Acetabular Orientation Research Articles

Skeletal hip parameters as determinants of gait in asymptomatic adult subjects

Introduction Acetabular orientation is commonly described by parameters in both the frontal and axial planes. Frequently studied angles such as femoral and acetabular anteversion, neck shaft angle (NSA) and acetabular abduction have been shown to be highly variable, even among asymptomatic subjects. However, it is still not known how these parameters affect functional activities such as gait. The purpose of our study is to investigate the relationship between skeletal and kinematic parameters of the hip during walking. Material and methods One hundred and forty six asymptomatic adult subjects (age = 29.3 ± 11.1 years, 70F) with no prior orthopedic treatment underwent 3D gait analysis and the following kinematic parameters were generated: ROM, Mean, Minimum, Maximum. All subjects underwent full body biplanar X-rays with 3D reconstruction of the pelvis with the following skeletal parameters generated: acetabular abduction, acetabular anteversion (AAnt), NSA and femoral anteversion (FA). Agglomerative Hierarchical Clustering was used for the aforementioned skeletal parameters in order to delimitate 3 classes in each. Kinematics were compared between classes using ANCOVA while controlling for confounding demographic factors (sex, age, height, weight). Results We found no significant differences in gait between the classes of acetabular abduction. As for the femoral anteversion (average FA: class 1: 4.7°, class 2: 16.1° and class 3: 26.9°), 7 kinematic parameters related to the hip in the frontal and axial planes and to the knee in the sagittal plane were found to be significantly different between classes. As for the acetabular anteversion (average AAnt: class 1: 14.1°, class 2: 20.3°, class 3: 25.6°), 7 kinematic parameters related to the hip in both frontal and axial planes and to the knee in the sagittal plane were significantly different. The NSA (average NSA: class 1: 122°, class 2: 129°, class 3: 136°) showed 2 significantly different parameters in sagittal knee kinematics and a significant difference in step length. Discussion This is the first study to assess the role of the skeletal parameters of the hip in dictating gait in asymptomatic subjects. Among frontal parameters, only NSA was related to gait kinematics. As for axial parameters, both acetabular and femoral anteversion (FA). Agglomerative Hierarchical Clustering was used for the aforementioned skeletal parameters in order to delimitate 3 classes in each. Kinematics were compared between classes using ANCOVA while controlling for confounding demographic factors (sex, age, height, weight).

The posterior acetabular wall (PAW): an aid to acetabular orientation at primary THA.

Incorrect acetabular component positioning during total hip arthroplasty (THA) may lead to dislocation, impingement, wear and revision. Surgeons commonly use the transverse acetabular ligament (TAL) as a landmark for acetabular component orientation. The posterior acetabular wall (PAW) is a structure easily viewed on plain radiography and its position can help guide acetabular component position. In this study, we examine the efficacy of preoperative radiographs in predicting cup position relative to the PAW. Prospective data was recorded on radiographic findings of the posterior wall (prominent, normal, deficient) on a consecutive series of 200 primary THAs utilising a standardised posterior approach. The final cup position relative to the wall was recorded (prominent, flush, deep). Cup inclination and version were then assessed by postoperative radiography and any instances of dislocation recorded. There were 117 females and 83 males with a mean age of 66.5 years. 154 were recorded as having a normal PAW on radiographs, 152 had the cup positioned in line with the TAL and flush to the PAW. 29 had a deficient PAW and 27 of these had a cup positioned prominently with 17 having a prominent PAW and of these 16 a deep cup position. Postoperative radiographs showed a mean cup version of 20.8° and inclination of 44.7° using this method. There were 21 outliers (10.5%) with no dislocations at a minimum 12-month follow-up. The TAL is a continuation of the posterior labrum. As such, the posterior wall is a useful adjunct to and surrogate landmark for the TAL. It has the added advantage that it is visible on radiographs and so aids surgical planning with respect to cup positioning.

Three-dimensional orientation of the acetabulum.

This study was designed specifically to determine the normal acetabular orientation and femoral head covering, and whether these are affected by age or sex. Computed tomographic images of normal Japanese hip joints were used (males 60, females 60; mean age 48.3 years, range 15-79 years). Male and female age profiles were matched. The reconstructed 3-D pelvic images were aligned in the anatomical pelvic coordinate system. The acetabular orientation angles and femoral covering angles were measured in the sagittal, coronal, and horizontal planes. In the sagittal plane, the acetabular orientation angle was operative anteversion (O-av), and the femoral covering angles were the anterior and posterior center-edge angles (ACE and PCE). In the coronal plane, they were the Sharp angle (SA) and the lateral center-edge angle (LCE). In the horizontal plane, they were anatomical anteversion (A-av) and the anterior and posterior sector angles (ASA and PSA). The O-av, SA, and A-av were smaller in the male than the female acetabulum (P < 0.01). SA in both males and females was inversely correlated with age (P < 0.01). Both male PCE and PSA were significantly smaller than those of females, while male ASA was larger than female ASA (P < 0.05). The male acetabulum is directed further outward and downward than the female one. However, this does not indicate that the male acetabulum covers the femoral head more, because there is no significant sex difference in the LCE. Femoral coverage is more posteriorly biased in females than in males owing to pelvic inclination. Clin. Anat. 30:753-760, 2017. © 2017Wiley Periodicals, Inc.

