Measuring acetabular dysplasia in plain radiographs

Can acetabular dysplasia be measured on axial CT? A measurement for trauma surgeons

BACKGROUND

Acetabular dysplasia has been theorized as a risk factor instability amongst common acetabular fractures, such as posterior wall (PW) fractures. However, common radiographic measurements often cannot be acquired in trauma patients. We evaluated axial computed tomography (CT) scans to identify novel, easily-obtained measurements that correlate with acetabular dysplasia for use in surgical indications and planning.

METHODS

Patients with known acetabular dysplasia undergoing elective periacetabular osteotomy were selected. A different group of patients without pelvic ring or acetabular fractures from an institutional trauma registry were selected as a comparison group. Standard indices of dysplasia were collected, such as center-edge angle (CEA). Acetabular geometric measurements were taken at three axial levels: 0 - cranial CT slice at the dome; 1 - cranial CT where the dome is an incomplete circle; 2 - cranial CT with femoral head visible. Distances between levels were also calculated: Levels 0-1 (Dome Height; DH), Levels 1-2 (Head Height; HH), and Dome-Head Difference (DH - HH = DHD).

RESULTS

DH, HH, and DHD were all significantly correlated with CEA, Tonnis angle, and Sharp's angle in dysplastic hips. All dysplastic hips had DH ≤ 2.5 mm and HH ≥ 1.25 mm. DHD ≤ 0 mm was most specific (93.6 % sensitive, 77.3 % specific) for predicting dysplasia.

CONCLUSION

DH ≤ 2.5 mm, HH ≥ 1.25 mm, and DHD ≤ 0 mm were independently associated with dysplasia on axial CT scans. These measurements may be quickly and easily used by trauma surgeons to assess a trauma-based axial CT scan for acetabular dysplasia.

The Prevalence of Hip Dysplasia on Radiographs for Adolescent Idiopathic Scoliosis

BACKGROUND

During radiographic assessment of adolescent idiopathic scoliosis (AIS), upright images frequently capture the hip. The purpose of this study was to assess the prevalence of radiographic hip dysplasia on postero-anterior (PA) scoliosis radiographs, as defined as a lateral center edge angle (LCEA) ≤25 degrees.

METHODS

All patients with upright PA scoliosis radiographs over a one-year study period at a single tertiary academic medical center (2020 to 2021) were included in the study. Radiographs containing the hip joints were annotated by 3 reviewers for left and right LCEA, and triradiate cartilage (TRC) status. Inter-rater reliability was determined among the 3 reviewers.

RESULTS

Two hundred fifty patients {500 hips, 75.6% female, median age 14 [interquartile range (IQR)=3]} had PA scoliosis radiographs that captured the hip, which qualified for analysis. Seventy-four hips (14.8%) demonstrated evidence of dysplasia (LCEA ≤25 deg) in 55/250 patients (22%). The median LCEA was significantly lower in the dysplastic hip cohort (23.9 deg, IQR=4.8 deg), compared with those without dysplasia (33 deg IQR=7.3 deg; P =0.001). A higher percentage of dysplastic hip patients were female than male (72.7% vs. 27.3%). Patients with bilateral dysplasia had a similar LCEA ( 22.9 deg) [to those with unilateral dysplasia (22.9 deg left, 23.9 deg right, P =0.689)].

CONCLUSIONS

In a cohort of 250 AIS patients, 22% demonstrated evidence of hip dysplasia, as defined as an LCEA ≤2 degrees. The dysplastic patients were more likely to be female. Screening for hip symptomatology in AIS patients may be of benefit, considering the frequency of radiographic hip dysplasia in this population.

LEVEL OF EVIDENCE

III. Type of Evidence: diagnostic.

Student radiographers' knowledge and experience of lateral hip X-ray positioning: A survey

INTRODUCTION

The horizontal beam lateral (HBL) position technique for X-ray imaging has been used for nearly a century; however, this can be challenging for the patient and the practitioner, as it potentially compromises patient dignity. This study explores student radiographers' knowledge and experience of lateral hip positions and their impact on diagnostic quality and patient dignity.

METHOD

A cross-sectional mixed-method online survey of undergraduate diagnostic radiography students was completed. Likert scale assessments, rank ordering questions, and free-test qualitative responses were utilised for questions on knowledge and experience of different positioning, ease to obtain, patient dignity, diagnostic quality, and need for repeats. Data analysis included descriptive statistics and cross-tabulation non-parametric analysis against variables of age, gender and year of study.

RESULTS

Responses were received by n = 42/158 students, a response rate of 27%. The HBL position was the most commonly repeated image (76.6%); the qualitative themes included HBL image quality issues and difficulty in the HBL positioning for elderly or frail patients, often in discomfort and pain. Analysis of student responses to perceived patient dignity in positioning identified 73.8% found the HBL undignified, and 85.7% agreed the Clements-Nakayama (CN) position would be more dignified for patients. The diagnostic image quality of the HBL position (64.2%) was compared to the CN alternative axiolateral (66.6%). Comparison of ease of obtaining the correct position for HBL (47.6%) was higher than CN position (28.6%); this could be due to the lack of experience n = 3/42 (7.1%) of this position.

CONCLUSION

Overall, student radiographers' experience and knowledge of various lateral hip positions observed in clinical practice was good. The CN position scored high for diagnostic image (66.6%) and dignity for the patient (85.7%), over the often repeated HBL position (76.6%), which scored lower for image quality (64.2%) and dignity (76.6%).

IMPLICATIONS FOR PRACTICE

Radiographers should advocate for professional autonomy and explore alternative positioning techniques. Further investigation into the CN position's utilisation, image quality and radiation dose in England is recommended.

Acetabular dysplasia and posterior wall fractures: The missing link?

