynamic Arthroscopic Examination Is Associated With Abnormal Anterior Acetabular Horn

Background:

The stabilization of the femoral head is provided by the distal acetabulum when the hip is in a flexed position. However, the osseous parameters for the diagnosis of hip instability in flexion are not defined.

Purpose/Hypothesis:

To determine whether the osseous parameters of the distal acetabulum are different in hips demonstrating anteroinferior subluxation in flexion under dynamic arthroscopic examination, compared with individuals without hip symptoms. The hypothesis was that the morphometric parameters of the anterior acetabular horn are distinct in hips with anteroinferior instability compared with asymptomatic hips.

Study Design:

Case-control study; Level of evidence, 3.

Methods:

A total of 30 hips with anteroinferior instability in flexion under dynamic arthroscopic examination were identified. A control group of 60 hips (30 patients), matched by age and sex, was formed from individuals who had undergone pelvis magnetic resonance imaging (MRI) for nonorthopaedic reasons. Unstable and control hips were compared according to the following parameters assessed on axial MRI scans of the pelvis: anterior sector angle (ASA), anterior horn angle (AHA), posterior sector angle (PSA), posterior horn angle (PHA), acetabular version, lateral center-edge angle, acetabular inclination (Tönnis angle), and femoral head diameter.

Results:

The coverage of the femoral head by the anterior acetabular horn was decreased in unstable hips compared with the control group (mean ASA, 54.8° vs 61°, respectively; P < .001). Unstable hips also had a steeper anterior acetabular horn, with an increased mean AHA compared with controls (52.5° vs 46.8°, respectively; P < .001). An ASA <58° had a sensitivity of 0.8, a specificity of 0.68, a negative predictive value of 0.87, and a positive predictive value of 0.56 for anteroinferior hip instability. An AHA >50° had a sensitivity of 0.77, a specificity of 0.72, a negative predictive value of 0.86, and a positive predictive value of 0.57 for anteroinferior hip instability. There was no statistically significant difference in the mean PSA, PHA, acetabular version, lateral center-edge angle, acetabular inclination, or femoral head diameter between unstable hips and controls.

Conclusion:

Abnormal morphology of the anterior acetabular horn is associated with anteroinferior instability in hip flexion. The ASA and AHA can aid in the diagnosis of hip instability.

Radiographic and clinical characteristics associated with a positive PART (Prone Apprehension Relocation Test): a new provocative exam to elicit hip instability

Hip instability due to mild dysplasia can be a diagnostic challenge. The physical exam is an important adjunct to radiographic evaluation for the clinical diagnosis of hip instability. Herein, we describe a new maneuver to replicate hip instability pain, called the PART (Prone Apprehension Relocation Test). We retrospectively identified patients in our institution’s hip preservation registry who presented for evaluation of hip pain. We divided patients into ‘positive’ or ‘negative’ PART and analyzed associated clinical and radiographic findings. Ninety patients (159 hips) were included, 83 female and 7 male, average age 27.3 ± 9.1 years. Thirty-four hips (21.4%) had a positive PART. There were no significant differences in hip range of motion, lateral center edge angle, or in acetabular depth. There was, however, a significant difference in acetabular version at 3 o’clock between the two test groups (18.5 ± 6.9° in negative, 21.2 ± 4.9° in positive, P = 0.045). There was no association between PART and previously described anterior apprehension testing. Historical methods of diagnosing hip dysplasia may not adequately identify patients with clinical hip instability. We describe a new provocative exam, the PART, which may be helpful in replicating hip instability symptoms in patients with anterior acetabular undercoverage. PART positive patients had significantly more acetabular anteversion at the 3 o’clock position, which is measured on computed tomography and is not visible on standard anteroposterior (AP) pelvis or false profile radiographs. We believe that the PART is a valuable supplement to clinical examination and radiographic measurements to identify patients with symptomatic hip instability.

