Graf Type-IV Hips Have a Higher Risk of Residual Acetabular Dysplasia at 1 Year of Age Following Successful Pavlik Harness Treatment for Developmental Hip Dysplasia.

BACKGROUND: We asked whether patient-specific factors and ultrasound (US) measurements of hip dysplasia severity at initial examination influence short-term residual acetabular dysplasia in patients successfully treated with Pavlik harness for developmental hip dysplasia. METHODS: After IRB approval, 134 hips (84 patients) successfully treated by the Pavlik method between August 2011 and October 2014 with follow-up at 12 months of age were identified. Early successful treatment was defined as normal examination and US after approximately 12 weeks of Pavlik treatment. Multivariate linear and logistic regression models were used to identify factors associated with acetabular index (AI) measurements at 12 months as well as factors associated with an increase in AI between the 6- and 12-month timepoints (dysplastic progression). RESULTS: The study consisted of 134 hips (84 patients). The distribution of dysplastic, Barlow, and Ortolani hips was 44.8% (N=60), 30.6% (N=41), and 24.6% (N=33), respectively. The crude incidence of residual dysplasia at the 6-month visit (AI>30 degrees) was 11.7% (12/102). The incidence of residual dysplasia at the 12-month visit (AI>28 degrees) was 11.8% (13/111). Graf type was the only variable associated with AI values at the 12-month visit (mean difference: Graf type-IV-Other, 2.6; 95% confidence interval, 0.3-4.9; P=0.026). CONCLUSIONS: The risk of residual acetabular dysplasia after normal hip US following Pavlik treatment is not negligible. Radiographic surveillance is warranted to monitor and screen for dysplasia progression. Patients with dislocated Graf type-IV hips at diagnosis are at increased risk of residual acetabular dysplasia at 1 year after successful treatment with the Pavlik method. LEVEL OF EVIDENCE: Level III-therapeutic study.

Local Infiltration Analgesia Compared With Epidural and Intravenous PCA After Surgical Hip Dislocation for the Treatment of Femoroacetabular Impingement in Adolescents.

BACKGROUND: Open treatment of femoroacetabular impingement (FAI) through a surgical hip dislocation (SHD) approach has been reported to allow for improvement in pain and function. However, the approach require a trochanteric osteotomy and may be associated with high level of pain after surgery. Currently, there is no systematic approach for pain management after SHD for treatment of FAI. METHODS: A retrospective chart review was used to collect data from 121 subjects (12 to 21 y and below) who received periarticular local infiltration analgesia (LIA, n=20), epidural analgesia (n=72), or intravenous patient-controlled analgesia (PCA, n=29) after SHD from January 2003 to June 2014. Verbal pain scores, opioid consumption, incidence of side effects/complications, and length of hospital stay (LOS) were recorded. All nonopioid medications with analgesic potential were included in the statistical models as potential confounding variables RESULTS:: Twelve hours after surgery, the odds of moderate/severe pain were higher in the PCA group (odds ratio, 20.5; 95% confidence interval (CI), 1.7-243.8; P=0.0166] and epidural group (odds ratio, 5.2; 95% CI, 0.7-92.0; P=0.3218) compared with the LIA group. There was no difference in pain scores across all groups 1 hour (P=0.0675) or 24 hours (P=0.3473) postoperatively. Total opioid consumption in the LIA group was 59.8% (95% CI, 15.0%-81.0%; P=0.0175) lower than the total opioid consumption in the epidural group and 60.7% (95% CI, 17.3-81.3; P=0.0144) lower than the total opioid consumption in the PCA group. LOS was increased in the epidural (mean difference, 22.1; 95% CI, 6.8-37.4 h; P=0.0051) and PCA (mean difference, 16 h; 95% CI, 1-31.5 h; P=0.0367) groups relative to the LIA group. There was 0 (0%) complication in the LIA group compared with 11 (15.3%) in the epidural group. CONCLUSIONS: LIA was more effective at controlling pain 12 hours after surgery in comparison with PCA with similar pain control to epidural. LIA was associated with significantly lower need for opioids and shorter LOS compared with the PCA and epidural protocols. Periarticular infiltration should be considered for pain management after SHD for treatment of FAI in adolescents. LEVEL OF EVIDENCE: Level III-retrospective comparative study.

Measurement of Femoral Version by MRI is as Reliable and Reproducible as CT in Children and Adolescents With Hip Disorders.