BACKGROUND

Traumatologists are unable to predict hip instability based on CT scans and standard radiographs in posterior wall (PW) fractures comprising <50-60 % of the wall, necessitating an examination under anesthesia (EUA). Risk factors for instability have not been clarified, but acetabular dysplasia has been theorized as a potential etiology. Unfortunately, dysplasia is difficult to evaluate in the traumatic setting. The purpose of this study was to compare acetabular morphology between unstable and stable fractures with a novel method to detect dysplasia.

METHODS

Patients ≥ 18 years old with a PW fracture that underwent an EUA from 2013 to 2023 were retrospectively identified. For our experimental measurements, the axial distances on CT between the acetabular dome, lateral acetabular opening, and femoral head vertex were recorded. Acetabular geometry was quantified at these levels. Conventional dysplasia metrics (e.g., Tonnis angle) were obtained. Variables were compared between stable and unstable fractures.

RESULTS

58 patients met inclusion criteria with 42 stable versus 16 unstable fractures. Unstable fractures had higher distances between the acetabular dome and femoral head vertex (p > 0.05). They had more cranial fracture exit points (p = 0.0015), lower femoral head coverage (p = 0.0102), and lower posterior acetabular sector angles (p = 0.0281). No other differences in acetabular geometry, demographics, injury characteristics, or other markers of dysplasia were identified.

CONCLUSIONS

Unstable hips demonstrated a more recessed acetabular dome when compared to stable hips. Posterior acetabular femoral head coverage and cranial fracture exit point may be related to hip instability. A larger sample size is needed to validate these findings.

Standard radiographic values for the acetabulum in Japanese adolescents: a cross-sectional study

BACKGROUND

Most previous reports of normal acetabular radiographic values focused on adults or elderly people. Recent reports have described premature hip osteoarthritis in adolescents not caused by acetabular dysplasia. In addition, there is a certain failure rate of surgical treatment for young patients with borderline acetabular dysplasia. Accurate indices for treatment of adolescent hips are unclear because standard measurement values of the adolescent acetabulum have not been reported.

METHODS

This cross-sectional study involved 552 Japanese adolescents aged 12-18 years who had scoliosis or suspected scoliosis and asymptomatic hips. All persons underwent plain standing anteroposterior whole-spine radiography, and measurements were obtained using the pelvic part of the radiograph. We excluded persons who were unable to correctly perform measurements because of conditions such as pelvic rotation or lateral inclination and persons in whom closure of the triradiate cartilage or closure of the secondary ossification centers of the acetabulum had not yet occurred. In 1101 hips, we measured the lateral center-edge angle (LCEA), Tönnis angle, Sharp angle, acetabular head index (AHI), lateral subluxation (LS), vertical subluxation (VS), and peak-to-edge distance (PED). We evaluated the correlation coefficient and coefficient of determination between each parameter and age, height, body weight, and body mass index (BMI) and assessed the intra- and inter-rater reliability of each radiographic parameter.

RESULTS

Among all hips, the mean of each parameter was as follows: LCEA, 27.9° ± 4.8°; Tönnis angle, 5.0° ± 3.7°; Sharp angle, 44.1° ± 3.1°; AHI, 82.1% ± 5.5%; LS, 5.4 ± 1.4 mm; VS, 0.3 ± 1.2 mm; and PED, 14.0 ± 2.3 mm. The correlation between each parameter and age, height, body weight, and BMI was considerably low. Intra- and inter-rater reliability was moderate or good for almost all parameters.

CONCLUSIONS

The values for each radiographic parameter of the acetabulum in this study are considered standard for the adolescent acetabulum without age-related changes. Some parameters differ slightly from the normal values for adults or elderly people in previous reports; thus, we suggest careful evaluation of these parameters for adolescents.

Comparison of Transfer Learning Models in Pelvic Tilt and Rotation Measurement in Pediatric Anteroposterior Pelvic Radiographs

The rotation and tilt of the pelvis during anteroposterior pelvic radiography can lead to misdiagnosis of developmental dysplasia of the hip (DDH) in children. At present, no method exists for accurately and conveniently measuring the precise rotation and tilt angles of pelvic on radiographs. The objective of this study was to develop several rotation and tilt measurement models using transfer learning and digital reconstructed radiographs (DRRs), and to compare their performances on pelvic radiographs. Based on the inclusion criteria, 30 of 92 children who underwent 3D hip CT scans at Xijing Hospital from 2015 to 2020 were included in the study. Using DRR techniques, radiographs were generated by rotating and tilting the pelvis in CT datasets at - 12 to 12° (projected every 3°) and were randomized to a 2:1:1 ratio of training dataset, validation dataset, and test dataset. Five pre-trained networks, including VGG16, Xception, VGG19, ResNet50 and InceptionV3 were used to develop pelvic rotation measurement models and tilt measurement models, and these models were trained with training dataset. The callback function was used during the training to slow down the learning rate when learning was stalled. Then, the validation set was used to optimize each model and compare their performances. At last, we tested the final performances of optimal rotation measurement model and optimal tilt measurement model on test dataset. The mean absolute error (MAE) was employed to assess the performance of the models. A total of 2430 pelvic DRRs were collected based on 30 CT datasets. Among 5 pre-trained transfer learning models, VGG16-Tilt achieved the best tilt prediction performance at the same BS and different LR. VGG16-Tilt model achieved its best performance on validation set at LR = 0.001 and BS = 4, and the final MAE on the test set was 0.5250°. In terms of rotation prediction, VGG16-Rotation also achieved the best performance, and it achieved its best performance on validation set at LR = 0.002 and BS = 8. The final MAE of VGG16-Rotation on the test set was 1.0731°. Pretrained transfer learning models worked well in predicting tilt and rotation angles of the pelvis on radiographs in children. Among them, VGG16-Tilt and VGG16-Rotation had the best effect in dealing with such problems despite their simple structures. These models deployed in devices can give orthopedic surgeons a powerful aid in DDH diagnosis.

