The lateral center-edge angle as radiographic selection criteria for periacetabular osteotomy for developmental dysplasia of the hip in patients aged above 13 years

Dynamic femoral head coverage following periacetabular osteotomy for developmental dysplasia of the hip

BACKGROUND

Developmental dysplasia of the hip reduces hip stability due to insufficient femoral head coverage. Periacetabular osteotomy surgery aims to increase this coverage. Typically measured using radiographs, most coverage assessments are limited to static hip positions and cannot capture 3D anatomy. This study quantified how dynamic 3D femoral coverage changes during gait and squat after periacetabular osteotomy surgery and compared dynamic coverage to static measures.

METHODS

Pre- and post-surgery CT scans from 38 patients with hip dysplasia were used to reconstruct 3D femur and pelvis bones with which gait and squat were simulated. Models of 38 control subjects were also created. The femoral head was divided into anteromedial, anterolateral, posteromedial, and posterolateral regions. Regional coverage was compared pre- and post-surgery, and against controls, in a static neutral position, during the stance phase of gait, and throughout the squat cycle.

FINDINGS

Lateral coverage increased post-surgery in the static neutral position (anterolateral: 4.9 ± 3.6 % to 13.8 ± 5.6 %; posterolateral: 22.9 ± 15.4 % to 39.8 ± 15.2 % (p ≤ 0.001)) and throughout gait and squat (p ≤ 0.001). Average changes in neutral anterolateral coverage (+8.9 ± 4.5 %) were similar to average changes during gait (+8.1 ± 3.0 %), but not squat (+12.0 ± 1.9 %). Static neutral coverage post-surgery differed significantly from dynamic coverage in every region of the femoral head during all of gait, and most of squat.

INTERPRETATION

While static measures follow some patterns of dynamic coverage after surgery, they miss important variations that can impact joint loading. Understanding how periacetabular osteotomy changes dynamic femoral head coverage can aid with operative planning and assessment to optimize outcomes during daily activities.

Radiographically Apparent Acetabular Sourcil Landmarks Are Created by Comparable Regions of the Pelvis With Extraarticular Bone Variably Confounding Estimates of Joint Coverage

BACKGROUND

The severity of hip dysplasia is characterized by radiographic measurements that require user definition of the acetabular sourcil edge, a bony landmark for which the corresponding three-dimensional (3D) anatomy is not well defined in any imaging plane.

QUESTIONS/PURPOSES

To use digitally reconstructed radiographs to determine: (1) What 3D anatomy is contributing to the "acetabular sourcil" location used to make lateral center-edge angle (LCEA) and anterior center-edge angle (ACEA) measurements in standing AP and false-profile radiographic views, respectively? (2) How do intraobserver and interobserver agreement in LCEA and ACEA translate into agreement of the 3D anatomy being evaluated? (3) How distinct are regions around the acetabular rim circumference that are evaluated by LCEA and ACEA measurements on radiographs?

METHODS

Between January 2018 and May 2019, 72 patients were indicated for periacetabular osteotomy to treat hip dysplasia or acetabular retroversion at our institution. From these patients, a series of 10 patients were identified of the first 12 patients in 2018 who were treated with periacetabular osteotomy, excluding two with missing or low-quality clinical imaging. A second series of 10 patients was identified of the first 11 patients in 2019 who were treated with periacetabular osteotomy and concurrent hip arthroscopy, excluding one who was missing clinical imaging. Pelvis and femoral bone surface models were generated from CT scans of these two series of 10 patients. There were 15 female and five male patients, with a median patient age of 18 years (IQR 17 to 23 years), a preoperative LCEA of 22° (IQR 18° to 24°), and a preoperative ACEA of 23° (IQR 18° to 27°). Exclusion criteria included missing preoperative CT or standard clinical radiographic imaging or severe joint incongruity. To address our first study question, digitally reconstructed radiographs matching each patient's standing AP and false-profile clinical radiographs were created from the segmented CT volumes. A board-certified orthopaedic surgeon and three trained researchers measured LCEA and ACEA on the digitally reconstructed radiographs, and the selected sourcil points were projected back into coordinates in the 3D anatomic space. To address our second study question, intraobserver and interobserver agreement in radiographic coverage angles were related to variations in 3D coordinates of the selected bony anatomy. Lastly, to address our third study question, 3D locations around the acetabular rim identified as contributing to the lateral and anterior sourcil points were summarized across patients in a clockface coordinate system, and statistical analysis of the "time" separating the 3D acetabular contributions of the sourcil edges was performed.

RESULTS

The 3D anatomy contributing to the lateral sourcil was a variable length (27 mm [IQR 15 to 34 mm]) span of the laterosuperior acetabular edges, with contributions by the anterior inferior iliac spine in 35% (7 of 20) of hips. The anterior sourcil reflected a 28-mm (IQR 25 to 31 mm) span of bone from the medial ilium (posterior-medial to the anterior-inferior iliac spine and anterior-lateral to the arcuate line) to the anterior and lateral edges of the acetabulum. Interobserver variability was good for LCEA (intraclass correlation coefficient [ICC] 0.82 to 0.83) and moderate to good for ACEA (ICC 0.73 to 0.79), whereas the agreement in identified 3D sourcil locations varied widely (ICC 0.32 to 0.95). The acetabular edge of the 3D anatomy contributing to the anterior sourcil overlapped the circumferential range of the acetabular rim contributing to the lateral sourcil.

