Can experts in acetabular fracture care determine hip stability after posterior wall fractures using plain radiographs and computed tomography?

Using an Intraoperative Stress Examination to Direct Treatment in Posterior Femoral Head Fracture-Dislocations

OBJECTIVE

To examine the results of a treatment algorithm incorporating an examination under anesthesia (EUA) performed intraoperatively after fixation of the femoral head through a Smith-Petersen approach to determine the need for posterior wall or capsule repair.

METHODS

DESIGN

Retrospective review.

SETTING

Two Level 1 trauma centers.

PATIENT SELECTION CRITERIA

All acute, traumatic femoral head fractures from posterior hip dislocations treated at participating centers over a 5-year period from 2017 to 2022. Injuries were classified according to the Pipkin system.

OUTCOME MEASURES AND COMPARISONS

The primary outcome was the result of intraoperative EUA performed after femoral head fixation to determine the need for Kocher-Langenbeck exposure for posterior wall and/or capsule fixation. The secondary outcomes included rates of avascular necrosis, heterotopic bone formation, late instability, and conversion to total hip arthroplasty (THA).

RESULTS

In total, 63 men and 22 women with a mean age of 32.5 (range 18-71) years were studied. Seventy-nine of 85 (92.9%) patients had a stable EUA after fixation of the femoral head through a Smith-Petersen approach. Six (6/85, 7.1%) underwent an additional Kocher-Langenbeck approach for posterior wall or capsule fixation. This included 1 Pipkin I, 1 Pipkin II, and 4 Pipkin IV injuries. Of the Pipkin IV injuries, 51/55 (92.7%) had stable EUA and did not require fixation of their posterior wall. This included seven patients with wall involvement >20%. Five patients were excluded because of planned fixation of their posterior wall based on preoperative imaging. Of patients with at least 6 months follow-up, 16 of 65 (26.4%) developed radiographic evidence of avascular necrosis and 21 of 65 (32.3%) evidence of heterotopic bone formation. Seven out of 65 (10.8%) were converted to THA over the study period. When comparing patients with a single exposure and those with additional KL exposure, it was found that they did not vary in their rate of avascular necrosis (27.1% vs. 0.0%, P = 0.3228), heterotopic ossification formation (30.5% vs. 50.0%, P = 0.3788), or conversion to THA (10.2% vs. 16.7%, P = 0.510).

CONCLUSIONS

This study found residual posterior hip instability after femoral head fixation in patients with and without posterior wall fractures after posterior dislocations. The results of this study support the use of an EUA after femoral head fixation to identify residual posterior hip instability in all femoral head fractures from posterior hip dislocations, regardless of Pipkin type. Use of the Smith-Petersen exposure remains a viable surgical option and may be improved with the incorporation of an EUA after femoral head fixation. For Pipkin IV injuries with posterior wall fractures with indeterminate stability, an EUA accurately identifies residual instability.

LEVEL OF EVIDENCE

Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Assessment of Force Applied During Examination Under Anesthesia Used to Determine Stability in Posterior Wall Acetabular Fractures

OBJECTIVES

Determination of hip instability associated with posterior wall acetabular fractures may be difficult. Thus, dynamic stress examination under anesthesia (EUA) was developed as a tool for guiding treatment. EUA uses positioning of the hip and application of force across the hip to detect instability. While aspects of the EUA technique seems consistently described in the literature and practiced by surgeons, some components are ill-defined. The goal of this study was to assess standardization of applied force during EUA among experienced acetabular surgeons.

METHODS

Fellowship-trained orthopaedic trauma surgeons with experience in acetabular fracture treatment performed EUA for posterior wall instability on an intact, fresh human cadaver. All surgeons used a similar method, and each expert performed EUA multiple times separated by a brief hiatus. The maximum force applied along the femur's vector in Newtons (N) was measured using a hand-held digital dynamometer.

RESULTS

The EUAs of 19 surgeons were evaluated. Five surgeons had been practicing for <5 years, six for 6 to 10 years, five for 11 to 20 years, and three for >20 years. The mean force applied during EUA was 173N, with a notable variability between surgeons (range, 77-368N). Notable variability was also observed between sequential measures of individual surgeons with six surgeons (31.6%) having a >50N range on repeat trials.

CONCLUSION

This is the first study to report force applied during an EUA to assess for posterior wall acetabular fracture stability. Notable variability was observed among surgeons performing the examination and in repeated examinations by the same surgeon, suggesting that results of EUA may be surgeon-dependent. Further study is needed to determine what optimal applied force should be used to assess hip stability after a posterior wall acetabular fracture.