Effects of pelvic obliquity and limb position on radiographic leg length discrepancy measurement: a Sawbones model

Purpose

Potential sources of inaccuracy in leg length discrepancy (LLD) measurements commonly arise due to postural malalignment during radiograph acquisition. Preoperative planning techniques for total hip arthroplasty (THA) are particularly susceptible to this inaccuracy, as they often rely solely on radiographic assessments. Owing to the extensive variety of pathologies that are associated with LLD, an understanding of the influence of malpositioning on LLD measurement is crucial. In the present study, we sought to characterize the effects of varying degrees of lateral pelvic obliquity (PO) and mediolateral limb movement in the coronal plane on LLD measurement error (ME).

Methods

A 3-D sawbones model of the pelvis with bilateral femurs of equal-length was assembled. Anteroposterior pelvic radiographs were captured at various levels of PO: 0°, 5°, 10°, and 15°. At each level of PO, femurs were individually rotated medio-laterally to produce 0°, 5°, 10°, and 15° of abduction/adduction. LLD was measured radiographically at each position combination. For all cases of PO, the right-side of the pelvis was designated as the higher-side, and the left as the lower-side.

Results

At 0° PO, 71% of tested variations in femoral abduction/adduction resulted in LLD ME < 0.5-cm, while 29% were ≥ 0.5-cm, but < 1-cm. ME increased progressively as one limb was further abducted while the contralateral limb was simultaneously further adducted. The highest ME occurred with one femur abducted 15° and the other adducted 15°. Similar magnitudes of ME were seen in 98% of tested femoral positions at 5° of PO. The greatest ME (~ 1 cm) occurred at the extremes of right-femur abduction and left-femur adduction. At 10° of PO, a higher prevalence of cases exhibited LLD ME > 0.5-cm (39%) and ≥ 1-cm (8%). The greatest errors occurred at femoral positions similar to those seen at 5° of PO. At 15° of PO, half of tested variations in femoral position resulted in LLD ME > 1-cm, while 22% of cases produced errors > 1.5-cm. These clinically significant errors occurred at all tested variations of right-femur abduction, with the left-femur in either neutral position, abduction, or adduction.

Conclusion

This study aids surgeons in understanding the magnitude of radiographic LLD ME produced by varying degrees of PO and femoral abduction/adduction. At a PO of ≤5°, variations in femoral abduction/adduction of up to 15° produce errors of marginal clinical significance. At PO of 10° or 15°, even small changes in mediolateral limb position led to clinically significant ME (> 1-cm). This study also highlights the importance of proper patient positioning during radiograph acquisition, demonstrating the need for surgeons to assess the quality of their radiographs before performing preoperative templating for THA, and accounting for PO (> 5°) when considering the validity of LLD measurements.

Reliability of Goldberg Scoring System in the Radiographic Evaluation of Bony Union after Bone Grafting

Background

Evaluation of bony union after bone grafting is very important in orthopedic surgery. The aim of this study was to verify inter- and intraobserver reliability of the Goldberg scoring system for radiographic evaluation of bony union after bone grafting in various situations of animal models.

Methods

Twenty-seven male C57/BL6 mice, which lack the ability to synthesize galactose-alpha-1,3-galactose (GalT KO mice), and 9 C57/BL6 mice carrying a wild-type gene were used as animal models. We divided the mice into four groups. In group 1, syngenic bone grafting and intramedullary fixation were performed (9 wild type C57BL/6 mice). In group 2, allogenic bone grafting was performed (9 GalT KO mice). In group 3, an alpha-galactosidase-treated porcine xenograft was transplanted into the femur to reduce the antigenicity (9 GalT KO mice). In group 4, a non-treated porcine xenobone grafting was performed (9 GalT KO mice). The level of radiographic bony union (Goldberg method) was assessed by three orthopedic surgeons. Intra- and interobserver reliability for radiographic evaluation was assessed.

Results

In the Goldberg scoring system, most of the radiographic measurements showed substantial to almost perfect intraobserver reliability. The total score showed substantial intraobserver reliability. The kappa coefficient (κ) of the first examiner was 0.603, the κ of the second examiner was 0.790, and the κ of the third examiner was 0.758. The scoring system showed substantial interobserver reliability. The κ of the first session was 0.641 and the κ of the second session was 0.649.

Conclusions

The Goldberg scoring system is a reliable tool for radiographic evaluation of bony union after bone grafting.

Stability in Pelvic Triple Osteotomies in Children Using Resorbable PLGA Screws for Fixation

BACKGROUND

The triple pelvic osteotomy (TPO) is a major redirectional osteotomy used to improve the acetabular coverage of the femoral head in selected pediatric patients with hip disorders. Traditionally the iliac osteotomy is stabilized by metal screws that require a second surgery for removal. Despite favorable results for both adults and children in related pelvic osteotomies, resorbable implants have not previously been used for TPOs.This study aims to suggest a novel modified TPO surgical method in children using resorbable poly lactic-co-glycolic acid (PLGA) screws for fixation and to radiographically evaluate the postoperative stability achieved by these implants in a case series.

METHODS

All patients (n=11) with dysplasia of the hip (2), Perthe disease (5), or Down syndrome (4), who underwent primary TPO surgery during 2013 to 2019, using resorbable PLGA screws for fixation were included. The stability of the osteotomy was evaluated in the postoperative radiograph series using the acetabular index, migration percentage, Sharp's angle and the center-edge angle. The osteotomy angle was introduced as a parameter to confirm the postoperative integrity of the achieved correction. All cases were evaluated until radiographic healing of the iliac osteotomy. Hospital notes were analyzed for complications or local reactions in relation to the implants.