CONCLUSION

Projection of two-dimensional radiographic landmarks contributing to the diagnosis of structural hip deformity into 3D allowed for the identification of the overlapping bony anatomy contributing to radiographically visible anterior and lateral sourcil edges.

CLINICAL RELEVANCE

This work leveraging digitally reconstructed radiographs and 3D pelvis anatomy has found that bone outside the joint contributes to the radiographic appearance of the sourcil and may variably confound estimates of joint coverage. Furthermore, the substantial overlap between the acetabular bone contributing to measurement of the LCEA and ACEA would indicate that these angles measure similar acetabular deformity, and that additional measures are needed to assess anterior coverage independent of lateral coverage.

Erect Weight-Bearing Pelvic Radiographs are Superior to Supine Radiographs for Diagnosis of Mixed Type Acetabular Retroversion Plus Developmental Dysplasia Hip Deformity

PURPOSE

this study focused on the mixed-type deformities of acetabular retroversion (AR) and developmental dysplasia of the hip (DDH) deformity and aimed to ascertain the changes in pelvic tilt from a supine to a standing position in these cases and identify potential underlying mechanisms.

METHODS

A retrospective study was conducted on cases with symptomatic DDH from January 1, 2019, to April 30, 2023. DDH was defined as lateral center-edge angle (LCEA) <20°. AR was diagnosed by using a crossover index threshold of 0.2 in standing pelvic X-ray. Two observers assessed the supine and weight-bearing pelvic radiographs, along with computed tomography (CT) scans. The evaluated parameters included pelvic tilt (sacrofemoral-pubic angle [SFP], symphysis to sacrococcygeal distance [PSSC], pubic symphysis to sacroiliac [PSSI]), AR (crossover index, posterior wall sign), acetabular coverage (LCEA, ischial spine sign [ISS]), and axial rotation of the hemipelvis (pelvic width index, obturator index, and ilio-ischial angle). Acetabular orientation and coverage was measured by CT through anterior sector angle (ASA), posterior sector angle (PSA) and acetabular anteversion (AA). Cases with AR plus DDH were defined as mixed-type deformity. Comparative analyses between mixed-type deformities and DDH cases were performed along with subgroup and correlation analyses within mixed-type cases. Inter-observer and intraobserver reliabilities were assessed using intraclass correlation coefficients.

RESULTS

A total of 85 were included. Out of that 26 cases (30.59%) had mixed-type deformity, where transition from the supine to standing position led to an increased posterior pelvic tilt (SFP [supine: 64.35 ± 4.6°, standing: 74.75 ± 4.16°, P < .001], PSSC [supine: 6.37 ± 2.47, standing: 2.08 ± 1.32, P < .001] and PSSI [supine: 9.47 ± 1.66, standing: 6.33 ± 1.08, P < .001]). Compared to cases with DDH, CT examination revealed a significantly greater anterior acetabular coverage and less posterior superior coverage, with smaller PSA and greater ASA (P < .05) for cases with AR. The superior iliac wing angle (mixed type: 45.63 ± 9.22°, isolated type: 50.70 ± 8.77°, P = .013), inferior iliac wing angle(mixed type: 60.77 ± 8.24°, isolated type: 65.24 ± 8.02°, P = .013), and ischiopubic angle (IPA) (mixed type: 32.27 ± 3.19°, isolated type: 36.71 ± 5.38°, P < .001) were significantly reduced in AR cases, suggesting external rotation of the hemipelvis. Subgroup analysis showed that cases with a higher crossover index had a significantly higher PSSC and a significantly lower IPA.

CONCLUSIONS

AR was observed in 31% of DDH cases and was associated with a notable posterior pelvic tilt during postural transitions. This tilt appeared to be a compensatory mechanism affecting the AR diagnosis. Key changes in the acetabular coverage, including increased anterior coverage and decreased superior posterior coverage, were also observed. Additionally, external rotation of the hemipelvis in mixed-type cases correlated strongly with the extent of AR and anterior acetabular coverage, suggesting that it may be a key contributor to the underlying mechanism of this mixed-type deformity.

How Reliable Is the Measurement of the Lateral Center Edge Angle on Scoliosis Radiographs for Detecting Acetabular Dysplasia?

PURPOSE

Hip dysplasia reportedly occurs in up to 12% of the general population and may be higher in patients with adolescent idiopathic scoliosis (AIS). When using lateral center edge angle (LCEA) measurements to help identify hip dysplasia, it is uncertain if this measurement can be performed reliably on scoliosis radiographs due to parallax. The purpose of this study is to evaluate the reliability of measuring LCEA on scoliosis radiographs compared with standard pelvis radiographs.