LEVEL OF EVIDENCE

Level V. An assessment of a diagnostic tool.

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.

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.

A New Computed Tomography-Based Measure that Provides Insight Into Hip Stability in Patients With Posterior Wall Acetabular Fractures

OBJECTIVES

To describe the technique and results of a new sagittal plane computed tomography (CT)-based angular measure for predicting stability after posterior wall acetabular fractures (PWF).

METHODS

DESIGN

Retrospective review.

SETTING

Academic Level II trauma center.

PATIENT SELECTION CRITERIA

Fifty-eight consecutive patients with PWF (AO/OTA class 62A.1), 98% were high-energy injuries.

INTERVENTION

A new sagittal CT measure of PWF based on the angle subtending the joint center, cranial and caudal fracture exits.

OUTCOME MEASURES AND COMPARISONS

Hip incongruity or dislocation demonstrated using gold standard test, examination under anesthesia (EUA), or instability on static images. Prediction of hip instability using a sagittal CT angular measure based on cranial and caudal fracture exits was compared with previous axial CT measures suggestive of increased risk for instability including posterior wall size >50%, and those with cranial exit within 5.0 mm of the acetabular dome.

RESULTS

There were 32 operative and 26 nonoperatively treated fractures. Thirty fractures were determined to be unstable, and 28 were stable after EUA. Measurements of >70 degrees using the sagittal CT angular measure predicted instability in 28 of 28 patients, and ≤70 degrees predicted stability in 30 of 30 patients (sensitivity 100% and specificity 100%). Prevalence of EUA confirmed instability for subgroups with PWF based on prior axial CT measures were as follows: ≥50% wall involvement (11/16; sensitivity 67% and specificity 60%; 95% CI, 45%-89%/45%-75%), fracture within 5.0 mm of dome (5/18; sensitivity 86% and specificity 73%; 95% CI, 71%-100%/59%-87%), fracture within 5.0 mm of dome and ≥50% involvement (1/9; sensitivity 89% and specificity 56%; 95% CI, 69%-100%/24%-88%).

CONCLUSIONS

In a sample of 58 mostly high energy posterior wall fractures all having had an EUA, a new sagittal angular CT measurement of ≤70 degrees predicted hip stability and >70 degrees predicted instability with 100% sensitivity and specificity.

LEVEL OF EVIDENCE

Diagnostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Evaluating the utility of post-reduction imaging for simple hip joint dislocations: Is computed tomography always necessary?

Introduction

Following closed reduction of hip dislocations, computed tomography (CT) is considered standard of care to identify occult fractures or intra-articular loose bodies that may be missed on X-ray. The purpose of this study was to evaluate the sensitivity of post-reduction X-rays and the usefulness of subsequent post-reduction CT imaging.

Methods

All patients presenting to our hospital system for traumatic hip dislocations from 2013 to 2022 were retrospectively reviewed. Participants were included if they had a simple dislocation of a native hip, underwent closed reduction, and received post-reduction X-ray and CT imaging. A sensitivity analysis was performed for the detection of associated fractures and intraarticular loose bodies by post-reduction X-ray, using CT as a reference standard.

Results

Thirty-five subjects with a mean age of 26 years were included. Post-reduction CT revealed 6 fractures and 3 loose bodies, whereas post-reduction X-ray identified 3/6 (50%) fractures and 3/3 (100%) loose bodies. Four cases received operative management, all of which were identified by X-ray. Post-reduction X-ray had a sensitivity of 67% for identifying pathology that was subsequently found on CT, and a sensitivity of 100% for identifying pathology requiring surgery. Of the 13 cases with pre-reduction CT scans, none had new findings identified on post-reduction CT.

Conclusions

Post-reduction X-rays are effective in the evaluation of acute pathology associated with closed reduction of traumatic hip dislocations, especially for cases requiring operative management. Our findings suggest that if a fracture or loose body was not identified on post-reduction X-ray, a post-reduction CT added no value in surgical decision-making and was not necessary.

Surgeon Accuracy in Prediction of Stability of Posterior Wall Acetabular Fractures. A Survey of Orthopaedic Trauma Surgeons

OBJECTIVES

This study aims to investigate surgeon accuracy in prediction of the stability of posterior wall acetabular fractures by comparing "examination under anesthesia" findings to submitted estimations on the basis of radiograph and computed tomography (CT) imaging across a range of experience in orthopaedic surgeons and trainees.