RESULTS

In all studied hips, the overall achieved correction was well maintained. The mean (SD) correction achieved, from the preoperative images to the last measurable postoperative image, was a 16.7 degrees decrease for Sharp angle, a 20.9 degrees decrease in acetabular index and a 24.7 degrees increase for the center-edge angle, respectively. There were no complications related to the bioabsorption of the implants.

CONCLUSION

The present findings suggest that the modified TPO method, using resorbable PLGA screws, provides sufficient stability and appears to be a promising alternative to traditional TPO. Avoiding implant removal is a major benefit in a pediatric population. Resorbable screws enable the surgeon to place implants with more degrees of freedom since later implant removal is not a limiting factor.

LEVEL OF EVIDENCE

Level IV-case series.

3D MRI of the Hip Joint: Technical Considerations, Advantages, Applications, and Current Perspectives

Magnetic resonance imaging (MRI) is a common choice among various imaging modalities for the evaluation of hip conditions. Conventional MRI with two-dimensional acquisitions requires a significant amount of time and is limited by partial-volume artifacts and suboptimal fluid-to-cartilage contrast. Recent hardware and software advances have resulted in development of novel isotropic three-dimensional (3D) single-acquisition protocols that cover the volume of the entire hip and can be reconstructed in arbitrary planes for submillimeter assessment of bony and labro-cartilaginous structures in their planes of orientation. This technique facilitates superior identification of small labral tears and other hip lesions with better correlations with arthroscopy. In this review, we discuss technical details related to 3D MRI of the hip, its advantages, and its role in commonly encountered painful conditions that can be evaluated with great precision using this technology. The entities described are femoroacetabular impingement with acetabular labral tears, acetabular dysplasia, avascular necrosis, regional tendinopathies and tendon tears, bursitis, and other conditions.

Assessing the Weight-Bearing Surface in Dysplastic Acetabulae: The Sourcil Index

Background

Although a variety of standardized measurements have been described to evaluate acetabular dysplasia, no single measurement is without limitations. We describe the Sourcil Index (SI), a novel measure of the weight-bearing surface of the acetabulum on anteroposterior pelvis films. The SI is the angle formed by the medial and lateral margins of the sourcil and the center of rotation of the femoral head.

Methods

Anteroposterior pelvis radiographs of skeletally mature patients from 2015 were reviewed. Studies with fractures or implants were excluded. Films were read by 2 orthopedic surgeons and a radiologist 3 times each, 8 weeks apart. The SI, Sharp's Angle (SA), and lateral center edge angle (LCEA) were recorded. Pearson intraclass correlation coefficients with 95% confidence intervals were calculated. The SI was then compared to the SA and LCEA to preliminarily assess diagnostic accuracy.

Results

Five hundred thirty-five hips in 292 patients met inclusion. Intraobserver reliability is as follows: SI = 0.95 (0.93-0.98), LCEA = 0.89 (0.82 -0.96), and SA = 0.90 (0.85-0.96). Interobserver reliability is as follows: SI = 0.90 (0.84-0.94), SA = 0.78 (0.64-0.86), and LCEA = 0.73 (0.56-0.82). There were 51 dysplastic hips within this cohort.

Conclusion

The SI is a reproducible measurement on plain radiographs. The SI is a two-dimensional representation of the size of the weight-bearing surface of the acetabulum and could provide an estimation of joint contact pressures. Used with existing measures, the SI may provide a more nuanced understanding of acetabular morphology.

Computer-Aided System Application Value for Assessing Hip Development

Purpose

A computer-aided system was used to semiautomatically measure Tönnis angle, Sharp angle, and center-edge (CE) angle using contours of the hip bones to establish an auxiliary measurement model for developmental screening or diagnosis of hip joint disorders.

Methods

We retrospectively analyzed bilateral hip x-rays for 124 patients (41 men and 83 women aged 20-70 years) who presented at the Affiliated Zhongshan Hospital of Dalian University in 2017 and 2018. All images were imported into a computer-aided detection system. After manually outlining hip bone contours, Tönnis angle, Sharp angle, and CE angle marker lines were automatically extracted, and the angles were measured and recorded. An imaging physician also manually measured all angles and recorded hip development, and Pearson correlation coefficients were used to compare computer-aided system measurements with imaging physician measurements. Accuracy for different angles was calculated, and the area under the receiver operating characteristic (AUROC) curve was used to represent the diagnostic efficiency of the computer-aided system.

Results

For Tönnis angle, Sharp angle, and CE angle, correlation coefficients were 0.902, 0.887, and 0.902, respectively; the accuracies of the computer-aided detection system were 89.1, 93.1, and 82.3%; and the AUROC curve values were 0.940, 0.956, and 0.948.

Conclusion

The measurements of Tönnis angle, Sharp angle, and CE angle using the semiautomatic system were highly correlated with the measurements of the imaging physician and can be used to assess hip joint development with high accuracy and diagnostic efficiency.

How to judge pelvic malposition when assessing acetabular index in children? Three simple parameters can determine acceptability

BACKGROUND

The acetabular index (AI) is the most commonly used parameter for diagnosing hip dysplasia. Pelvic malposition can result in misinterpretation of AI measurement especially in younger children. We aimed to investigate the correlation between pelvic orientation and acetabular index (AI) by using digital reconstructed radiographs (DRRs) and identify reliable parameters predictive of pelvic orientation on plain radiographs.