BACKGROUND: Femoral version measurement techniques based on magnetic resonance imaging (MRI) studies have been developed as an alternative to the high levels of ionizing radiation associated with computed tomography (CT)-based methods. Previous studies have not evaluated the reliability, repeatability, and accuracy of MRI-based femoral version measurements in an adolescent population. METHODS: Subjects who underwent MRI and CT studies for clinical suspicion of hip pain secondary to hip dysplasia or femoroacetabular impingement between 2011 and 2013 were identified. Rapid sequence femoral version images were obtained from MRI Hip dGEMRIC and/or postarthrogram studies. Femoral version images were also obtained from bilateral CT lower extremity, without contrast, studies. Measurements were made by 1 fellowship-trained, pediatric hip preservation attending surgeon, 2 pediatric orthopaedic surgical fellows, and 1 fellowship-trained musculoskeletal radiologist on 2 separate occasions. Linear mixed models were used to estimate the reliability and repeatability associated with CT-based and MRI-based measurements (intraclass correlation coefficients) and to estimate the agreement (CT-MRI) between the 2 techniques. RESULTS: The mean age of 36 subjects was 15.4 years (±4.1 y). Interrater reliability was 0.91 (95% CI, 0.86-0.95) for the CT technique compared with 0.90 (95% CI, 0.86-0.94) for the rapid sequence MRI technique. Intrarater reliability for the CT technique was 0.96 (95% CI, 0.91-0.98) compared with 0.95 (95% CI, 0.90-0.97) for the MRI technique. The agreement between the MRI-based and CT-based techniques (bias: 1.9 degrees, limits of agreement: -11.3 to 14.9 degrees) was similar to the agreement between consecutive MRI measurements (bias: 0.4 degrees, limits of agreement: -7.8 to 8.6 degrees) as well as consecutive CT measurements (bias: 0.5 degrees, limits of agreement: -8.8 to 9.9 degrees). CONCLUSIONS: The interrater and intrarater reliability and repeatability estimates (intraclass correlation coefficient values) associated with both techniques was excellent (>0.90). Acquirement of axial images at the pelvis and knee during MRI for investigation of adolescents with hip pain allows for reliable measurement of femoral version. LEVEL OF EVIDENCE: Level II-diagnostic study.

Multimodal nerve monitoring during periacetabular osteotomy identifies surgical steps associated with risk of injury.

PURPOSE: Sciatic nerve palsy after periacetabular osteotomy (PAO) is a serious complication. The purpose of this study was to determine whether a multimodal sciatic monitoring technique allows for identification of surgical steps that place the sciatic nerve at risk. METHODS: Transcranial electrical motor evoked potentials (TcMEPs), somatosensory evoked potentials (SSEPs), and spontaneous electromyography (EMG) were monitored in a consecutive series of 34 patients (40 hips) who underwent PAO for the treatment of symptomatic hip dysplasia between January 2012 and November 2014. There were 29 females (85%) and five males (15%) with an average age of 19 years (range, 12-36 years) at the time of surgery. RESULTS: We detected eight temporary sciatic nerve monitoring alerts in six patients (incidence of 15%). The events included decrease in amplitude of the TcMEPs related to the position of the hip during incomplete ischium osteotomy and placement of a retractor in the sciatic notch during the posterior column osteotomy (N = 3), generalized bilateral decrease in TcMEPs during fragment manipulation and fixation in association with acute blood loss (N = 2), and a change in SSEPs during a superior pubic osteotomy and supra-acetabular osteotomy (N = 1). At the end of the procedure, TcMEPs and SSEPs were at baseline and there was no abnormal pattern on EMG in all patients. Post-operatively, at two, six, 12 weeks, and six and 12 months, no motor weakness or sensory deficits were noted. CONCLUSION: Multimodal neuromonitoring allowed for identification of intra-operative steps and maneuvers that potentially place the sciatic nerve at higher risk of injury.

Does Surgeon Experience Impact the Risk of Complications After Bernese Periacetabular Osteotomy?