Structural risk factors for low-energy acetabular fractures

In this study, we aimed to clarify proximal femur and acetabular structural risk factors associated with low-energy acetabular fractures in the elderly using three-dimensional (3D) computed tomography (CT). Pelvic bones and femurs were segmented and modeled in 3D from abdominopelvic CT images of 121 acetabular fracture patients (mean age 72 ± 12 years, range 50-98 years, 31 females and 90 males) and 121 age-gender matched controls with no fracture. A set of geometric parameters of the proximal femur and the acetabulum was measured. An independent-samples t-test or a Mann-Whitney U test was used for statistical analyses. The fractured side was used for proximal femur geometry, while the contralateral side was used for acetabular geometry. The neck shaft angle (NSA) was significantly smaller (mean 122.1° [95% CI 121.1°-123.2°] vs. 124.6° [123.6°-125.6°], p = 0.001) and the femoral neck axis length (FNALb) was significantly longer (78.1 mm [77.0-79.2 mm] vs. 76.0 mm [74.8-77.2 mm], p = 0.026) in the fracture group than in the controls when genders were combined. The NSA was significantly smaller both for females (120.2° [117.8°-122.6°] vs. 124.7° [122.5°-127.0°], p = 0.007) and for males (122.7° [121.5°-123.8°] vs. 124.6° [123.4°-125.7°], p = 0.006) in the fracture group. However, only males showed a significantly longer FNALb (80.0 mm [78.9-81.1 mm] vs. 77.8 mm [76.6-79.0 mm], p = 0.025). No statistically significant associations of acetabular geometry with fractures were found. However, the mean values of the acetabular angle of Sharp (34°), the lateral center-edge angle (40°), the anterior center-edge angle (62°), and the posterior center-edge angle (105°) indicated possible over-coverage. In conclusion, our findings suggest that proximal femur geometry is associated with low-energy acetabular fractures. Especially elderly subjects with an NSA smaller than normal have an increased risk of acetabular fractures.

Analysis of acetabular version: Retroversion prevalence, age, side and gender correlations

Introduction

Studies using conventional radiographical signs and computerized tomography (CT) for retroversion of the acetabulum have reported a prevalence of up to 25%. The purpose of this study was to provide a detailed report on acetabular version, gender, age and side differences in a large cohort.

Materials and methods

A total of 404 patients receiving a whole-body CT scan, aged between 16 and 40 years, have been included in the study. The measurement was performed in the transversal plane on three levels: cranial, central and caudal.

Results

The retroverted acetabulum on all three levels had a prevalence of 0.25% (95% confidence interval 0–0.7%). The average central anteversion in men was 16.46° (±4.42) and that in women was 19.31° (±5.04) (p < 0.001). Version increases with age, but a cluster analysis showed this to be a trend (p = 0.068).

Conclusion

Women have a higher average acetabular version than men. Retroversion in a young adult population has a low prevalence when measured with conventional CT. About a tenth of the population has a significantly different contralateral acetabular version.

The translational potential of this article

Global acetabular retroversion has a much lower prevalence than previously reported.

Variations in pelvic dimensions: An anatomical and computed tomography study

The anterior pelvic plane (APP) is a useful anatomical reference with both clinical and research applications in orthopedic surgery and rehabilitation medicine. It is used as a marker for computer-assisted total hip replacement and image-guided assessment of the hip center in clinical gait analysis. Despite its common use, no published data exist on the variations in height and width in an adult population. The aim of this study was to determine the range of dimensions for the anterior pelvic plane found in the Scottish adult population. Thirty-five human cadavers and 100 pelvic computed tomography (CT) scans were examined. Pelvic height and width were measured, and the ratios were determined. The mean width and height for combined cadaver and CT pelves were found to be 238.0 mm (SD 20.1, range 188.3-273.8) and 92.7 mm (SD 10.5, range 71.2-114.7), respectively. The mean width-to-height ratio for all pelves was 2.59 (SD 0.31, range 1.73-3.50). There were no statistically significant differences in means between males and females. The variations of APP dimensions within an adult population are presented. These will be of value in the validation of algorithms for computer navigation and hip joint center calculation in total hip arthroplasty and gait analysis. Furthermore, differences in dimensions between cadaveric and CT measurements have been shown which may have implications for further research and the validity of reference data dependent on data-point acquisition. Clin. Anat. 31:981-987, 2018. © 2018 Wiley Periodicals, Inc.

Three-dimensional femoral head coverage in the standing position represents that measured in vivo during gait

Individuals with over- or under-covered hips may develop hip osteoarthritis. Femoral head coverage is typically evaluated using radiographs, and/or computed tomography (CT) or magnetic resonance images obtained supine. Yet, these static assessments of coverage may not provide accurate information regarding the dynamic, three-dimensional (3-D) relationship between the femoral head and acetabulum. The objectives of this study were to: (1) quantify total and regional 3-D femoral head coverage in a standing position and during gait, and (2) quantify the relationship between 3-D femoral head coverage in standing to that measured during gait. The kinematic position of the hip during standing and gait was measured in vivo for 11 asymptomatic morphologically normal subjects using dual fluoroscopy and model-based tracking of 3-D CT models. Percent coverage in the standing position and during gait was measured overall and on a regional basis (anterior, superior, posterior, inferior). Coverage in standing was correlated with that measured during gait. For total coverage, very little change in coverage occurred during gait (range: 35.0-36.7%; mean: 36.2%). Coverage at each time point of gait strongly correlated with coverage during standing (r = 0.929-0.989). The regions thought to play an important role in weight bearing (i.e. anterior, superior, posterior) were significantly correlated with coverage in standing during the stance phase. Our results suggest that coverage measured in a standing position is a good surrogate for coverage measured during gait. Clin. Anat. 31:1177-1183, 2018. © 2018 Wiley Periodicals, Inc.