METHODS

We retrospectively identified 33 children (52 hips) who received dual source CT examinations. Virtual pelvic models were reconstructed after scanning. After orientating in the standard neutral position, the models were rotated and tilted around corresponding axes. DRRs were generated at every 3° during the process. The acetabular index, the horizontal diameter (Dh) and vertical diameter (Dv) of bilateral obturator foramina, the vertical distance (h) between upper border of pubic symphysis, and Hilgenreiner's line were measured on each DRR by two independent observers. Rotation index (Rr = right Dh/left Dh), tilt index (Rt = h/Dv), intra-observer error, and inter-observer error of AI were calculated.

RESULTS

For tilt and rotation up to 12.0°, AI increased with anterior tilt and decreased with posterior tilt. And for rotation, it increased on the side toward which the pelvis rotated and decreased on the opposite side. AI varied dramatically if angulation exceeded 6.0°. Malposition below this limit demonstrated the intra- and inter-observer errors were ± 2.0° and ± 3.0° respectively and caused no significant effect on AI measurement.

CONCLUSIONS

For children up to age 6 years, an acceptable pelvic plain radiograph can be determined when Rt is approximately between 0.9 and 1.4 and Rr between 0.7 and 1.5. For the first time, we have identified parameters derived from a group of subjects which can predict this degree of malposition. The parameters obturator diameters (Dh), obturator height (Dv), and distance (h) between symphysis and Hilgengreiner's line can be feasibly measured on X-ray and employed in clinical practice to assess the acceptability of the pediatric pelvic radiograph prior to measurement of the AI.

San Diego pelvic osteotomy in patients with closed triradiate cartilage

PURPOSE

A San Diego pelvic osteotomy is frequently used as part of the surgical treatment of neuromuscular patients with hip displacement. This short-term follow-up study assesses the effectiveness of this osteotomy in patients with closed triradiate cartilage compared with open triradiates.

METHODS

Retrospective review of 43 patients (44 hips) with neuromuscular hip disease who underwent a San Diego pelvic osteotomy to correct hip displacement. In all 24 hips had open triradiate cartilage at the time of surgery and 20 hips were closed. Centre edge angle (CEA), acetabular angle (AA) and Reimer's index (RI) were recorded from preoperative, postoperative and the latest follow-up radiographs and statistical analysis was performed.

RESULTS

CEA improved by 39° (7° to 69°) in the open group and 30° (9° to 80°) in the closed group from preoperative radiographs to postoperative, with no significant difference in improvement between groups (p = 0.084). There was no significant difference in AA between the open (improved by 11° (3° to 23°)) and closed (improved by 10° (4° to 21°)) groups (p = 0.65). RI improved from 61% to 11% in the open group and 51% to 12% in the closed group. There was no statistically significant difference between groups in RI at preoperative, immediate postoperative and final follow-up radiographs. At latest follow-up, CEA, AA and RI all remained relatively stable in both groups.

CONCLUSIONS

San Diego pelvic osteotomy is equally effective in improving radiographic parameters in neuromuscular patients with both open and closed triradiate cartilage. This study challenges the notion that closed triradiate cartilage is a contraindication to a San Diego pelvic osteotomy.

LEVEL OF EVIDENCE

III.

Do Radiographic Parameters of Dysplasia Improve to Normal Ranges After Bernese Periacetabular Osteotomy?

BACKGROUND

The goal of periacetabular osteotomy (PAO) is to improve the insufficient coverage of the femoral head and achieve joint stability without creating secondary femoroacetabular impingement. However, the complex tridimensional morphology of the dysplastic acetabulum presents a challenge to restoration of normal radiographic parameters. Accurate acetabular correction is important to achieve long-term function and pain improvement. There are limited data about the proportion of patients who have normal radiographic parameters restored after PAO and the factors associated with under- and overcorrection.

QUESTIONS/PURPOSES

(1) What is the proportion of patients undergoing PAO in which the acetabular correction as assessed by the lateral center-edge angle (LCEA), anterior center-edge angle (ACEA), acetabular inclination (AI), and extrusion index (EI) is within defined target ranges? (2) What patient and preoperative factors are associated with undercorrection of the acetabulum as defined by a LCEA < 22°, a factor that has been reported to be associated with PAO failure at 10-year followup?

METHODS

Between January 2007 and December 2011 we performed 132 PAOs in 116 patients for treatment of symptomatic acetabular dysplasia. One patient with Legg-Calvé-Perthes disease, one with multiple osteochondromatosis, and two with concomitant femoral osteotomy were excluded. A total of 128 hips (112 patients) were included. The hip cohort was 76% (97 of 128) female and the mean age at surgery was 28.5 years (SD 8.7 years). Correction of LCEA between 25° and 40°, ACEA between 18° and 38°, Tönnis angle between 0° and 10°, and EI ≤ 20% were defined as adequate based on normative values. Values lower than the established parameters were considered undercorrection for the LCEA and ACEA and those higher than the established values were considered overcorrection. Because postoperative LCEA < 22^o has been previously associated with PAO failure at a minimum of 10-year followup, in this study we sought to measure whether demographic factors including age, gender, body mass index, and severity of acetabular dysplasia assessed by preoperative LCEA, ACEA, AI, and EI were associated with undercorrection. Postoperative radiographs were obtained at minimum of 1 month after surgery (mean, 7 months; range, 1-44 months) and were measured by a professional research assistant and a hip reconstruction fellow not involved in the clinical care of the patients. No patient was lost to followup.

RESULTS

Of the 128 hips, the proportion of hips with radiographic parameters within the established range was 78% (100 hips) for the LCEA, 86% (110 hips) for the ACEA, 89% (114 hips) for the AI, and 80% (102 hips) for the EI. For hips with an inadequate correction, the LCEA was more often undercorrected than overcorrected (20% versus 2%; 95% confidence interval [CI], 11%-27%; p < 0.001), whereas the ACEA was more often overcorrected than undercorrected (11% versus 3%; 95% CI, 1%-15%; p = 0.03) After adjusting for age, sex, body mass index, and preoperative radiographic parameters including ACEA, AI, and EI, we found that the preoperative LCEA was the only independent factor associated with a postoperative LCEA < 22° (odds ratio, 0.92; 95% CI, 0.87-0.97; p = 0.003), indicating that hips with lower preoperative LCEA were more likely to have a LCEA < 22°. For each additional degree of preoperative LCEA, the odds of LCEA < 22° were reduced by 15%.