BACKGROUND: Bernese periacetabular osteotomy (PAO) is a technically challenging procedure with potential risk for major complications and a previously reported steep learning curve. However, the impact of contemporary hip preservation fellowships on the learning curve of PAO has not been established. QUESTIONS/PURPOSES: (1) What was the frequency of major complications during the PAO learning curve of two surgeons who recently graduated from hip preservation fellowships? (2) Is increasing level of experience associated with the risk of a complication and with operative time, a possible surrogate measure of surgical performance? METHODS: We retrospectively studied 81 PAOs performed by one of two surgeons who recently graduated from a hip preservation fellowship during their first 4 years of practice in two institutions. One of the surgeons participated as a fellow in 78 PAOs with an increasing level of responsibility during the course of 1 full year. The other surgeon performed 41 PAOs as a fellow during 6 months, also with an increasing level of responsibility during that time. There were 68 (84%) female and 13 (16%) male patients (mean age, 18 years; range, 10-36 years). The frequency of complications was recorded early and at 1 year after surgery and graded according to a validated classification system describing five grades of complications. Complications that required surgical intervention (Grade III) and life-threatening complications (Grade IV) were considered major complications. Persistent pain after surgery, although considered a failure of PAO, was not considered a surgical complication as a result of the multifactorial etiology of pain after hip-preserving surgery. However, early reoperation and revision surgery were counted as complications. To evaluate the association between increasing level of experience and the occurrence of complications, we divided each surgeon's experience into his first 20 procedures (initial interval) and his second 20 (experienced interval) to test whether the incidence of complications or operative time was different between the two intervals. Because the association between experience and the likelihood of a complication was estimated to be consistent between the two surgeons, the analysis was performed with data pooled from the two surgeons. To test whether there was a difference in the likelihood of a complication in the initial and the experienced intervals, a multivariate logistic regression analysis was performed and the adjusted risk of a complication between the two intervals was calculated. Linear regression analyses were used to test the association between surgeon level of experience and operative time. RESULTS: The overall incidence of major (Grade III or Grade IV) complications was 6% (95% confidence interval [CI], 2%-14%). These included deep infection (3% [three of 81]), intraoperative posterior column fracture (1% [one of 81]), and pulmonary embolism (1% [one of 81]). With the numbers available, the risk of a complication did not decrease with increasing surgeon experience. After controlling for body mass index and surgeon, the frequency of a complication did not decrease in the experienced interval relative to the initial interval (odds ratio, 0.78; 95% CI, 0.25-2.4; p = 0.6623). The adjusted risk difference between the experienced interval relative and the initial interval was 6% (95% CI, -11% to 23%). When experience was modeled as a continuous variable (number of PAOs performed), increasing experience was not associated with a lower likelihood of a complication (odds ratio per one PAO increase in experience, 0.99; 95% CI, 0.94-1.04; p = 0.5478). However, after adjusting for body mass index and surgeon, increased experience was associated with a reduction in operative time (slope [change in log operative time per one procedure increase in experience], -0.005; 95% CI, -0.009 to -0.0005; p = 0.0292). For every one additional PAO increase in experience, there was a 0.45% decrease in operative time (95% CI, 0.05%-0.86% decrease]. CONCLUSIONS: With a case exposure greater than 40 PAOs and progressive surgical responsibility during contemporary structured training, two young surgeons were able to perform PAO with a low risk of complications. However, even with that surgical experience before independent practice, surgical time decreased over the first 40 PAOs they performed independently. Our data may help guide orthopaedic residency and hip preservation fellowship programs in establishing training requirements and assessing competency in PAO. LEVEL OF EVIDENCE: Level III, therapeutic study.

Return to Play Following Open Treatment of Femoroacetabular Impingement in Adolescent Athletes.

INTRODUCTION: After treatment of femoroacetabular impingement (FAI) in adolescent competitive athletes, the rate, timing, and level of return to play have not been well reported. METHODS: Adolescent athletes who underwent open FAI treatment were assessed at a minimum 1-year follow-up. Patients completed a self-reported questionnaire centered on the time and level of return to play. Pain and functional outcomes were assessed using the modified Harris Hip Score (mHHS) and the Hip Disability and Osteoarthritis Outcome Score (HOOS). RESULTS: Among the 24 athletes included, 21 (87.5%) (95% confidence interval [CI], 67.6% to 97.3%) successfully returned to play after open FAI treatment. The median time to return to play was 7 months (95% CI, 6 to 10 months). Of the 21 who returned to play, 19 (90%) returned at a level that was equivalent to or greater than their level of play before surgery. Three athletes (12.5%) did not return to play and indicated that failure to return to play was unrelated to their hip. There was significant improvement in the mHHS (P < 0.0001), HOOS (P < 0.0001), α angle (P < 0.0001), and offset (P < 0.0001). DISCUSSION: Most adolescent athletes can expect to return to the same or better level of sports participation during the first year after open treatment of FAI.