METHODS

Records of patients who underwent examination under anesthesia after presenting with posterior wall acetabular fractures at 2 different institutions were pooled for data collection, totaling 50 cases. Radiographs, CT images, and information regarding the presence of a hip dislocation requiring procedural reduction were provided to participants for review. A survey was generated for submission of impressions of stability for each individual case and disseminated among orthopaedic trainees and surgeons in practice.

RESULTS

The submissions of 11 respondents were analyzed. Mean accuracy was calculated to be 0.70 (SD = 0.07). Sensitivity and specificity of respondents were 0.68 (SD = 0.11) and 0.71 (SD = 0.12), respectively. Positive predictive value and negative predictive value for respondents were 0.56 (SD = 0.09) and 0.82 (SD = 0.04), respectively. There was poor correlation of accuracy with years of experience with R 2 calculated to be 0.0004 and poor agreement between observers with Kappa measurement of interobserver reliability of 0.46.

CONCLUSIONS

Our study suggests that surgeons are unable to consistently differentiate between stable and unstable patterns on the basis of assessments based on x-ray and CT. Years of experience in training or practice was not found to be associated with improved accuracy of stability prediction.

Low interobserver and intraobserver reliability using the Matta radiographic system for intraoperative assessment of reduction following acetabular ORIF

INTRODUCTION

The system described by Matta for rating acetabular fracture quality of reduction following ORIF has been used extensively throughout the literature. However, the reliability of this system remains to be validated. We sought to determine the interobserver and intraobserver reliability of this system when used by fellowship-trained pelvic and acetabular surgeons to evaluate intraoperative fluoroscopy.

METHODS

This is a retrospective evaluation of a prospectively collected acetabular fracture database at an academic level I trauma center. The quality of reduction of all acetabular fractures treated with open reduction internal fixation (ORIF) between May 2013 and December 2015 was assessed using three standard intraoperative fluoroscopic views (anteroposterior and two 45˚ oblique Judets). Displacement of ≤1 mm was considered to be an anatomic reduction, 2-3 mm imperfect, and >3 mm poor according to the system described by Matta. A total of 107 acetabular fractures treated with ORIF with complete intraoperative fluoroscopic images during that time period were available for review. Acetabular fracture reductions were reviewed by the operative surgeon at the time of surgery and subsequently reviewed by two fellowship-trained pelvic and acetabular surgeons. All reduction assessments were performed in a blinded fashion. The primary outcome measure was interobserver reliability for assessing reduction quality. This was evaluated using a weighted kappa (κ_w) statistic between each evaluator and the operative surgeon and a generalized kappa (κ_g) for all 3 surgeons. After a 6-week "washout interval," the surgeons reviewed the images again and intraobserver agreement was calculated using a weighted kappa statistic.

RESULTS

Interobserver reliability based on the initial assessment was low (κ_g = 0.09); however, did slightly improve with the second assessment to fair (κ_g = 0.24). Intraobserver reliability ranged from slight (κ_w = 0.20) to moderate (κ_w = 0.53) among the surgeons.

DISCUSSION

Low interobserver and intraobserver reliability was found when quality of reduction was assessed with intraoperative fluoroscopic images by the operative and two other pelvic and acetabular surgeons using the Matta system. Given the importance of an anatomic reduction on functional and radiographic outcomes, an accurate and reliable system for assessing intraoperative quality of reduction is essential.

Nonoperative Treatment of Posterior Wall Acetabular Fractures After Dynamic Stress Examination Under Anesthesia: Revisited

OBJECTIVES

Performing an examination under general anesthesia (EUA) using dynamic stress fluoroscopy of patients with posterior wall acetabular fractures has been used as a tool to determine hip stability and the need for surgical intervention. The purpose of this study was to further evaluate the effectiveness of this technique, from a source other than its primary advocates, in patients with posterior wall acetabular fractures less than or equal to 50% who were stable on EUA and treated nonoperatively.

DESIGN

Retrospective case series.

SETTING

University Level 1 Trauma Center.

PARTICIPANTS

Seventeen patients with a posterior wall acetabular fracture stable on EUA treated nonoperatively.

INTERVENTION

The patients were treated nonoperatively as guided by an EUA negative for instability. Patient follow-up averaged 30 months (range, 6-64 months).