CONCLUSIONS

Acetabular correction after PAO performed by two experienced surgeons was adequate for individual radiographic parameters in most but not all hips. Hips with more severe dysplasia preoperatively are at higher risk for undercorrection as assessed by the LCEA. This intuitive information may help surgeons performing PAO in severely dysplastic hips plan for possible combined procedures including a femoral osteotomy if PAO alone does not allow for adequate correction of femoral head coverage and a congruous concentric hip. Further studies are planned to determine whether the long-term hip function and pain in patients whose hips were corrected within these established parameters will be improved in comparison to those that were under- or overcorrected.

LEVEL OF EVIDENCE

Level III, therapeutic study.

A novel computer-based method for measuring the acetabular angle on hip radiographs

Objective

The aim of this study was to propose a new computer based method for measuring acetabular angles on hip radiographs and to assess its practicality, sensitivity and reliability for acetabular angle measurement.

Methods

A total of 314 acetabulum were assessed on 157 pelvic X-ray images. Acetabular angles were measured with both the conventional method (Method 1) and our proposed method (Method 2). All the Acetabular Index (AI) angle, Acetabular Angle (AA) and Acetabular Center (ACM) angle were measured with both methods.

Results

The mean AI angle for Method 1 is 11.02° ± 2.7° and the mean AI angle for Method 2 is 10.08° ± 1.88°, the mean AA angle for Method 1 is 39.5° ± 5.3° and the mean AA angle for Method 2 is 39.36° ± 4.68°, the mean ACM angle for Method 1 is 50.5° ± 6.01° and the mean ACM angle for Method 2 is 55.42° ± 12.43°.

Conclusion

Our novel automated method appear to be reliable and practical for acetabular angle measurement on hip radiographs.

Level of Evidence

Level III, Diagnostic study

Postoperative Imaging in the Setting of Hip Preservation Surgery

Osteoarthritis of the hip remains a prevalent disease condition that influences ever-changing treatment options. Procedures performed to correct anatomic variations, and, in turn, prevent or slow the progression of osteoarthritis, are aptly referred to as types of hip preservation surgery (HPS). Conditions that predispose individuals to femoroacetabular impingement (FAI), including pincer- and cam-type morphology, and hip dysplasia are specifically targeted in HPS. Common surgical interventions include acetabuloplasty, osteochondroplasty, periacetabular osteotomy (PAO), and derotational femoral osteotomy (DFO). The radiologist's understanding of the surgical approach, pre- and postoperative imaging findings, and common complications of HPS are paramount to providing value to the patient and surgeon. Acetabuloplasty and osteochondroplasty are performed to address pincer- and cam-type morphology in patients with FAI. With both of these HPS techniques, the goal is to restore the normal morphology by resecting excess bone in the acetabulum or femoral head or neck. As a result, a frequently encountered complication is incomplete or excessive resection. Excessive resection can predispose the patient to dislocation in the case of acetabuloplasty and fracture in the case of osteochondroplasty. Iatrogenic injury to adjacent structures such as the ischiofemoral ligament and acetabular cartilage also may occur. Although rare, especially when an arthroscopic approach is used, avascular necrosis remains a risk. Femoral head undercoverage in hip dysplasia is corrected by using PAO, which may be performed as the sole procedure or in conjunction with DFO. Incomplete or excessive rotation during surgery can result in postprocedural complications. As with any orthopedic procedure involving osteotomy, nonhealing is a risk. Iatrogenic injury in the form of fracture or hardware failure also may be seen. ^©RSNA, 2016.

Defining the lateral edge of the femoroacetabular articulation: correlation analysis between radiographs and computed tomography

PURPOSE

The purpose of this study was to analyze the variation in measuring the lateral center edge angle of Wiberg (LCEA) using the lateral edge of the sourcil (LCEA-S) compared to the lateral edge of the acetabulum (LCEA-E), and to correlate these measurements with three-dimensional computed tomography (3D-CT)-based analysis of the femoroacetabular articulation.

METHODS

A retrospective analysis was performed on 24 patients (45 hips) treated for hip dysplasia at a single institution. All patients were required to have an anteroposterior (AP) pelvis radiograph and pelvic CT. LCEA-S and LCEA-E measurements were calculated from radiographs. Axial CT images were processed to standardize pelvic orientation and calculate the LCEA at three points (posterior, central, anterior) along the acetabular edge. Correlation analysis was used to evaluate radiographic and CT measures.

RESULTS

Eight males and 16 females with an average age of 14.6 years were included. The LCEA-S (16.5° ± 2.0°) was found to be significantly less than the LCEA-E (26.0° ± 2.0°) (p < 0.001). The LCEA-S had the greatest correlation with the central measurement on the 3D-CT (r s = 0.893; p < 0.001). The LCEA-E had the greatest correlation with the anterior measurement on the 3D-CT (r = 0.834; p < 0.001).

CONCLUSIONS

The LCEA can change significantly depending on the bony landmark used to define the lateral edge of the femoroacetabular articulation. The edge of the sourcil most closely correlates with the central weight-bearing portion of the articular surface on the 3D-CT and should be used to define the LCEA when treating patients with hip dysplasia.

LEVEL OF EVIDENCE

Level III, retrospective comparison study.