METHODS

This study evaluated 40 hips on 20 patients (mean age 12.5 years ± 3.1; 50% Female) who received PA scoliosis radiographs and AP pelvis radiographs within 1 year of each other. Review was performed by 4 pediatric radiologists (2 general, 2 MSK), 2 pediatric orthopaedic surgeons, and 1 research fellow. Radiographic measurement of the LCEA for each hip was first performed on the scoliosis radiograph. After a minimum of 3 days, the LCEA was measured on a pelvis radiograph of the same individual obtained within 1 year of the scoliosis radiograph. Pearson coefficient was used to measure agreement between scoliosis and pelvis radiograph measurements. Intraclass correlation coefficient (ICC) was used to evaluate intraobserver and interobserver agreement. ICC values <0.5 were classified as poor reliability, 0.5 to 0.75 were classified moderate, 0.75 to 0.90 were classified good, and >0.9 indicated excellent reliability.

RESULTS

The mean difference between scoliosis and pelvis radiographs was 54 ± 79 days. There was good-to-excellent interobserver agreement on LCEA measurements made between readers on scoliosis radiographs (ICC: 0.94, 95% CI: 0.90-0.96, P <0.001) and pelvis radiographs (ICC: 0.91, 95% CI: 0.83-0.95, P <0.001), and moderate-to-excellent intraobserver agreement for scoliosis radiographs (ICC range: 0.68 to 0.98; P <0.001) and pelvis radiographs (ICC range: 0.62 to 0.96; P <0.001). There was a strong correlation between LCEA measurements made on scoliosis and pelvis radiographs ( r2 =0.66, P <0.001), and the intermodality agreement between scoliosis and pelvis radiograph LCEA measurements were moderate to good (ICC range: 0.68 to 0.89, P <0.001).

CONCLUSIONS

Overall, there was good-to-excellent agreement between readers on scoliosis and pelvis radiographs, respectively, and moderate-to-excellent intraobserver agreement between LCEA measurements made on scoliosis radiographs and pelvis radiographs, respectively. LCEA measurements made on scoliosis radiographs strongly correlated to the measurements made on pelvis radiographs, and the intermodality ICC was also considered moderate to good. Dedicated pelvis radiographs may not be necessary during scoliosis workup and follow-up surveillance, thereby decreasing radiation exposure, cost, and improving patient care workflow.

LEVEL OF EVIDENCE

Level IV-diagnostic study.

Functional and radiological outcomes of periacetabular osteotomy for hip dysplasia in patients under fifty years using a minimally invasive approach-a single surgeon series with a minimum follow up of two years

PURPOSE

We conducted a retrospective analysis of prospectively collected data to evaluate (1) the extent of surgical correction following minimally invasive periacetabular osteotomy, (2) improvements in functional outcomes and any potential predictors for favourable outcome, and (3) complications after minimally invasive periacetabular osteotomy.

METHODS

A total of 352 minimally invasive periacetabular osteotomy procedures were performed on 312 hip dysplasia patients between 2013 and 2020. Radiological parameters such as lateral centre edge angle, acetabular index, and Tönnis grade of arthritis were calculated. Patients also completed a range of patient reported outcome measures. Wilcoxon signed-rank tests were performed to assess for differences between patient reported outcome measures and radiological outcomes across the follow-up periods. Univariate linear regression and logistic regression were used to assess for predictors of change in functional outcome.

RESULTS

Patients had a significant correction in mean lateral centre edge angle from 17.2° to 35.3° (p < 0.001) and mean acetabular index from 13.2° to - 0.82°. At one year follow-up all patient reported outcome measures were significantly greater than their baseline measurements and this improvement was maintained at two years. Changes in patient reported outcome measures were independent of radiological parameters such as change in the lateral centre edge angle and acetabular index, pre-operative Tönnis grade, and patient factors such as age and sex. A total of 5.11% of patients developed post-operative complications, with four requiring posterior column fixation. Four patients (1.12%) needed a total hip replacement.

CONCLUSION

Minimally invasive periacetabular osteotomy is a safe procedure that provides significant functional outcome improvements following surgery at six months which is maintained at two years. More than three-fourths of patients achieved improvement of iHOT-12 score beyond the minimal clinically important difference and more than half of the patients achieved substantial clinical benefit for iHOT-12 score.

Incorporating patient-specific hip orientation from weightbearing computed tomography affects discrete element analysis-computed regional joint contact mechanics in individuals treated with periacetabular osteotomy for hip dysplasia