MAIN OUTCOME MEASUREMENTS

Outcome evaluation included the modified Merle d'Aubigné clinical score and the Short Musculoskeletal Function Assessment Questionnaire. Radiographic evaluation for subluxation or arthritis consisted of the 3 standard pelvic radiographs.

RESULTS

Radiographic evaluation showed all hips to be congruent with a normal joint space. Sixteen of the 17 patients had radiographic outcomes rated as "excellent"; 1 patient was rated "good." The modified Merle d'Aubigné score (obtained in 12 patients) averaged very good, with only 1 having less than a good (graded as fair) clinical outcome. The Short Musculoskeletal Function Assessment Questionnaire scores (from 11 patients) were not significantly different from normal and were within the normal reported values for all indices and categories. There was no correlation between fracture fragment size and outcome.

CONCLUSIONS

This study further supports the contention that a stable hip joint, as determined by EUA, after posterior wall acetabular fracture treated nonoperatively is predictive of continued joint congruity, an excellent radiographic outcome, and good-to-excellent early clinical and functional outcomes.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Evaluation and Management of Posterior Wall Acetabulum Fractures

Posterior wall acetabulum fractures typically result from high-energy mechanisms and can be associated with various orthopaedic and nonorthopaedic injuries. They range from isolated simple patterns to multifragmentary with or without marginal impaction. Determination of hip stability, which can depend on fragment location, size, and displacement, directs management. Although important in the assessment of posterior wall fractures, CT is unreliable when used to determine stability. The dynamic fluoroscopic examination under anesthesia (EUA) is the benchmark in assessment of hip stability, and fractures deemed stable by EUA have good radiographic and functional outcomes. In fractures that meet surgical criteria, accurate joint reduction guides outcomes. Joint débridement, identification and elevation of impaction, and adjunctive fixation of posterosuperior and peripheral rim fragments along with standard buttress plate fixation are critical. Complications of the fracture and surgical fixation include sciatic nerve injury, posttraumatic osteoarthritis, osteonecrosis of the femoral head, and heterotopic ossification. Although accuracy of joint reduction is paramount for successful results, other factors out of the surgeon's control such as comminution, femoral head lesions, and dislocation contribute to poor outcomes. Even with anatomic restoration of the joint surface, good clinical outcomes are not guaranteed and residual functional deficits can be expected.

Size and location of posterior wall fragment on CT can predict hip instability in a cadaveric model

PURPOSE

Previous research has been unable to elucidate the exact factors that contribute to hip instability in the setting of posterior wall acetabular fractures. The purpose of this study was to determine the influence of posterior wall fracture fragment size and fracture angle on the stability of the hip joint in a cadaveric model.

METHODS

Six fresh human cadavers (12 hips) were used. Specimens underwent pre-procedure CT evaluation and were then randomized to one of three groups: posterior wall fragment size (FS) of 15%, 20% and 25%. Osteotomies were performed starting at a fracture angle (FA) of 40°. The specimens underwent an exam under anesthesia (EUA). If the hip remained stable, the fracture angle was increased in 20° increments and re-tested until it became unstable.

RESULTS

In the group with a FS of 15%, all hips were stable with a FA of 40°. Increasing the FA to 60° caused all hips to be unstable (subluxation or dislocation). In the group with a FS of 20% and 25%, all hips were unstable with a FA of 40°.

CONCLUSION

In all specimens, a FS of 15% and FA of 40° were stable on EUA. Varying combinations of increasing FS size and increasing FA were all unstable. This study provides data for a CT-based measurement to predict hip instability in the setting of posterior wall acetabular fractures based on FS and FA. More research is required to validate this data in a clinical setting.

Examination Under Anesthesia Improves Agreement on Mechanical Stability: A Survey of Experienced Pelvic Surgeons

OBJECTIVES

To assess agreement among experts in pelvic fracture management regarding stability and need for operative repair of lateral compression-type pelvic fractures with static radiographs compared to static radiographs and examination under anesthesia (EUA).

SETTING

Online survey.

PATIENTS/PARTICIPANTS

Ten patients who presented to our level-1 trauma center with a pelvic ring injury were selected. Vignettes were distributed to 11 experienced pelvic surgeons.

INTERVENTION

Examination under anesthesia.

MAIN OUTCOME MEASUREMENTS

Agreement regarding pelvic fracture stability and need for surgical fixation.