Toward automated classification of acetabular shape in ultrasound for diagnosis of DDH: Contour alpha angle and the rounding index

BACKGROUND AND OBJECTIVES

The diagnosis of Developmental Dysplasia of the Hip (DDH) in infants is currently made primarily by ultrasound. However, two-dimensional ultrasound (2DUS) images capture only an incomplete portion of the acetabular shape, and the alpha and beta angles measured on 2DUS for the Graf classification technique show high inter-scan and inter-observer variability. This variability relates partly to the manual determination of the apex point separating the acetabular roof from the ilium during index measurement. This study proposes a new 2DUS image processing technique for semi-automated tracing of the bony surface followed by automatic calculation of two indices: a contour-based alpha angle (αA), and a new modality-independent quantitative rounding index (M). The new index M is independent of the apex point, and can be directly extended to 3D surface models.

METHODS

We tested the proposed indices on a dataset of 114 2DUS scans of infant hips aged between 4 and 183 days scanned using a 12MHz linear transducer. We calculated the manual alpha angle (αM), coverage, contour-based alpha angle and rounding index for each of the recordings and statistically evaluated these indices based on regression analysis, area under the receiver operating characteristic curve (AUC) and analysis of variance (ANOVA).

RESULTS

Processing time for calculating αA and M was similar to manual alpha angle measurement, ∼30s per image. Reliability of the new indices was high, with inter-observer intraclass correlation coefficients (ICC) 0.90 for αA and 0.89 for M. For a diagnostic test classifying hips as normal or dysplastic, AUC was 93.0% for αA vs. 92.7% for αM, 91.6% for M alone, and up to 95.7% for combination of M with αM, αA or coverage.

CONCLUSIONS

The rounding index provides complimentary information to conventional indices such as alpha angle and coverage. Calculation of the contour-based alpha angle and rounding index is rapid, shows potential to improve the reliability and accuracy of DDH diagnosis from 2DUS, and could be extended to 3D ultrasound in future.

Which radiographic hip parameters do not have to be corrected for pelvic rotation and tilt?

BACKGROUND

Acetabular anatomy on AP pelvic radiographs depends on pelvic orientation during radiograph acquisition. However, not all parameters may change to a clinically relevant degree with differences in pelvic orientation. This issue may influence the diagnosis of acetabular pathologies and planning of corrective acetabular surgery (reorientation or rim trimming). However, to this point, it has not been well characterized.

QUESTIONS/PURPOSES

We asked (1) which radiographic parameters change in a clinical setting when normalized to neutral pelvic orientation; (2) which parameters do not change in an experimental setting when the pelvis is experimentally rotated/tilted; and (3) which of these changes are "ultimately" relevant based on a prespecified definition of relevance.

METHODS

In a clinical setup, 11 hip parameters were evaluated in 101 patients (126 hips) by two observers and the interobserver difference was calculated. All parameters were normalized to an anatomically defined neutral pelvic orientation with the help of a lateral pelvic radiograph and specific software. Differences between nonnormalized and normalized values were calculated (effect of normalization). In an experimental setup involving 20 cadaver pelves (40 hips), the maximum range for each parameter was computed with the pelvis rotated (range, -12° to 12°) and tilted (range, -24° to 24°). "Ultimately" relevant changes existed if the effect of normalization exceeded the interobserver difference (eg, 37% versus 6% for prevalence of a positive crossover sign) and/or the maximum experimental range exceeded 1 SD of interobserver difference (eg, 27% versus 6% for anterior acetabular coverage).

RESULTS

In the clinical setup, all parameters except the ACM angle and craniocaudal acetabular coverage changed when being normalized, eg, effect of normalization for lateral center-edge angle, acetabular index, and sharp angle ranged from -5° to 4° (p values < 0.029). In the experimental setup, five parameters showed no major changes, whereas six parameters did change (all p values < 0.001). Ultimately relevant changes were found for anteroposterior acetabular coverage, retroversion index, and prevalence of a positive crossover or posterior wall sign.

CONCLUSIONS

Lateral center-edge angle, ACM angle, Sharp angle, acetabular and extrusion index, and craniocaudal acetabular coverage showed no relevant changes with varying pelvic orientation and can therefore be acquired independent from individual pelvic tilt and rotation in clinical practice. In contrast, anteroposterior acetabular coverage, crossover and posterior wall sign, and retroversion index call for specific efforts that address individual pelvic orientation such as computer-assisted evaluation of radiographs.

Ultrasound quantification of acetabular rounding in hip dysplasia: reliability and correlation to treatment decisions in a retrospective study

Currently, acetabular rounding is only subjectively assessed on ultrasound for developmental dysplasia of the hip. We tested whether acetabular rounding can be quantified reliably and can distinguish between hips requiring and not requiring treatment. Consecutive infants (n = 90) suspected of having dysplasia of the hip, seen at a pediatric orthopedic clinic, were separated into four diagnostic categories (normal, borderline but resolved, treated by brace, treated surgically). Acetabular rounding was assessed by semi-quantitative grade (0 = nil, 1 = mild, 2 = moderate, 3 = severe) by three observers and by direct measurement of acetabular radius of curvature (AROC) by two observers. Inter-observer reliability of rounding grade was poor (κ = 0.30-0.37). AROC had an inter-observer intra-class correlation coefficient of 0.84 and coefficient of variation of 29%-34%. Mean AROC was significantly higher for hips requiring treatment than for those not requiring treatment (3.3 mm vs. 1.6 mm, p = 0.007). AROC reliably quantifies an observation currently being made subjectively by radiologists and surgeons, and may be useful as a supplementary ultrasound index of dysplasia of the hip in future prospective studies.