Computational models of the hip often omit patient-specific functional orientation when placing imaging-derived bony geometry into anatomic landmark-based coordinate systems for application of joint loading schemes. The purpose of this study was to determine if this omission meaningfully alters computed contact mechanics. Discrete element analysis models were created from non-weightbearing (NWB) clinical CT scans of 10 hip dysplasia patients (11 hips) and oriented in the International Society of Biomechanics (ISB) coordinate system (NWB-ISB). Three additional models were generated for each hip by adding patient-specific stance information obtained via weightbearing CT (WBCT) to each ISB-oriented model: (1) patient-specific sagittal tilt added (WBCT-sagittal), (2) coronal and axial rotation from optical motion capture added to (1; WBCT-combo), and (3) WBCT-derived axial, sagittal, and coronal rotation added to (1; WBCT-original). Identical gait cycle loading was applied to all models for a given hip, and computed contact stress and contact area were compared between model initialization techniques. Addition of sagittal tilt did not significantly change whole-joint peak (p = 0.922) or mean (p = 0.871) contact stress or contact area (p = 0.638). Inclusion of motion-captured coronal and axial rotation (WBCT-combo) decreased peak contact stress (p = 0.014) and slightly increased average contact area (p = 0.071) from WBCT-sagittal models. Including all WBCT-derived rotations (WBCT-original) further reduced computed peak contact stress (p = 0.001) and significantly increased contact area (p = 0.001). Variably significant differences (p = 0.001-1.0) in patient-specific acetabular subregion mechanics indicate the importance of functional orientation incorporation for modeling applications in which local contact mechanics are of interest.

Comparison of Anterior Center-Edge Angle Measured From the Acetabular Sourcil Versus the Anterior Bone-Edge of the Acetabulum: A Descriptive Laboratory Study

Background

Measuring anterior hip coverage on false-profile (FP) radiographs is important for judging anterior hip coverage. Conventionally, the anterior center-edge angle (ACEA) is measured from the anterior edge of the acetabular sourcil (sourcil ACEA); however, the anterior bone edge is also used as the anterior landmark.

Purpose

To determine whether the sourcil ACEA or the bone-edge ACEA better represents the anterior coverage of the hip joint.

Study Design

Descriptive laboratory study.

Methods

We retrospectively observed 49 hips in 49 patients who underwent isolated periacetabular osteotomy. The sourcil ACEA was measured according to the standard procedure. Then, 3-dimensional (3D) volumetric models were made from computed tomographic data. The acetabular surface of the 3D model was labeled and projected onto a simulated FP radiograph, enabling the edge of the acetabulum to be identified. This simulated FP radiograph was used to measure the "true ACEA," as well as the sourcil ACEA and the bone-edge ACEA, and the 3 measurements were compared. Statistical analysis was performed-including testing for normal distribution, measuring interobserver agreement, evaluating differences between measurements, and validating correlation.

Results

The mean sourcil ACEA was 8.6° (range, -3.9° to 31.7°) smaller than that of the true ACEA (P < .001); there was a strong correlation (r = 0.81; P < .001) between the 2. The mean bone-edge ACEA was 16.8° (range, -1.7° to 45.4°) greater than that of the true ACEA (P < .001); there was a moderate correlation (r = 0.57; P < 0.001) between the 2.

Conclusion

Both the sourcil ACEA and bone-edge ACEA differed from the true ACEA. However, compared with the bone-edge ACEA, the sourcil ACEA was numerically closer to the true ACEA and had a stronger correlation with it .

Clinical Relevance

While the exact edge of the true bearing surface of the articular cartilage may not be visible on the FP radiograph, the sourcil ACEA can be effectively utilized as a reliable surrogate when evaluating the anterior acetabular coverage in hip preservation surgery.

Variation in Functional Pelvic Tilt in Female Patients Undergoing Total Hip Arthroplasty With Acetabular Dysplasia

BACKGROUND

As the pelvis is a dynamic structure, the quantification of pelvic tilt (PT) should be done in different hip positions prior to total hip arthroplasty (THA). We sought to investigate functional PT in young female patients undergoing THA and explore the correlation of PT with the extent of acetabular dysplasia. Additionally, we aimed to define the PS-SI (pubic symphysis-sacroiliac joint) index as a PT quantifier on AP pelvis X-ray.

METHODS

Pre-THA female patients under the age of 50 years (n = 678) were investigated. Functional PT in 3 positions (supine, standing, and sitting) were measured. Hip parameters including lateral center-edge angle (LCEA), Tönnis angle, head extrusion index (HEI), and femoro-epiphyseal acetabular roof (FEAR) index were correlated to PT values. The PS-SI/SI-SH (sacroiliac joint-sacral height) ratio was also correlated to PT.

RESULTS

From the 678 patients, 80% were classified as having acetabular dysplasia. Among these patients, 50.6% were bilaterally dysplastic. The mean functional PT of the entire patient group was 7.4°, 4.1°, and -1.3° in the supine, standing and seated positions. The mean functional PT of the dysplastic group was 7.4°, 4.0°, and -1.2° in the supine, standing and seated positions. The PS-SI/SI-SH ratio was found to be correlated to PT.

CONCLUSION

Most of the pre-THA patients had acetabular dysplasia and exhibited anterior PT in the supine and standing positions, most pronounced in the standing position. PT values were comparable between the dysplastic and non-dysplastic group without change with worsening dysplasia. PS-SI/SI-SH ratio can be used to easily characterize PT.