Influence of Implant Acetabular Component Orientation on Hip Stability

Introduction.Acetabular component malposition at total hip arthroplasty is a common situation that may affect the frequency of dislocation and the rate of implant friction unit wear. The purpose of the study was to determine the influence of different factors on the variability of acetabular component orientation and evaluate the role of orientation in dislocation development.Patients and methods.Total number of patients made up 1408. Out of them 695 patients were operated on at RSRITO named after R.R. Vreden using standard approaches (group 1), 184 - using low invasive approach (group 2) and 55 patients were admitted with implant head dislocation (group 4). At City St. Petersburg hospitals 474 patients (group 3) were operated on. Orientation of acetabular component (inclination and anteversion angles) was evaluated on digital pelvis and plain hip roentgenograms. Dispersion unifactorial analysis was used to evaluate the dependence of the precision of acetabular component positioning upon the surgeon’s experience, patient’s body mass index, type of surgical approach and the use of guide for acetabular component implantation.Results.Within the first postoperative year the rate of femoral component dislocation in group 1 made up 0.9%. Within the Lewinnek safe zone 76.6% of acetabular components were implanted with the use of a guide and 71.8% without. The rate of dislocation in group 2 made up 71.8% and 63.4% of components were implanted within the safe zone. In group 3 the intra-hospitalization dislocation developed in 1.9% of patients and satisfactory positioning relative to Lewinnek safe zone was achieved in 68.2% of cases. The risk factors for acetabular component malposition included high body mass indices, use of low invasive approach and insufficient experience of the operating surgeon. No direct influence of acetabular component orientation upon the femoral component dislocation was detected.Conclusion. Further studies directed to the more detailed analysis of additional factors that either directly or indirectly affect the implant function and to the optimization of surgical technique that would enable the reproducibility of total hip arthroplasty results are required.

Influence of pelvic tilt on functional acetabular orientation.

Pelvic tilt influences acetabular orientation (AO). Anatomical AO can be measured in relation to the anterior pelvic plane (APP), functional AO can be calculated relative to table's plane. To assess to what extent functional AO is determined by pelvic tilt and if APP and table plane give equal information for correct AO. AO was evaluated by computed tomography (CT) scans of 138 patients. Pelvic tilt, anatomical and functional AO were measured, differences between the two reference planes were calculated. Anatomical and functional acetabular anteversion (AA) were found to be different in 21% of individuals with an enhanced extent of pelvic tilt. Functional AA was increased compared to anatomical AA at high posterior pelvic tilt (p < 0.001). Enlarged anterior tilting of the pelvis reduced APP-related AA (p < 0.002). Anatomical AA positively correlated with pelvic tilt, particularly in females (p < 0.01, correlation coefficient = 0.698, R2 = 0.523). APP and table plane do not provide equal information about AO at enhanced pelvic tilt. Functional orientation of the acetabulum is dependent on pelvic tilt, which itself is influenced by anatomical AA and should therefore be analyzed for precise AO.

Influence of Implant Acetabular Component Orientation on Hip Stability

Introduction. Acetabular component malposition at total hip arthroplasty is a common situation that may affect the frequency of dislocation and the rate of implant friction unit wear. The purpose of the study was to determine the influence of different factors on the variability of acetabular component orientation and evaluate the role of orientation in dislocation development. Patients and methods. Total number of patients made up 1408. Out of them 695 patients were operated on at RSRITO named after R.R. Vreden using standard approaches (group 1), 184 - using low invasive approach (group 2) and 55 patients were admitted with implant head dislocation (group 4). At City St. Petersburg hospitals 474 patients (group 3) were operated on. Orientation of acetabular component (inclination and anteversion angles) was evaluated on digital pelvis and plain hip roentgenograms. Dispersion unifactorial analysis was used to evaluate the dependence of the precision of acetabular component positioning upon the surgeon’s experience, patient’s body mass index, type of surgical approach and the use of guide for acetabular component implantation. Results. Within the first postoperative year the rate of femoral component dislocation in group 1 made up 0.9%. Within the Lewinnek safe zone 76.6% of acetabular components were implanted with the use of a guide and 71.8% without. The rate of dislocation in group 2 made up 71.8% and 63.4% of components were implanted within the safe zone. In group 3 the intra-hospitalization dislocation developed in 1.9% of patients and satisfactory positioning relative to Lewinnek safe zone was achieved in 68.2% of cases. The risk factors for acetabular component malposition included high body mass indices, use of low invasive approach and insufficient experience of the operating surgeon. No direct influence of acetabular component orientation upon the femoral component dislocation was detected. Conclusion. Further studies directed to the more detailed analysis of additional factors that either directly or indirectly affect the implant function and to the optimization of surgical technique that would enable the reproducibility of total hip arthroplasty results are required.