RESULTS

Agreement on stability was achieved in 4 (40%) cases without EUA compared to 8 (80%) cases with EUA. Interreviewer reliability was poor without EUA and moderate with EUA (0.207 vs. 0.592). Agreement on need to perform surgery was achieved in 5 (50%) cases compared to 6 (60%) cases with EUA. Interreviewer reliability was poor without EUA and moderate with EUA (0.250 vs. 0.432). For reference cases with agreement, surgeons were able to predict stability or instability using standard imaging in 57 of a possible 88 reviewer choices (64.8%) compared to 82 of 88 choices (93.2%) with the addition of EUA (P < 0.0001).

CONCLUSIONS

EUA increased agreement among experienced pelvic surgeons regarding the assessment of pelvic ring stability and the need for operative intervention. Further research is necessary to define specific indications for which patients may benefit from EUA.

Posterior wall acetabular fracture in a 13-year-old boy treated by open reduction and mini-plate internal fixation: long-term follow-up of 17 years

BACKGROUND

Acetabular fractures are uncommon in children and adolescents, mainly because of predominant cartilaginous component and strong surrounding ligaments. Although acetabular fractures at this age can lead to significant disability, there is no consensus regarding management, which continues to be controversial. Particularly, long-term outcome after operative management has not been evaluated.

CASE PRESENTATION

We report a case of a 13-year-old boy skeletally immature who presented with an isolated acetabular fracture involving the posterior wall secondary to a traumatic hip dislocation. A Kocher-Langenbeck approach with a surgical luxation of the hip was used for reduction and mini-plate internal fixation of the fracture. Long-term (17-year) follow-up showed a good clinical outcome and a good congruence of the. The patient has bilateral beginning osteoarthritis due to a cam configuration of both hips CONCLUSION: We describe a case of successful operative management of an acetabulum fracture in a skelettaly immature child with a long-term follow-up. Aggressive management of this rare type of fractures may lead to durable positive outcome.

A Survey to Assess Agreement Between Pelvic Surgeons on the Outcome of Examination Under Anesthesia for Lateral Compression Pelvic Fractures

OBJECTIVES

To assess agreement among pelvic surgeons regarding the interpretation of examination under anesthesia (EUA), the methodology by which EUA should be performed, and the definition of a positive examination.

DESIGN

Survey.

PATIENTS/PARTICIPANTS

Ten patients who presented to our Level 1 trauma center with a pelvic ring injury were selected as clinical vignettes. Vignettes were distributed to 15 experienced pelvic surgeons.

INTERVENTION

Examination under anesthesia.

MAIN OUTCOME MEASUREMENTS

Agreement regarding pelvic fracture stability (defined as >80% similar responses), need for surgical fixation, definition of an unstable EUA, and method of performing EUA.

RESULTS

There was agreement that a pelvic fracture was stable or unstable in 8 (80%) of 10 cases. There was agreement that fixation was required or not required in 6 (60.0%) of 10 cases. Seven (46.7%) surgeons endorsed performing a full 15-part EUA, whereas the other 8 (53.3%) used an abbreviated or alternative method. Eight (53.3%) surgeons provided a definition of what constitutes a positive EUA, whereas the remaining 7 did not endorse adhering to a strict definition.

CONCLUSIONS

Pelvic surgeons generally agree on what constitutes a positive or negative EUA but not necessarily the implications of a positive or negative examination. There is no clear consensus among surgeons regarding the method of performing EUA nor regarding the definition of a positive EUA.

LEVEL OF EVIDENCE

Prognostic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Acetabular Fractures in Children and Adolescents: Comparison of Isolated Acetabular Fractures and Acetabular Fractures Associated With Pelvic Ring Injuries

OBJECTIVES

To compare mechanism of injury, fracture pattern, displacement, clinical, and radiographic outcome of isolated acetabular fractures (group 1) versus acetabular fractures associated with a pelvic ring injury (group 2).

DESIGN

Retrospective cohort comparative analysis.

SETTING

Private orthopaedic practice associated with a level one teaching trauma center.

MAIN OUTCOME MEASUREMENTS

Mechanism of injury, fracture pattern, displacement and treatment, Glasgow Coma Scale, Injury Severity Score, leg length discrepancy (LLD), and hip dysplasia.

PATIENTS

Thirty-two children (group 1: 12 fractures; group 2: 25) were classified as 9 A1, 21 A3, 3 B1, 3 B2, and 1 B3 OTA/AO types. Eighteen children (22 fractures) were included with average follow-up of 33.3 months (6-84). The average age was 12.8 years (4-16).