Radiographic measurements of hip dysplasia at skeletal maturity--new reference intervals based on 2,038 19-year-old Norwegians

OBJECTIVE

Normative references for radiographic measurements commonly used in the diagnosis of developmental dysplasia of the hip at skeletal maturity are incomplete. The present study therefore aimed to establish new gender-specific standards for measurements reflecting the acetabular morphology, namely Sharp's angle, the acetabular roof angle of Tönnis (AA) and the acetabular depth-width ratio (ADR), and measurements reflecting the position of the femoral head related to the acetabulum, namely the center-edge (CE) angle of Wiberg, the refined CE angle of Ogata, and the femoral head extrusion index (FHEI). The joint space width (JSW) is also reported.

MATERIALS AND METHODS

The population-based 1989 Bergen Birth Cohort (n = 3,935) was invited at age 19 years to a follow-up during 2007-09, of which 2,038 (52 %) attended. A standardized antero-posterior radiograph was assessed. The normative references are presented as mean ± standard deviation (SD) and 2.5-97.5 percentiles with 95 % confidence intervals.

RESULTS

A total of 2,011 (841 males, 1,170 females, mean age 18.6 (SD 0.6)) radiographs were analyzed. Sharp's angle was 38.8° ± 3.5° in males and 40.7° ± 3.5° in females, with 97.5 percentiles of 46° and 47°, respectively. The CE angle was 32.1° ± 6.1° in males and 31.0° ± 6.1° in females, with 2.5 percentiles of 21° and 20°, respectively. The FHEI was 86.0 % ± 6.3 % in males and 85.6 % ± 6.6 % in females, with 2.5 percentiles of 74° and 73°, respectively.

CONCLUSIONS

Updated gender-specific reference ranges for radiographic measurements commonly used for hip dysplasia at skeletal maturity are reported, similar to or slightly wider than those described in the literature. Statistically significant gender differences have been confirmed for most of the measurements.

Do fluoroscopy and postoperative radiographs correlate for periacetabular osteotomy corrections?

BACKGROUND

The Bernese periacetabular osteotomy (PAO) can relieve pain and restore function in patients with symptomatic acetabular dysplasia. Accurate acetabular correction is fundamental to achieving these clinical goals and presumably enhancing survivorship of the reconstruction. Fluoroscopy is used by some surgeons to assess intraoperative acetabular correction but it is unclear whether the features observed by fluoroscopy accurately reflect those on postoperative radiographs.

QUESTIONS/PURPOSES

We therefore determined whether the parameters of acetabular correction of PAO correlated on intraoperative fluoroscopic imaging and postoperative radiography.

METHODS

We retrospectively reviewed the imaging of 48 patients (50 hips) who underwent PAO. Intraoperative fluoroscopic AP and false profile images were obtained after final PAO correction. The intraoperative deformity correction as measured on the two fluoroscopy views was compared with the correction determined with postoperative standing plain AP pelvis and false profile radiographs using common measurements of acetabular position.

RESULTS

Of all radiographic parameters, lateral center-edge angle had the highest correlation between intraoperative fluoroscopy and the postoperative radiograph with an intraclass correlation coefficient (ICC) of 0.80 (0.68-0.88). Similarly, acetabular inclination and anterior center-edge angle also correlated with ICCs of 0.76 (0.61-0.85) and 0.71 (0.54-0.82), respectively. Extrusion index and medial offset distance had lower correlations with ICCs of 0.66 (0.46-0.79) and 0.46 (0.21-0.65), respectively.

CONCLUSIONS

Intraoperative fluoroscopic assessment of PAO correction correlated with that from the postoperative radiographic assessment. Measurement of lateral center-edge angle shows the highest correlation with the fewest outliers. Acetabular inclination and anterior center-edge angle also correlated; extrusion index and medial offset distance should be used with more caution.

Bosworth hip shelf arthroplasty in adult dysplastic hips: ten to twenty three year results

PURPOSE

Hip shelf arthroplasty is currently considered to be a salvage procedure. The aim of the study is to present outcomes of Bosworth hip shelf arthroplasty in adolescent dysplastic hips with a minimum ten-year follow-up.

METHODS

The basic group comprised 25 hips in 18 patients with the mean age of 31 years (range, 16-52) at the time of operation. Subgroup A included 20 hips that were evaluated prior to operation as spherical, centric hips without osteoarthritic changes (acetabular dysplasia). The heterogeneous subgroup B comprised five hips. Of these, three hips were evaluated as aspheric, without osteoarthritic changes, and two hips as aspheric, with osteoarthritic changes of grade 2 according to Tönnis. In addition, two hips in subgroup B were evaluated as decentred (subluxated), one hip without and one hip with osteoarthritic changes. The mean follow-up was 15 years (range, ten-23).

RESULTS

In subgroup A, the positive effect of operation had lasted at the time of the final follow-up for ten to 22 years postoperatively (average follow-up 14 years) in 19 hips. Only one female patient, 46 years old at the time of operation, developed hip osteoarthritis within ten years, that was treated by THA. In subgroup B, a lasting positive effect of operation was recorded in two cases at the time of the final follow-up (12 and 15 years). The third female patient with an aspheric and decentred hip developed severe hip osteoarthritis 21 years after shelf procedure that was treated by THA. In two patients who had hip osteoarthritis already before the operation, the positive effect of the shelf procedure survived over 13 and 20 years. Although hip osteoarthritis progressed, THA was performed as late as 15 and 23 years after the shelf procedure. The mean Harris hip score in 21 hips with a still functional hip shelf was 68 (range, 56-82) before and 90 (range, 76-100) after the surgery.

CONCLUSION

The best outcomes of Bosworth hip shelf arthroplasty may be expected in a dysplastic spherical centred hip without osteoarthritic changes. In the presence of asphericity, decentration and osteoarthritic changes, neither the effect of the surgery nor its survival can be clearly predicted.