Evaluating Surgeon Estimation of Cup Position in Total Hip Arthroplasty: A Cadaver Study

AbstractInaccurate placement of components during total hip arthroplasty (THA) can lead to significant postoperative complications including revision surgery. Traditionally, surgeons grossly estimate component positioning intraoperatively using anatomical landmarks; however, evidence indicates that this surgeon assessment may not be reliable. The purpose of this study was to determine the accuracy of surgeon estimates of component position as compared with imaging (radiographs and computed tomography [CT] scan) and a new surgical navigation system. Three board-certified orthopaedic surgeons each performed four THA procedures on six cadavers (12 hips). Radiographs and CT scans were obtained postoperatively. The “gold standard” measurements of implanted cup anteversion and inclination were derived from three-dimensional renderings created from postoperative CTs. A reference value for cup position was created by aligning the anterior pelvic plane in each rendering coplanar with the CT table. Following each procedure, surgeons provided their estimate of acetabular cup component orientation. Surgeon estimates were compared with data gathered from postoperative radiographs, CT scans, and the navigation device. Surgeon estimates of anteversion and inclination were within 10 degrees of reference values in 64% (7/11) and 82% (9/11) of cases, respectively. Surgeon estimates of anteversion differed from reference values by a mean of 7.6 ± 5 degrees, whereas inclination differed from reference values by a mean of 6.1 ± 5.1 degrees (all means absolute). Radiographic measurements differed from reference values by 7.8 ± 4.3 degrees (p &gt; 0.05) and 2.7 ± 2.3 degrees (p = 0.06) for anteversion and inclination, respectively, whereas CT values differed by 2.5 ± 1.6 degrees (p = 0.004) and 2.3 ± 2.1 degrees (p = 0.04). The navigation system differed from reference values by 4 ± 4 degrees (p = 0.08) and 4.2 ± 3.2 degrees (p = 0.31). Surgeons underestimated anteversion and inclination by 7.7 ± 4.8 degrees and 6.9 ± 4.8 degrees, respectively. Surgeon underestimation was observed in 8/11 (73%) cases, with anteversion underestimated by &gt; 5 degrees in 5/8 (62%) cases and inclination underestimated by &gt; 5 degrees in 4/8 (50%) cases. Our findings suggest that surgeons tend to underestimate both anteversion and inclination and that the accuracy of their estimates is similar to that of radiographs. CT scans and the navigation system were able to provide more accurate measurements of cup position.

Three-dimensional acetabular orientation measurement in a reliable coordinate system among one hundred Chinese.

Determining three-dimensional (3D) acetabular orientation is important for several orthopaedic scenarios, but the complex geometries of both pelvis and acetabulum make measurements of orientation unreliable. Acetabular orientation may also differ between the sexes or racial groups. We aimed to (1) establish and evaluate a novel method for measuring 3D acetabular orientation, (2) apply this new method to a large population of Chinese subjects, and (3) report relevant characteristics of native acetabular orientation in this population. We obtained computed tomography scans taken for non-orthopaedic indications in 100 Chinese subjects (50 male, 50 female). A novel algorithm tailored to segmentation of the hip joint was used to construct 3D pelvic models from these scans. We developed a surface-based method to establish a reliable 3D pelvic coordinate system and software to semi-automatically measure 3D acetabular orientation. Differences in various acetabular orientations were compared within and between subjects, between male and female subjects, and between our subjects and subjects previously reported by another group. The reported method was reliable (intraclass correlation coefficient >0.999). Acetabular orientations were symmetrical within subjects, but ranged widely between subjects. The sexes differed significantly in acetabular anteversion (average difference, 3.0°; p < 0.001) and inclination (1.5°; p < 0.03). Acetabular anteversion and inclination were substantially smaller among our Chinese subjects than previously reported for American subjects. Thus, our method was reliable and sensitive, and we detected sex differences in 3D acetabular orientation. Awareness of differences between the sexes and races is the first step towards better reconstruction of the hip joint for all individuals and could also be applied to other orthopaedic scenarios.

Analysis of acetabular orientation and femoral anteversion using images of three-dimensional reconstructed bone models.

