3D Characterization of Acetabular Deficiency in Children with Developmental Dysplasia of the Hip

Background The purpose of this study is to determine if a quantitative method can be used to identify differences in 3D morphology between normal and developmentally dysplastic hips and to identify specific areas of undercoverage in children with DDH compared to age- and sex-matched controls. Methods Subjects were included if they were typically developing children with no other underlying conditions affecting their musculoskeletal system and had an available pelvic CT scan (67 hips). Custom software was used to measure standard variables defining acetabular morphology (version, tilt, surface area). Acetabuli were divided into equal octants; coverage angles were measured for each octant of interest. Variables were compared with age- and sex-matched controls (128 hips) using analysis of variance or the Mann–Whitney test. Results Hips with DDH were more anteverted compared to normal hips (DDH: 22.6˚, Control: 16.4˚, p < 0.001). The surface area was similar between groups. 28% of hips had a global deficiency, 24% were anteriorly deficient, 19% were laterally deficient, 10% were anteverted (under covered anteriorly and over covered posteriorly), 3% were posteriorly deficient, and 15% of hips had borderline undercoverage. None of the hips in this cohort were found to be retroverted. Conclusions This is the first study to quantify the 3D acetabular deficiency in children with DDH compared to age- and sex-matched controls. We found wide variability in coverage patterns among dysplastic hips. It is imperative to define the specific acetabular deficiency for each individual patient prior to surgical correction. Level of evidence III – Case–control study.

A Modular Software System for Three Patterns of Acetabular Deficiency Analysis

In order to help orthopedists, evaluate the morphological characteristics of the acetabulum of patients with osteoarthritis, a 3-dimensional (3D) acetabular morphologic parameters measurements software dedicated to the hip was developed. The system includes three modules: 1) Identify the anterior pelvic plane (APP) of the pelvis model; 2) Identify the circular rim of the acetabular wall; 3) Automatically and interactively measure the 3D morphological parameters of the dysplastic acetabulum. The automatic parameter measurement function of this software could fast and accurately measure the 3D morphological parameters of the dysplastic acetabulum. These automatically measured parameters were close to those measured manually with error generally less than 2mm. This software was used to measure acetabular morphological parameters in 61 patients. Two types of dysplastic acetabula were identified by the thickness of the medial wall on the lower margin of the acetabulum Tb: type I was a thin acetabulum (35 cases, Tb≤10.0 mm) and type II was a thick acetabulum (26 cases, Tb &gt;10.0 mm). the result of the acetabular morphological characteristic analysis, it can be found that the thickness of the medial wall is an important morphological characteristic for the THA preoperative surgical planning, and the thickened medial wall could be a misleading factor for the suboptimal placement of the cup.

BORDERLINE DYSPLASIA: ARE THESE HIPS ONLY MILDLY UNCOVERED?

Background: Controversy surrounds classification and treatment of hips with a lateral center-edge angle (LCEA) between 18° and 25°. It remains undetermined as to whether open or arthroscopic procedures are best used to treat patients with borderline dysplasia. We hypothesized that patients with hip pain and borderline acetabular dysplasia have different features of acetabular morphology as determined by other relevant radiographic measures beyond the LCEA. Methods: A retrospective review of patients undergoing hip preservation surgery between January 2010 and December 2015 with either periacetabular osteotomy(PAO) or hip arthroscopy with a LCEA between 18° and 25° was performed. Anteroposterior, Dunn lateral and false profile radiographs were used to measure LCEA, Tönnis Angle, anterior center edge angle (ACEA), anterior (AWI) and posterior (PWI) wall indexes, the femoral epiphyseal acetabular roof (FEAR) index, joint space width, crossover sign, posterior wall sign, P/A index, and femoral alpha angle. An agglomerative hierarchical clustering analysis was then performed on the continuous radiographic variables to identify different subtypes of hip pathomorphology among this patient cohort. There were sex-specific trends in hip morphology. Therefore, we proceeded to perform separate cluster analyses for each sex. Results: Ninety-nine patients underwent surgery in the study period, 77 (78%) were female, and 81 (82%) of these had complete radiographic images for cluster analysis. Mean age was 22.6 years. Hip arthroscopy was performed in 41% of patients and periacetabular osteotomy was performed in 59% of patients. The ACEA (45%), FEAR Index (34%), and AWI (30%) were the most commonly abnormal radiographic parameters among all patients. In female patients, the ACEA (55%), FEAR Index (42%), and AWI (34%) were the most commonly abnormal radiographic parameters. In male patients, an insufficient PWI (48%) was the most common radiographic abnormality. For females, we identified three clusters representing different patterns of hip morphology: impingement morphology; lateral acetabular deficiency, and anterolateral acetabular deficiency (Table 1A). For males, we identified three clusters: postero-lateral acetabular deficiency with global cam morphology, postero-lateral acetabular deficiency with focal cam morphology, and lateral acetabular deficiency without cam morphology (Table 1B). Conclusions: A comprehensive evaluation of radiographic parameters in patients with LCEA 18-25° identifies sex-specific trends in hip morphology and shows a large proportion of dysplastic features among these patients. A thorough evaluation of all pelvic morphology, not just lateral coverage, should be considered when indicating these patients for hip preservation surgeries. Further studies are needed to investigate the outcomes of patients within each of the identified clusters to determine optimal treatment options for each group. [Table: see text][Table: see text]