Factors That Predict Blood Loss After Bernese Periacetabular Osteotomy.

Although strategies to reduce bleeding and avoid allogeneic transfusion have been described, there is controversy about the factors associated with blood loss after Bernese periacetabular osteotomy. This study was conducted to determine risk factors for postoperative blood loss. After institutional review board approval was obtained, a retrospective review was conducted of 41 young patients who underwent periacetabular osteotomy for symptomatic acetabular dysplasia over a 3-year period. Of these patients, two-thirds donated blood before surgery. A Cell Saver Elite autotransfusion system (Haemonetics, Braintree, Massachusetts) was used intraoperatively in all cases. Hemoglobin and hematocrit were obtained before surgery and during the hospital stay. The primary outcome variable was the percentage of total blood volume lost during surgery. Univariate analysis was performed to test the association between potential predictors of blood volume loss. Candidate variables that were significant at alpha=0.15 were tested with multivariate analysis. The average percentage of blood volume lost during surgery was 30.3% (95% confidence interval, 25.1%-35.5%). Univariate analysis showed that operative time, arthrotomy, femoral head-neck osteochondroplasty, labral procedure, male sex, and age were prognostic factors associated with increased blood volume loss. However, operative time (average, 294.6 minutes; range, 204-444 minutes) was the only independent predictor of increased blood loss in the final model. Additional procedures, such as femoral head-neck osteochondroplasty and labral repair or debridement performed through an anterior hip arthrotomy at the time of periacetabular osteotomy, were associated with increased operative time. The findings suggest that all patients undergoing periacetabular osteotomy, including those having concomitant procedures, may benefit from pre- and intraoperative strategies to conserve blood and avoid allogeneic transfusion. [Orthopedics. 2016; 39(6):e1147-e1153.].

Femoroacetabular Impingement Is Associated With Sports-Related Posterior Hip Instability in Adolescents: A Matched-Cohort Study.

BACKGROUND: Femoroacetabular impingement (FAI) deformity has been associated with posterior hip instability in adult athletes. PURPOSE: To determine if FAI deformity is associated with posterior hip instability in adolescents, the femoral head-neck junction or acetabular structure in a cohort of adolescent patients who sustained a low-energy, sports-related posterior hip dislocation was compared with that in a group of healthy age- and sex-matched controls with no history of hip injury or pain. STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: We identified 12 male patients (mean age, 13.9 years; range, 12-16 years) who sustained a sports-related posterior hip dislocation and underwent a computed tomography (CT) scan after closed reduction. For each patient, 3 age- and sex-matched healthy controls were identified. Femoral head-neck type was assessed by measurement of the alpha angle on the radially oriented CT images at the 12-, 1-, 2-, and 3-o'clock positions. Age, body mass index (BMI), alpha angle at each position, acetabular version, Tönnis angle, and lateral center-edge angle (LCEA) on the involved hip in the dislocation group were compared with those of the matched controls using a mixed-effects model. A logistic regression analysis using a generalized estimating equation was used to compare the percentage of subjects with cam-type FAI deformity (alpha angle >55°) in each group. RESULTS: The dislocation and control groups were similar in age distribution and BMI (P > .05). The mean alpha angles were statistically significantly higher in the dislocation group compared with the control group at the superior (46.3° ± 1.1° vs 42.7° ± 0.6°; P = .0213), superior-anterior (55.5° ± 1.9° vs 46.0° ± 1.3°; P = .0005), and anterior-superior (54.9° ± 1.5° vs 48.9° ± 1.0°; P = .0045) regions. Cam deformity was present in a larger proportion of patients in the dislocation group than in the control group (P < .0035). An alpha angle greater than 55° was present in 16.7% of the dislocation group and 0% of the control group at the 12-o'clock position (P = .1213), 41.7% versus 0% at the 1-o'clock position (P = .0034), 58% versus 6% at the 2-o'clock position (P = .0004), and 25% versus 2.8% at the 3-o'clock position (P = .0929). Acetabular anteversion was lower in the dislocation group (9.6° ± 1.4°) compared with the control group (15.1° ± 0.8°) (P = .0068). Mean acetabular LCEA was within a normal range in both groups. CONCLUSION: A significantly higher mean alpha angle from the superior to the anterior-superior regions of the femoral head-neck junction and lower acetabular version were found in adolescents who sustained low-energy, sports-related posterior hip dislocations.