Radiographic measurements using two-dimensional (2D) plain radiographs or planes from computed tomography (CT) scans have several drawbacks, while measurements using images of three-dimensional (3D) reconstructed bone models can provide more consistent anthropometric information. We compared the consistency of results using measurements based on images of 3D reconstructed bone models (3D measurements) with those using planes from CT scans (measurements using 2D slice images). Ninety-six of 561 patients who had undergone deep vein thrombosis-CT between January 2013 and November 2014 were randomly selected. We evaluated measurements using 2D slice images and 3D measurements. The images used for 3D reconstruction of bone models were obtained and measured using [Formula: see text] and [Formula: see text] (Materialize, Leuven, Belgium). The mean acetabular inclination, acetabular anteversion and femoral anteversion values on 2D slice images were 42.01[Formula: see text], 18.64[Formula: see text] and 14.44[Formula: see text], respectively, while those using images of 3D reconstructed bone models were 52.80[Formula: see text], 14.98[Formula: see text] and 17.26[Formula: see text]. Intra-rater reliabilities for acetabular inclination, acetabular anteversion, and femoral anteversion on 2D slice images were 0.55, 0.81, and 0.85, respectively, while those for 3D measurements were 0.98, 0.99, and 0.98. Inter-rater reliabilities for acetabular inclination, acetabular anteversion and femoral anteversion on 2D slice images were 0.48, 0.86, and 0.84, respectively, while those for 3D measurements were 0.97, 0.99, and 0.97. The differences between the two measurements are explained by the use of different tools. However, more consistent measurements were possible using the images of 3D reconstructed bone models. Therefore, 3D measurement can be a good alternative to measurement using 2D slice images.

Computer assisted navigation in total knee and hip arthroplasty.

Introduction: Computer assisted surgery was pioneered in early 1990s. The first computer assisted surgery (CAS) total knee replacement with an imageless system was carried out in 1997. In the past 25 years, CAS has progressed from experimental in vitro studies to established in vivo surgical procedures. Methods: A comprehensive body of evidence establishing the advantages of computer assisted surgery in knee and hip arthroplasty is available. Established benefits have been demonstrated including its role as an excellent research tool. Its advantages include dynamic pre-operative and per-operative assessment, increased accuracy in correction of deformities, kinematics and mechanical axis, a better alignment of components, better survival rates of prostheses and a better functional outcome. Adoption of computer navigation in the hip arthroplasty is still at an early stage compared to knee arthroplasty, though the results are well documented. Evidence suggests improved accuracy in acetabular orientation, positioning, hip offset and leg length correction. Results: Among the orthopaedic surgeons, navigated knee arthroplasty is gaining popularity though slowly. The uptake rates vary from country to country. The Australian joint registry data shows increased navigated knee arthroplasty from 2.4% in 2003 to 28.6% in 2015 and decreased revision rates with navigated knee arthroplasty in comparison with traditional instrumented knee arthroplasty in patient cohort under the age of 55 years. Conclusion: Any new technology has a learning curve and with practice the navigation assisted knee and hip arthroplasty becomes easy. We have actively followed the evidence of CAS in orthopaedics and have successfully adopted it in our routine practice over the last decades. Despite the cautious inertia of orthopaedic surgeons to embrace CAS more readily; we are certain that computer technology has a pivotal role in lower limb arthroplasty. It will evolve to become a standard practice in the future in various forms like navigation or robotics.

Does Pelvic Incidence Influence the Morphology of the Sacroiliac Joint

Pelvic Incidence is defined as the angle between the perpendicular line to the upper plate of S1 at its midpoint and the line between this point and the center of bicoxofemoral line, it describes the position of femural heads in relation to sacrum. Recently some authors described a direct correlation between high values of PI and large AP pelvic axis (horizontal pelvis) and a wide pelvic ring [1]. Also the acetabular orientation is influenced by PI ; high values of PI means a more vertical acetabulum. Having regard to the relationship between PI and the main structures involved in the load transfer, to date no studies that correlate the morphology of the Sacroiliac Joint (SiJ) and PI were performed. The aim of this study is to evaluate the different morphology of the auricular surface of the sacrum comparing two groups of healthy young people with low ( 40°) PI. We retrospectively analysed 51 consecutive young (between 20 and 35 y.o.) people. After the evaluation of PI the sample was divided into two groups: 31 people belong to the group A (PI 40°). The following morphological parameters of the SiJ were analysed: length of long axis (LLA), length of short axis (LSA), length of oblique axis (LOA), ratio between long and short axis (RLSA), angle between axis (ABA) and surface; global shape of the joint was evaluated; two new parameters were introduced, SiJ Tilt (SiJT), defined as the angle between the vertical line and the long axis of the SiJ and SiJ Slope (SiJS), defined as the angle between the horizontal line and the short axis of the SiJ. We found a strong statistically significant correlations (p-value 0.05) between PI and RLSA, shape, ABA, SiJT and SiJS; a weaker correlations (p-value 0.10) between PI and LLA, LSA were observed; no statistically significant correlation between PI and LOA and surface were observed. The results underline that there is a strong correlation between pelvic morphology and SiJ anatomy. Further studies, about the different pattern of forces distribution among SiJ, will need to be performed to have a better knowledge that could help to understand the biomechanics and pathophysiology of normal and pathological SiJ.