Assessing Acetabular Index Angle in Infants: A Deep Learning-Based Novel Approach

Developmental dysplasia of the hip (DDH) is a disorder characterized by abnormal hip development that frequently manifests in infancy and early childhood. Preventing DDH from occurring relies on a timely and accurate diagnosis, which requires careful assessment by medical specialists during early X-ray scans. However, this process can be challenging for medical personnel to achieve without proper training. To address this challenge, we propose a computational framework to detect DDH in pelvic X-ray imaging of infants that utilizes a pipelined deep learning-based technique consisting of two stages: instance segmentation and keypoint detection models to measure acetabular index angle and assess DDH affliction in the presented case. The main aim of this process is to provide an objective and unified approach to DDH diagnosis. The model achieved an average pixel error of 2.862 ± 2.392 and an error range of 2.402 ± 1.963° for the acetabular angle measurement relative to the ground truth annotation. Ultimately, the deep-learning model will be integrated into the fully developed mobile application to make it easily accessible for medical specialists to test and evaluate. This will reduce the burden on medical specialists while providing an accurate and explainable DDH diagnosis for infants, thereby increasing their chances of successful treatment and recovery.

How Often Do Patients Presenting With Severe Adolescent Idiopathic Scoliosis Have Underlying Hip Dysplasia?

INTRODUCTION

Adolescent idiopathic scoliosis radiographic screening will often include the hips. The purpose of this study is to evaluate the prevalence of hip dysplasia by lateral center edge angle (LCEA) on scoliosis radiographs in patients presenting with severe range (>45 deg) idiopathic curves.

METHODS

We reviewed 200 consecutive patients (400 hips) with idiopathic scoliosis with major coronal curves ≥45 degrees between October 2009 and October 2022. The presenting scoliosis radiograph PA were reviewed for the following variables: major coronal curve direction, coronal balance, and lateral center edge angles. An LCEA value ≤18 was considered dysplastic. To assess potential measurement variability related to parallax of the scoliosis radiographs, the intermodality intraclass correlation coefficient (ICC) was measured from a subset of 20 hip LCEA values from patients with both scoliosis and pelvis radiographs.

RESULTS

A total of 200 patients [mean age: 13.6 (1.8) years; Female: 79%] were reviewed. The mean major curve (SD) was 58.6 degrees (11.4 deg). Overall 19% (37/200) patients or 11% (43/400) of hips had hip dysplasia. Of the dysplastic hips, 16% (6/43, P <0.001) were bilateral and 57% (21/43, P =0.04) were right sided. There was no association between dysplastic hip laterality and ipsilateral or contralateral coronal balance ( P =0.26) or curve direction ( P =0.49). The interobserver ICC for assessment of LCEA on scoliosis radiographs was 0.85, and the intermodality ICC between pelvic and scoliosis radiographs was 0.78.

CONCLUSION

Hip dysplasia was present in 19% of patients presenting with large major curves, and many of these patients had right sided hip dysplasia. There was no association between hip dysplasia laterality and the patient's major curve direction or coronal balance. There was good intermodality reliability (ICC=0.78) between LCEA values in patients who had both scoliosis and pelvis radiographs, and good inter-rater reliability between raters. Radiographic interpretation of adolescent idiopathic scoliosis should focus not only on the description of the curve and ruling out underlying segmentation anomalies but should also include critical assessment of the hips to exclude co-existing hip dysplasia.

LEVEL OF EVIDENCE

Therapeutic study-level IV.

Morphometric assessment of the hip joint in children aged 2-13 years

Our study aimed to evaluate the hip joints of healthy children aged 2-13 years morphometrically through radiographic images. Demographic characteristics of 300 healthy children in our study include an average age of 6.4 years old based on the 2-to-13-year-old bracket and sex classified to 133 girls and 167 boys. A total of 600 normal hips from these children were digitally measured based on Acetabular Index, ACM angle, MZ distance, Sharp angle, CE angle, Femoral Head Coverage Ratio, Cranial, and medial joint space (MJS). *p < 0.05; **p < 0.01 indicated a statistically significant difference. It was found that Acetabular Index, ACM angle, MZ distance, Sharp angle, Cranial, and MJSs decreased with age; Acetabular Depth value and CE angle increased with age; the CE angle differed between the sides (right-left) in the young teens period and in boys; and the cranial joint space (CJS) differed between the sides in girls. In addition, girls had higher values than boys in terms of Acetabular Index, ACM angle, Sharp angle, MZ distance, and Femoral Head Coverage Ratio; CE angle and MJS were higher in girls; and Acetabular Depth Value and CJS did not differ significantly between sexes. Obtaining the normal values will guide in the diagnosis and treatment of many clinical conditions including DDH and Legg-Calve-Perthes disease. It can also be used to compare the hips between healthy children and those diagnosed with Cerebral Palsy.