Mild or Borderline Hip Dysplasia: Are We Characterizing Hips With a Lateral Center-Edge Angle Between 18° and 25° Appropriately?

Background: Controversy surrounds the classification and treatment of hips with a lateral center-edge angle (LCEA) between 18° and 25°. It remains undetermined as to whether periacetabular osteotomy (PAO) or arthroscopic surgery is best used to treat this patient population. Hypothesis: Patients with hip pain and mild or borderline acetabular dysplasia defined by an LCEA between 18° and 25° have different features of acetabular and femoral morphology, as determined by other relevant radiographic measures assessing the anterior and posterior acetabular walls, anterior coverage of the femoral head by the acetabulum, and femoral head and neck junction sphericity. Study Design: Cross-sectional study; Level of evidence, 3. Methods: A retrospective review of patients who had an LCEA between 18° and 25° undergoing hip preservation between January 2010 and December 2015 with either PAO or hip arthroscopic surgery was performed. Anteroposterior, Dunn lateral, and false profile radiographs were used to measure the LCEA, Tönnis angle, anterior center-edge angle (ACEA), anterior wall index (AWI) and posterior wall index (PWI), femoral epiphyseal acetabular roof (FEAR) index and posterior to anterior wall index, and alpha angle and femoral neck-shaft angle. An agglomerative hierarchical clustering analysis was then performed on the continuous radiographic variables to identify different subtypes of hip pathomorphology among the study cohort. There were sex-specific trends in hip morphology. Therefore, we proceeded to perform separate cluster analyses for each sex. Multivariate logistic regression was used to identify radiographic parameters for distinguishing between female patients who underwent hip arthroscopic surgery versus PAO. Results: Ninety-eight patients with hip pain and an LCEA between 18° and 25° underwent surgery in the study period, 77 (78%) were female, and 81 (82%) had complete radiographs for cluster analyses. The mean age was 22.6 years. Hip arthroscopic surgery was performed in 40 (41%) patients, and PAO was performed in 58 (59%) patients. The ACEA (45%), FEAR index (34%), and AWI (30%) were the most commonly abnormal radiographic parameters among all patients. In female patients, the ACEA (55%), FEAR index (42%), and AWI (34%) were the most commonly abnormal radiographic parameters. In male patients, the PWI (48%) was the most common radiographic abnormality. For female patients, 3 clusters representing different patterns of hip morphology were identified: acetabular deficiency with cam morphology, lateral acetabular deficiency, and anterolateral acetabular deficiency. For male patients, 3 clusters were also identified: posterolateral acetabular deficiency with global cam morphology, posterolateral acetabular deficiency with focal cam morphology, and lateral acetabular deficiency without cam morphology. The ACEA (odds ratio [OR], 47.7 [95% CI, 9.6-237.6]; P < .001) and AWI (OR, 3.9 [95% CI, 1.0-15.0]; P = .049) were identified as independent factors predicting which procedure was performed in female patients. Conclusion: A comprehensive evaluation of radiographic parameters in patients with an LCEA between 18° and 25° identified sex-specific trends in hip morphology and showed a large proportion of dysplastic features among these patients. An isolated assessment of the LCEA is an oversimplistic approach that may jeopardize appropriate classification and may provide insufficient data to guide the treatment of hips with additional features of dysplasia and instability.