Instability of the hip after anatomical re-alignment in patients with a slipped capital femoral epiphysis.

Several studies have reported the safety and efficacy of subcapital re-alignment for patients with slipped capital femoral epiphysis (SCFE) using surgical dislocation of the hip and an extended retinacular flap. Instability of the hip and dislocation as a consequence of this surgery has only recently gained attention. We discuss this problem with some illustrative cases. We explored the literature on the possible pathophysiological causes and surgical steps associated with the risk of post-operative instability and articular damage. In addition, we describe supplementary steps that could be used to avoid these problems. The causes of instability may be divided into three main groups: the first includes causes directly related to SCFE (acetabular labral damage, severe abrasion of the acetabular cartilage, flattening of the acetabular roof and a bell-shaped deformity of the epiphysis); the second, causes not related to the SCFE (acetabular orientation and poor quality of the soft tissues); the third, causes directly related to the surgery (capsulotomy, division of the ligamentum teres, shortening of the femoral neck, pelvi-trochanteric impingement, previous proximal femoral osteotomy and post-operative positioning of the leg). We present examples drawn from our clinical practice, as well as possible ways of reducing the risks of these complications, and of correcting them if they happen. Cite this article: Bone Joint J 2017;99-B:16-21.

A robust method to extract the anterior pelvic plane from CT volume independent of pelvic pose

Purpose: The anterior pelvic plane (APP) is commonly used as a reference plane to assess acetabular orientation. However, conventional methods for determining the APP may not be accurate and are prone to user variability. To overcome these issues, we developed a robust method to accurately extract the APP independent of pelvic pose using three-dimensional pelvic computed tomography (CT).Materials and methods: Twenty-eight studies for suspected nonmusculoskeletal conditions were obtained. The APP was determined by four landmarks that were automatically extracted from user-defined regions of interest (ROIs) with compensation of pelvic pose. The APP defined from these landmarks was quantitatively compared to the APPs determined by an expert and an unskilled. Intraobserver reliability was measured to evaluate the time-interval variability. Finally, we evaluate the robustness of this method to patient posture using an arbitrarily rotated volume. The intraclass correlation coefficients (ICCs) were calculated to determine the interobserver and intraobserver reliabilities.Results: The ICC values for the four landmarks and the APP were similar between the semiautomated method and expert determination (ICC >0.937). The ICC values for intraobserver reliability over time for our method were all 1, demonstrating high reliability. Furthermore, agreement between the parameters determined from the original volume and the rotated volume was nearly perfect.Conclusions: Our method is a useful measurement tool for the APP as it is robust, and the results were similar to an experienced surgeon’s determination. Furthermore, it was independent to the direction of the CT slice and more robust than a measurement by an unskilled.

Rigid Patient Positioning is Unreliable in Total Hip Arthroplasty

BackgroundTo our knowledge, no study has assessed the ability of rigid patient positioning devices to afford arthroplasty surgeons with ideal acetabular orientation throughout surgery. The purpose of this study is to use robotic arm–assisted computer navigation to assess the reliability of pelvic position in total hip arthroplasty performed on patients positioned with rigid positioning devices. MethodsA prospective cohort of 100 hips (94 patients) underwent robotic-guided total hip arthroplasty in the lateral decubitus position from the posterior approach, 77 stabilized by universal lateral positioner, and 23 by peg board. Before reaming, computed tomography–templated computer software generated true values of pelvic anteversion and inclination based on the position of the robot arm registered to the patient’s preoperative pelvic computed tomography. ResultsMean alteration in anteversion and inclination values was 1.7° (absolute value, 5.3°; range, −20° to 20°) and 1.6° (absolute value, 2.6°; range, −8° to 10°), respectively. And 22% of anteversion values were altered by >10° and 41% by >5°. There was no difference between hip positioners used (P = .36). Anteversion variability was correlated with body mass index (P = .02). ConclusionDespite the use of rigid patient positioning devices—a lateral hip positioner or peg board—this study reveals clinically important malposition of the pelvis in many cases, especially with regard to anteversion. These results show a clear need to pay particular attention to anatomic landmarks or computer-assisted techniques to assure accurate acetabular cup positioning. Patient positioning should not be solely trusted.

Total Hip Arthroplasty in the Spinal Deformity Population: Does Degree of Sagittal Deformity Affect Rates of Safe Zone Placement, Instability, or Revision?