Determining anterior hip coverage in patients with hip dysplasia using the anterior center-edge angle on Lequesne's false-profile radiograph and on computed tomography

Anterior hip coverage is important for hip stability. As a parameter of anterior hip coverage, the anterior center-edge angle on false-profile radiograph (ACEA FP) is associated with clinical outcomes. With the widespread application of computed tomography (CT), the anterior center-edge angle on CT (ACEA CT) has also been used to measure anterior hip coverage. Little is known about the reproducibility of the ACEA FP and ACEA CT in patients with hip dysplasia or the correlation between the ACEA CT and ACEA FP. In total, 49 hips of 49 patients who underwent periacetabular osteotomy in our center were included. The lateral center-edge angle, Tönnis angle, ACEA FP and ACEA CT were determined. We assessed the intraobserver and interobserver reliability of the ACEA FP and ACEA CT, the effect of the Tönnis angle on the reliability of the ACEA FP and ACEA CT and the correlation between the ACEA CT and ACEA FP. The intraobserver and interobserver interclass correlation coefficients of the ACEA FP were good, and those of the ACEA CT were very good. The Tönnis angle was weakly correlated with inconsistent ACEA FP measurements (P = 0.008) but not with inconsistent ACEA CT measurements (P = 0.600). No correlation between ACEA FP and ACEA CT measurements was observed (P = 0.213-0.665). The reproducibility of the ACEA CT is more consistent than that of the ACEA FP. The oblique acetabular roof had an effect on determining the ACEA FP but not on determining the ACEA CT. No correlation was observed between the measured ACEA FP and ACEA CT values, so the clinical evidence obtained from the ACEA FP cannot be directly applied to the ACEA CT.

Relationship between labral length and symptoms in patients with acetabular dysplasia before rotational acetabular osteotomy

The aim of this study was to investigate the relationship between acetabular labral length and symptoms in patients with acetabular dysplasia. In a retrospective medical record review, 218 patients with acetabular dysplasia who had undergone rotational acetabular osteotomy were identified. After implementing the inclusion and exclusion criteria, 53 patients were analyzed for preoperative symptoms measured by the Japanese Orthopaedic Association Hip Disease Evaluation Questionnaire (JHEQ), acetabular bone morphology parameters by anteroposterior pelvic radiographs and labral parameters by radial magnetic resonance imaging. Spearman's correlation coefficients were calculated among JHEQ scores, bone morphologic parameters and labral parameters. Multiple linear regression models to determine the predictive variables of JHEQ score and labral length were obtained. There was no correlation between bone morphologic parameters and JHEQ scores. Labral length measured anteriorly correlated with JHEQ pain {r [95% confidence interval (CI)] = -0.335 (-0.555, -0.071), P = 0.014}, movement subscale [r (95% CI) = -0.398 (-0.603, -0.143), P = 0.003], mental subscale [r (95% CI) = -0.436 (-0.632, -0.188), P = 0.001] and total JHEQ score [r (95% CI) = -0.451 (-0.642, -0.204), P = 0.001]. The multiple linear regression results showed that anterior labral length was independently associated with JHEQ subscales in some models. Meanwhile, age, acetabular head index and total JHEQ score were independently associated with anterior labral length in all models. Labral length, notably in anterosuperior area, in patients with symptomatic acetabular dysplasia was related to patient's symptom. Labral length may be an important objective image finding that can be used to assess the severity of cumulative hip instability.

Minimally Invasive Radiographic Evaluation of the Dysplastic Hip Joint Configuration in Terms of Surgical Treatment with Hip Preservation by PAO

Introduction

Residual developmental dysplasia of hip (RDDH) is a factor of early osteoarthritis of the hip. The main problems are pain and instability of the hip joint due to inadequate coverage of the femoral head by the acetabulum. The purpose of this study was to radiologically evaluate RDDH after Bernese periacetabular osteotomy (PAO) and to compare RDDH to healthy hips.

Materials and Methods

The radiological parameters of RDDH treated by PAO were retrospectively evaluated. Digital AP pelvic radiographs were taken, including parameters of central edge angle and femoral head coverage, medialization, distalization, and ilio-ischial angle. Clinical assessment is based on the VAS scale. The study group consisted of patients with RDDH, and the control group consisted of patients without RDDH.

Results

After PAO radiological parameters decreased: medialization by 2.68 mm, distalization by 3.65 mm, and ilio-ischial angle by 2.62°. However, there was an increase in the parameters: CEA by 17.61° and FHC by 16.46%. There was a mean 3 point decrease in pain on the VAS scale. There was also a statistically significant radiological difference in the structure of dysplastic hip joints before surgery and healthy hip joints of the control group.

Conclusions

Radiological studies confirmed the effectiveness of the PAO method in the treatment of RDDH. Based on all radiological parameters, differences between healthy and dysplastic hip joints were demonstrated. We believe that a thorough understanding of the values of radiological parameters used to describe dysplastic hip joints will allow us to improve the imaging diagnosis of this condition.

Association of Cam Deformity on Anteroposterior Pelvic Radiographs and More Severe Chondral Damage in Femoroacetabular Impingement Syndrome

BACKGROUND

Abnormal proximal femoral morphology in femoroacetabular impingement syndrome (FAIS) identifiable on the anteroposterior (AP) pelvic radiograph has been described as the "pistol grip" deformity. The effect of a superior cam deformity identified on this radiographic view remains unknown.

PURPOSES

To assess the relationship between AP cam deformity (AP alpha angle [AP AA] >55°) and cartilage injury; to assess the relationship between AP cam deformity and labral injury; and to determine if patient factors are correlated with cartilage and labral injury.

STUDY DESIGN

Case-control study; Level of evidence, 3.