RESULTS

Main fracture pattern (75%) in group 1 was a posterior wall fracture (A1) caused by falls and sports in 50%. Six socket injuries had a hip dislocation, present only in group 1 (P < 0.001). The majority (84%) in group 2 had anterior wall/column (A3) fractures, caused by traffic accidents (88%). Fracture displacement in group 1 was higher than in group 2 (3.8 vs. 0.8 mm; P = 0.009). Group 2 had a lower Glasgow Coma Scale (P = 0.031) and a higher Injury Severity Score (P < 0.001). Nine (24%) fractures were treated operatively, significantly more were in group 1 (P < 0.001). Three (14%) children had complications including (LLD) (2) or hip dysplasia (2).

CONCLUSION

Compared with isolated pediatric acetabular fractures, fractures associated with pelvic ring injuries have less displacement and are less likely to require operative treatment, but they show more associated injuries. Because of potential hip joint growth disturbance, LLD and hip dysplasia can occur.

LEVEL OF EVIDENCE

Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Radiographic Evaluation of Acetabular Fractures: Review and Update on Methodology

Despite increased availability of modern imaging techniques, plain radiographs remain the initial step in the classification of acetabular fractures. The ability to interpret the injury configuration allows the surgeon to develop a thorough preoperative plan and to evaluate the quality of reduction and fixation intraoperatively. Proficiency in the mental conversion of a two-dimensional radiograph into a three-dimensional conceptual image is imperative. The widely used radiographic classification scheme developed by Judet and Letournel in the 1960s is both practical and simple. However, understanding the subtleties of the fracture pattern can be a challenge even for experienced surgeons. Current evaluation methods include CT and three-dimensional reconstructions in addition to plain radiographs. Our diagnostic algorithm uses three plain radiographs to classify the fracture into one of the 10 fracture patterns described by Judet and Letournel.

Instability of the Hip Joint After Posterior Acetabular Wall Fracture: Independent Risk Factors Remain Elusive

BACKGROUND

Exact determinants of hip instability have not been established for fractures of the posterior wall of the acetabulum involving ≤50% of the wall. Therefore, examination of the hip under anesthesia (EUA) is routinely performed. Recently, the superior exit point of the fracture has been reported to be an important identifiable risk factor. Pre-existing adult hip dysplasia (developmental dysplasia of the hip [DDH]) is thought to have a similar role. The purpose of this study was to determine if any known radiographic measurements and signs associated with DDH, or any fracture characteristics, are independent risk factors for hip instability after fracture of the posterior wall of the acetabulum.

METHODS

All patients with a posterior acetabular wall fracture (OTA 62.A1) treated at our institution between 2004 and 2015 were considered for the study. Inclusion criteria were an age of ≥18 years, an isolated posterior acetabular wall fracture involving ≤50% of the acetabular wall, adequate imaging, and documented EUA results. Evaluated variables included fracture fragment size, superior exit point of the fracture, center-edge angle, acetabular index, Tönnis angle, lateralized head sign, crossover sign, posterior wall sign, ischial spine sign, and hip version. Data were examined using univariate testing, followed by a multivariate logistic regression analysis.

RESULTS

Sixty-eight patients met all of the inclusion criteria. Univariate analyses identified the posterior wall sign (p = 0.033), ischial spine sign (p = 0.030), and proximity of the superior exit point of the fracture to the acetabular dome (p = 0.044) as having a significant association with hip instability. However, multivariate logistic regression modeling revealed that none of these factors were significant independent risk factors.

CONCLUSIONS

Consistent with previous studies, univariate analyses identified certain radiographic findings as significant risk factors for hip instability in the setting of a fracture of the posterior wall of the acetabulum. However, subsequent multivariate logistic regression modeling showed that no studied variable was an independent risk factor. Our results indicate that important factors leading to hip instability are yet to be identified or the contributions of the measured variables are relatively small. Therefore, EUA should remain the main clinical determinant of hip stability status.

LEVEL OF EVIDENCE

Prognostic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Treatment of Hip Dislocations and Associated Injuries: Current State of Care

Hip dislocations, most often caused by motor vehicle accidents or similar high-energy trauma, traverse a large subset of distinct injury patterns. Understanding these patterns and their associated injuries allows surgeons to provide optimal care for these patients both in the early and late postinjury periods. Nonoperative care requires surgeons to understand the indications. Surgical care requires the surgeon to understand the benefits and limitations of several surgical approaches. This article presents the current understanding of hip dislocation treatment, focusing on anatomy, injury classifications, nonoperative and operative management, and postinjury care.