BackgroundChanges in spinal alignment and pelvic tilt alter acetabular orientation in predictable ways, which may have implications on stability of total hip arthroplasty (THA). Patients with sagittal spinal deformity represent a subset of patients who may be at particularly high risk of THA instability because of postural compensation for abnormal spinal alignment. MethodsUsing standing stereoradiography, we evaluated the spinopelvic parameters, acetabular cup anteversion, and inclination of 139 THAs in 107 patients with sagittal spinal deformity. Standing images were compared with supine pelvic radiographs to evaluate dynamic changes in acetabular cup position. Dislocation and revision rates were procured through retrospective chart review. The spinal parameters and acetabular cup positions among dislocators were compared with those who did not dislocate. ResultsThe rate of THA dislocation in this cohort was 8.0%, with a revision rate of 5.8% for instability. Patients who sustained dislocations had significantly higher spinopelvic tilt, T1-pelvic angle, and mismatch of lumbar lordosis and pelvic incidence. Among all patients, 78% had safe anteversion while supine, which decreased significantly to 58% when standing due to increases in spinopelvic tilt. Among dislocating THA, 80% had safe anteversion, 80% had safe inclination, and 60% had both parameters within the safe zone. ConclusionIn this cohort, patients with THA and concomitant spinal deformity have a particularly high rate of THA instability despite having an acetabular cup position traditionally thought of as within acceptable alignment. This dislocation risk may be driven by the degree of spinal deformity and by spinopelvic compensation. Surgeons should anticipate potential instability after hip arthroplasty and adjust their surgical plan accordingly.

Normative 3D acetabular orientation measurements by the low-dose EOS imaging system in 102 asymptomatic subjects in standing position: Analyses by side, gender, pelvic incidence and reproducibility

BackgroundThree-dimensional (3D) acetabular orientation is a fundamental topic in orthopedic surgery. Computed tomography (CT) allows 3D measurement of native acetabular orientation, but with a substantial radiation dose. The EOS imaging system was developed to perform this kind of evaluation, but has not been validated in this indication with specific attention to the acetabulum. We therefore performed a prospective study using EOS to assess: (1) the reproducibility of the 3D acetabulum orientation measures; (2) normative asymptomatic acetabular morphology in standing position, according to side and gender; and (3) the relationship between acetabular anteversion and pelvic incidence. HypothesisThe low-dose EOS imaging system is a reproducible method for measuring 3D acetabular orientation in standing position. Patients and methodsIn a previous prospective study of spine sagittal balance, 165 asymptomatic volunteers were examined on whole-body EOS biplanar X-ray; 102 had appropriate images for pelvic and acetabular analysis, with an equal sex-ratio (53 female, 49 male). These EOS images were reviewed using sterEOS 3D software, allowing automatic measurement of acetabular parameters (anteversion and inclination) and pelvic parameters (pelvic incidence, pelvic tilt and sacral slope) in an anatomical (anterior pelvic plane: APP) and a functional reference plane (patient vertical plane: PVP). ResultsBoth intra- and inter-observer analysis showed good agreement (ICC>0.90); Bland–Altman plot distributions were good. Acetabular anatomical anteversion and inclination relative to APP (AAAPP and AIAPP, respectively) were significantly greater in women than in men, with no effect of side (right AAA: women 21.3°±3.4° vs. men 16.1°±3.3° (P<0001); right AIAPP: women 55.3°±3.7° vs. men 52.5°±3.0° (P<0001); left AAAPP: women 20.9°±3.5° vs. men 15.6°±4.0° (P<0001); left AIAPP: women 54.6°±3.5° vs. men 52.7°±2.8° (P=0003)).The same differences between men and women were observed when measurements were related to PVP. Pelvic incidence subgroup (<44°; 44–62°; >62°) correlated significantly with functional acetabular orientation in standing position: PVP functional anteversion decreased by 5° relative to APP anteversion with incidence <44°, was equal to APP with incidence 44–62°, and or was greater by 4° relative to APP with incidence >62°. DiscussionThe use of a 3D sterEOS software prototype version for 3D reconstruction of the native acetabulum from standard EOS X-ray was shown to be a reliable and reproducible method. This innovative method enabled the reference values of 3D acetabular orientation in standing position to be measured for the first time. The results reinforced the concept of hip-spine relationships, and involved very low radiation dose. Level of evidenceIV prospective study without control group.