METHODS

Patients undergoing osteochondroplasty and labral repair for FAIS with a single surgeon were identified retrospectively. Intraoperative size, location, and severity of cartilage and labral damage were prospectively collected. Chondrolabral and femoral/acetabular cartilage damage were graded with the Beck labral and cartilage injury criteria. Radiographic data included the AP AA, lateral center-edge angle (LCEA), and maximum femoral alpha angle (MF AA). Patients with hip dysplasia (LCEA <18°; LCEA 18°-25° with acetabular index >10°) were excluded. Outcomes were compared across cartilage and labral severity grades. We report odds ratios (ORs) with 95% confidence intervals and P values from multivariable logistic regressions.

RESULTS

Of the 158 included hips (154 patients), 69% were female and the mean (± standard deviation [SD]) age was 30.3 ± 9.7 years. Increase in age, increase in body mass index (BMI), and male sex were associated with increasing severity of cartilage and labral injury. More severe cartilage damage was associated with increasing AP AA (P < .001) and MF AA (P < .001). The odds of developing a higher category of cartilage injury severity (grade ≥3) were 119% higher (OR, 2.19 [95% CI, 1.36-3.64]; P = .002) for every SD increase (16.7°) in AP AA, adjusting for age, sex, and BMI. The odds of developing a severe labral injury (grade ≥3) were 118% higher (OR, 2.18 [95% CI 1.17-4.32]; P = .018) for every SD increase (10.5°) in MF AA, adjusting for age, sex, BMI, and AP AA.

CONCLUSION

Increasing age and BMI, and male sex are associated with increasing severity of cartilage and labral injury in FAIS. The odds of developing a cartilage injury are significantly higher with independent increases in AP AA and MF AA.

Guided growth versus varus osteotomy for type II avascular necrosis following surgery for developmental dysplasia of the hip

AIMS

The aim of this study was to compare outcomes of guided growth and varus osteotomy in treating Kalamchi type II avascular necrosis (AVN) after open reduction and Pemberton acetabuloplasty for developmental dysplasia of the hip (DDH).

METHODS

This retrospective study reviewed patients undergoing guided growth or varus osteotomy for Kalamchi type II AVN between September 2009 and January 2019. All children who had undergone open reduction and Pemberton acetabuloplasty for DDH with a minimum two-year follow-up were enrolled in the study. Demographic and radiological data, which included the head-shaft angle (HSA), neck-shaft angle (NSA), articulotrochanteric distance (ATD), Sharp angle (SA), and lateral centre-edge angle (LCEA) at baseline, two years, and at the extended follow-up, were compared. Revision rates were evaluated. Clinical outcomes using the Harris Hip Score were assessed two years postoperatively.

RESULTS

A total of 24 patients underwent guided growth and 19 underwent varus osteotomy, over a mean period of 3.3 years (95% confidence interval (CI) 2.8 to 3.8) and 5.2 years (95% CI 4.5 to 6.0), respectively. There were no differences in demographic and preoperative radiological data, except for a younger age at time of acetabuloplasty and larger ATD for the osteotomy group. The HSA did not differ at two years and the extended follow-up because of postoperative rebound in the osteotomy group. The NSA of the osteotomy group remained smaller postoperatively. There were no significant differences in the follow-up ATD, SA, and LCEA, except for a smaller two-year ATD of the osteotomy group. Seven patients (29.2%) in the guided growth group underwent revision surgery and none in the osteotomy group. The Harris Hip Score was similar between groups.

CONCLUSION

Guided growth and varus osteotomy had comparable results in improving caput valgum deformity, given the rebound of lateral tilting of the physis after osteotomy correction. There were no differences in clinical outcomes at two years postoperatively. Cite this article: Bone Joint J 2022;104-B(7):902-908.

Role of the Anterior Center-Edge Angle on Acetabular Stress Distribution in Borderline Development Dysplastic of Hip Determined by Finite Element Analysis

Background: The joint with hip dysplasia is more likely to develop osteoarthritis because of the higher contact pressure, especially in the socket. The lateral center-edge angle (LCEA) is the major indicator for hip dysplasia via radiography. However, the pathological conditions of LCEA angles in the range of 18°–25° are still controversial, which challenges precise diagnosis and treatment decision-making.

Objective: The purpose of this study is to investigate the influence of anterior center-edge angle (ACEA) on the mechanical stress distribution of the hip joint, via finite element analysis, to provide insights into the severity of the borderline development dysplasia.

Methods: From 2017 to 2019, there were 116 patients with borderline developmental dysplasia of the hip (BDDH) enrolled in this research. Based on the inclusion criteria, nine patients were involved and categorized into three LCEA groups with the maximal ACEA differences. Patient-specific hip joint models were reconstructed from computed tomography scans, and the cartilages, including the labrum, were established via a modified numerical method. The finite element analysis was conducted to compare the stress distributions due to the different ACEA.

Results: As ACEA decreased, the maximum stress of the acetabulum increased, and the high stress area developed toward the edge. Quantitative analysis showed that in the cases with lower ACEA, the area ratio of high stress increased, and the contact facies lunata area significantly affected the stress distribution.