Relationship of sagittal alignment and acetabular orientations as measured in upright position in asymptomatic adults

While sagittal alignment is known to significantly influence hip prosthesis positioning after total hip arthroplasty [1] , the effect of sagittal alignment on acetabular orientation has not been previously studied in asymptomatic adult subjects. The aim was to elucidate the relationships between sagittal alignment and acetabular orientation using three-dimensional (3D) reconstruction of the hip in standing position. One hundred and seventy four hips of 87 asymptomatic adult subjects with no prior orthopedic treatment (age = 21.5 ± 2.2 years; 47 males and 40 females) that had undergone full body biplanar X rays, in standing position, with 3D reconstruction of the spine, pelvis and femurs were reviewed. Classic sagittal spino-pelvic alignment parameters were obtained as well as the following hip-specific ones: Lewinek vertical angle, acetabular anteversion (orientation of the acetabulum in the axial plane), abduction (orientation of the acetabulum in the frontal plane) and tilt (orientation of the acetabulum in the sagittal plane), percentage of femoral head coverage by the acetabulum. Pearson correlations were computed between acetabular parameters and sagittal spino-pelvic parameters. Stepwise multiple linear regressions were then used in order to elucidate the most determining sagittal alignment parameters for acetabular orientation. While the percentage of femoral head coverage was independent of all the sagittal alignment parameters, significant correlations (p [2] .

What Are the Results of Surgical Treatment of Hip Dysplasia With Concomitant Cam Deformity?

Periacetabular osteotomy (PAO) is a reliable procedure to correct the deficient acetabular coverage in hips with developmental dysplasia. It is unclear how the presence of additional femoral cam-type deformity might influence the clinical and radiographic treatment results of PAO. (1) Are there differences in clinical scores (WOMAC, EQ-5D) and examination findings (impingement sign) or radiographic measures of acetabular orientation and head sphericity after PAO for isolated acetabular dysplasia when compared with the combined pathology of dysplasia and additional femoral cam deformity? (2) Are these clinical and radiographic findings after combined surgical therapy for additional cam deformity influenced by different pathology-adjusted surgical techniques? From July 2005 to December 2010, 86 patients (106 hips) underwent PAO for hip dysplasia. Surgical and outcome data were prospectively collected and retrospectively reviewed in a comparative observational study. Indications for surgery were a lateral center-edge angle less than 25° and hip pain for at least 6 months. The contraindications for surgery were advanced radiographic osteoarthritis (Kellgren-Lawrence Grade 3), incongruency of joint space, and patient age > 50 years. Depending on preoperative hip ROM, impingement test, and presence of a radiographically visible cam deformity, treatment allocation was performed: Group I: isolated PAO in patients without symptomatic asphericity, Group IIa: PAO with subsequent osteochondroplasty through arthrotomy for patients with symptomatic cam deformity and no labrochondral pathology, and Group IIb: arthroscopically assisted osteochondroplasty and additional labrochondral repair with subsequent PAO when patients had labrochondral lesions in addition to a symptomatic cam deformity. Clinical outcome (impingement test, EQ-5D, WOMAC) as well as radiographic parameters (lateral center-edge angle, crossover sign, alpha angle, osteoarthritis grade) were obtained after a mean followup of 63 ± 18 months (range, 31-102 months) and compared with the baseline data. Eleven patients (13%) were lost to followup. With the numbers available, our study had 80% power to detect a difference between Groups I and II of 10 points on the WOMAC scores. There was no difference in the increase of WOMAC scores in patients with PAO alone (Group I; preoperative score 74 ± 17 versus postoperative 91 ± 15, p = 0.033) when compared with PAO and concurrent osteochondroplasty (Groups II A and B preoperative 73 ± 19 versus postoperative 90 ± 13 p < 0.001). The mean postoperative alpha angles in Group II (38° ± 6°) improved when compared with preoperative values (56° ± 15°; p < 0.001) and were even lower than native offset alpha angles in Group I (47° ± 11°). Clinical scores as well as postoperative radiographic parameters were not different between patients with conventional osteochondroplasty alone (Group IIA) and patients with arthroscopically assisted cam resection and intraarticular labrochondral repair (Group IIB). With the numbers available, we detected no differences in outcome scores and radiographic results between patients who had been treated with PAO alone and patients who underwent combined PAO and offset correction for cam deformity. Although arthroscopically assisted treatment of advanced labrochondral lesions together with osteochondroplasty is possible during PAO and the results were not different in this small study when compared with patients with PAO and osteochondroplasty alone, the type and extent of damage that would indicate additional cartilage surgery over cam resection alone remain unclear. Level III, therapeutic study.

Magnetic resonance imaging evaluation of acetabular orientation in normal Chinese children.

There are no data regarding the acetabular orientation on magnetic resonance imaging (MRI); this study investigates the changes of acetabular orientation with age in normal Chinese children.We retrospectively analyzed the medical records of children who underwent hip MRI examination at our hospital from January 2009 to December 2015. A total of 180 patients with normal MRI reading of the hip joints were included and were divided into 14 groups according to age: from 6 months of age and then for each year from 1 to 16 years. The bony and cartilage acetabular anteversion angle (AAA), acetabular inclination angle (AIA), and acetabular index (AI) were measured. Total bony and cartilage femoral head coverage angles were measured on axial section total femoral head coverage angle (a-TCA) and coronal section total femoral head coverage angle (c-TCA).The mean bony AAA and AIA were 12.2 ± 2.5° and 50.9 ± 2.5°, respectively; both of them stayed constant from the age of 6 months to 16 years. Similar results were found in cartilage AAA (12.1 ± 2.5°) and AIA (41.2 ± 3.0°). There was no difference between bony and cartilage AAA, but bony AIA was significantly larger than cartilage AIA. Bony AI was 24.1 ± 2.4° at the age of 6 months, decreasing to 12.5 ± 2.3° by 12 to 13 years of age; cartilage AI (5.9 ± 1.7°) maintained a steady value with age. The mean bony a-TCA and c-TCA at 6 months were 117.0 ± 5.8° and 127.5 ± 5.1°, increasing to 144.5 ± 4.6° and 140.7 ± 2.5° at the age of 16 years. However, the cartilage a-TCA (145.2 ± 7.2°) and c-TCA (154.1 ± 5.7°) did not change significantly with age.Both bony and cartilage AAA and AIA remain constant up to the age of 16 years in normal Chinese pediatric population. Although the cartilage coverage of femoral head by the acetabulum remains unchanged with age, the bony coverage of femoral head increases.

Acetabular Version Increases After Closure of the Triradiate Cartilage Complex.

Although the etiology of primary femoroacetabular impingement (FAI) is considered developmental, the underlying pathogenic mechanisms remain poorly understood. In particular, research identifying etiologic factors associated with pincer FAI is limited. Knowledge of the physiologic growth patterns of the acetabulum during skeletal maturation might allow conclusions on deviations from normal development that could contribute to pincer-related pathomorphologies. In a population of healthy children, we asked if there were any differences related to skeletal maturation with regard to (1) acetabular version; (2) acetabular depth/width ratio; and (3) femoral head coverage in the same children as assessed by MRIs obtained 1year apart. We prospectively compared 129 MRIs in 65 asymptomatic volunteers without a known hip disorder from a mixed primary/high school population (mean age, 12.7years; range, 7-16years). All participants underwent two MRI examinations separated by a minimum interval of 1year. Based on the status of the triradiate cartilage complex (open versus closed [TCC]), all hips were allocated to the following groups: "open-open"=open TCC at both MRIs (n=45 hips [22 bilateral]); "open-closed"=open TCC at initial and closed TCC at followup MRI (n=26 hips [13 bilateral]); and "closed-closed" group=closed TCC at both MRIs (n=58 hips [29 bilateral]). We assessed acetabular version in the axial plane at five different locations (5, 10, 15, 20mm below the acetabular dome and at the level of the femoral head) as well as three-dimensional (3-D) acetabular depth/width ratio and 3-D femoral head coverage on six radial MRI sequences oriented circumferentially around the femoral neck axis. Using analysis of variance for multigroup comparisons with Bonferroni adjustment for pairwise comparisons, we compared the results between the initial and followup MRI examinations and among the three groups. Acetabular version was increased in hips of the "open-closed" group at the followup MRI compared with the initial MRI at 5mm (-6±4.6 [95% confidence interval {CI}, -7.6 to -3.6] versus -1±5.0 [95% CI, -3.3 to 0.7]; p<0.001), 10mm (0±4.0 [95% CI, -1.6 to 2.1] versus 7±4.6 [95% CI, 4.4-8.7]; p<0.001), and 15mm (8±5.0 [95% CI, 6.1-10.2] versus 15±4.6 [95% CI, 13.3-17.4]; p<0.001) below the acetabular dome. Acetabular version did not change between the initial and followup MRI in the "open-open" and "closed-closed" groups. Independently of the groups, acetabular version was increased in all hips with a fused TCC compared with hips with an open TCC (mean difference measured at 5mm below the acetabular dome at initial MRI examination: 2°±5.9° [95% CI, 0.2°-3.4°] versus -9° ± 4.4° [95% CI, -9.9° to -7.8°]; p<0.001; at followup MRI examination: 1° ± 5.7° [95% CI, 0.1°-2.7°] versus -9° ± 3.8° [95% CI, -10° to -7.6°]; p<0.001). Both acetabular depth/width ratio and femoral head coverage did not differ among the groups or between the initial and followup MRI examinations within each group. Although acetabular depth/width ratio and femoral head coverage remain relatively constant, acetabular version increases with advancing skeletal maturity. There seems to be a relatively narrow timeframe near physeal closure of the TCC within which acetabular orientation changes to more pronounced anteversion. Further studies with greater numbers and longer followup periods are required to support these findings and determine whether such version changes may contribute to pincer-type pathomorphologies. Level II, prospective study.