Conclusion: For patients with BDDH, both the ACEA and the area of facies lunata played essential roles in determining the severity of hip dysplasia and the mechanical mechanism preceding osteoarthritis.

What happens to the gluteus medius in young and middle-aged patients with hip dysplasia?

BACKGROUND

Much research has focused on quantifying the bony characteristics of patients with developmental dysplasia of the hip (DDH). Far less attention, however, has been paid to muscle abnormalities around the hip such as those in the gluteus medius (GM).

METHODS

We retrospectively examined clinical and imaging data, such as the age of onset and computed tomography (CT) findings, in 108 consecutive hips. Subjects for the control group were selected from our radiology database. Two readers independently evaluated the length (LGM), cross-sectional area (CSA), width (WGM), and thickness (TGM) of the GM and arm of GM (AGM) and angle of the GM activation (AOA) and bony parameters including the acetabulum-head index (AHI), lateral central edge angle (LCEA), acetabular index (AI), femoral offset (FO), and height of the rotation centre of femoral head (HCFH) among all cases using the imaging data.

RESULTS

The patient group included 108 hips. The AGM, LGM, CSA, and TGM were lower in the DDH patients, while AOA was higher. However, there was no significant difference in the WGM between the two groups. Multiple linear regression analysis showed that AGM and AOA were independent factors affecting LCEA. The following regression equation was used: Y(LCEA) = 5.377 * X1 (AGM) - 0.310 * X2 (AOA) - 11.331. The mechanical characteristics of the GM and many bony parameters were significantly correlated (the AGM and AHI, LCEA, AI, FO, but not HCFH; AOA and AHI, LCEA, AI, but not FO or HCFH). The CSA was positively correlated with only HCFH. The rest were not statistical significance linear correlation. The multivariate regression results showed that the age of onset was positively correlated with AGM (r = 0.467). The regression equation used was Y = 9.0 * X (age of onset) - 11.4.

CONCLUSION

We found difference in the morphological and mechanical characteristics of the GM between hips with DDH and hips of normal morphology. Of note, the mechanical characteristics of the GM were influenced by bony parameters in patients with DDH.

Hip dysplasia is not uncommon but frequently overlooked: a cross-sectional study based on radiographic examination of 1,870 adults

Background and purpose - Hip dysplasia in adults is a deformity in which the acetabulum inadequately covers the femoral head. The prevalence is sparingly described in the literature. We investigated the prevalence in Malmö (Sweden) and assessed whether the condition was recognized in the radiology reports.Subjects and methods - All pelvic radiographs performed in Malmö during 2007-2008 on subjects aged 20-70 years with a Swedish personal identity number were assessed. 1,870 digital radiographs were eligible for analysis. The lateral center-edge angle (LCEA) and acetabular index angle (AIA) were measured. Hip dysplasia was defined as an LCEA ≤ 20°. Intraclass correlation coefficients (ICC) for intra-observer measurements ranged from 0.87 (AIA, 95% CI 0.78-0.93) to 0.98 (LCEA, CI 0.97-0.99).Results - The prevalence of hip dysplasia (LCEA ≤ 20°) was 5.2% (CI 4.3-6.3), (98/1,870). There was no statistically significant difference between the sexes for either prevalence of hip dysplasia or mean LCEA. The mean AIA was 0.9° (CI 0.3-1.3) higher in men (4.1 SD 5.5) compared with women (3.2 SD 5.4). The radiologists had reported hip dysplasia in 7 of the 98 cases.Interpretation - The prevalence of hip dysplasia in Malmö (Sweden) is similar to previously reported data from Copenhagen (Denmark) and Bergen (Norway). Our results indicate that hip dysplasia is often overlooked by radiologists, which may influence patient treatment.

The Three-Dimensional Morphology of Femoral Medullary Cavity in the Developmental Dysplasia of the Hip

OBJECTIVE

This study aimed to assess the morphology of the femoral medullary canal in subjects with developmental dysplasia of the hip (DDH) with the intent of improving the design of femoral stems in total hip arthroplasty.

METHODS

Computed tomography images of 56 DDH hips, which were classified into Crowe I to Crowe IV, and 30 normal hips were collected and used to reconstruct three-dimensional morphology of the femoral medullary cavity. Images of twenty-one cross sections were taken from 20 mm above the apex of the lesser trochanter to the isthmus. The morphology of femoral cavity was evaluated on each cross section for the longest canal diameter, the femoral medullary torsion angle (FMTA), and the femoral medullary roundness index (FMRI).

RESULTS

The Crowe IV group displayed the narrowest medullary canal in the region superior to the end of the lesser trochanter, but then gradually aligned with the medullary diameter of the other groups down to the isthmus. The FMTA along the femoral cavity increased with the severity of DDH, but the rate of variation of FMTA along the femoral canal was consistent in the DDH groups. The DDH hips generally showed a larger FMRI than the normal hips, indicating more elliptical shapes.

CONCLUSION

A femoral stem with a cone shape in the proximal femur and a cylindrical shape for the remainder down to the isthmus may benefit the subjects with severe DDH. This design could protect bone, recover excessive femoral anteversion and facilitate the implantation in the narrow medullary canal.