Is Assessment of Femoral Head Perfusion During Modified Dunn for Unstable Slipped Capital Femoral Epiphysis an Accurate Indicator of Osteonecrosis?

BACKGROUND: The modified Dunn procedure, which is an open subcapital realignment through a surgical dislocation approach, has gained popularity for the treatment of unstable slipped capital femoral epiphysis (SCFE). Intraoperative monitoring of the femoral head perfusion has been recommended as a method of predicting osteonecrosis; however, the accuracy of this assessment has not been well documented. QUESTIONS/PURPOSES: We asked (1) whether intraoperative assessment of femoral head perfusion would help identify hips at risk of developing osteonecrosis; (2) whether one of the four methods of assessment of femoral head perfusion is more accurate (highest area under the curve) at identifying hips at risk of osteonecrosis; and (3) whether specific clinical features would be associated with osteonecrosis occurrence after a modified Dunn procedure for unstable SCFE. METHODS: Between 2007 and 2014, we performed 29 modified Dunn procedures for unstable SCFE (16 boys, 11 girls; median age, 13 years; range, 8-17 years); two were lost to followup before 1 year. During this period, six patients with unstable SCFE were treated by other procedures. All patients undergoing modified Dunn underwent assessment of epiphyseal perfusion by the presence of active bleeding and/or by intracranial pressure (ICP) monitoring. In the initial five patients perfusion was recorded once, either before dissection of the retinacular flap or after fixation by one of the two methods. In the remaining 22 patients (81%), perfusion was systematically assessed before dissection of the retinacular flap and after fixation by both methods. Minimum followup was 1 year (median, 2.5 years; range, 1-8 years) because osteonecrosis typically develops within the first year after surgery. Patients were assessed for osteonecrosis by the presence of femoral head collapse at radiographs obtained every 3 months during the first year after surgery. Seven (26%) of the 27 patients developed osteonecrosis. Measures of diagnostic accuracy including sensitivity, specificity, and the area under the receiver operating curve (AUC) were estimated. Multiple variable logistic regression analyses were used to test whether the test options were better than random chance (AUC > 0.50) at differentiating between patients who did versus did not develop osteonecrosis. Nonparametric methods were used to test for a difference in AUC across the four methods. A secondary analysis was performed to identify risk factors associated with osteonecrosis. RESULTS: After adjusting for body mass index, which was found to be a confounding variable, assessment of femoral head perfusion with ICP monitoring before retinaculum dissection (adjusted AUC: 0.79; 95% confidence interval [CI], 0.58-0.99; p = 0.006), femoral head perfusion with ICP monitoring after definitive fixation (adjusted AUC: 0.82; 95% CI, 0.65-1.0; p < 0.001), bleeding before retinaculum dissection (adjusted AUC: 0.77; 95% CI, 0.58-0.96; p = 0.006), and bleeding after definitive fixation (adjusted AUC: 0.81; 95% CI, 0.63-0.99; p = 0.001) were found to be helpful at identifying osteonecrosis. We were not able to identify a specific test that had performed best because there was no difference (p = 0.8226) in AUC across the four methods. With the numbers available, we were unable to identify clinical factors predictive of osteonecrosis in our cohort. CONCLUSIONS: Assessments of femoral head blood perfusion by ICP monitoring or by the presence of active bleeding in combination with the patient's body mass index are effective at differentiating between patients who do versus do not develop osteonecrosis after a modified Dunn procedure for unstable SCFE. Additional research is needed to determine whether information gained from assessment of femoral head perfusion during surgery should be used to guide targeted treatment recommendations that may reduce the development of femoral head deformity secondary to osteonecrosis. LEVEL OF EVIDENCE: Level III, diagnostic study.

Higher Pavlik Harness Treatment Failure Is Seen in Graf Type IV Ortolani-positive Hips in Males.

BACKGROUND: Patients with developmental dysplasia of the hip (DDH) whose hips are dislocated but reducible (Ortolani positive) are more likely to experience Pavlik harness treatment failure than are patients with dysplastic and reduced but dislocatable (Barlow positive) hips. However, data regarding factors associated with failure are limited and conflicting. QUESTIONS/PURPOSES: We asked: (1) What is the frequency of Pavlik harness treatment failure among Ortolani-positive hips, Barlow-positive hips, and dysplastic hips? (2) What are the factors predictive of failure of Pavlik harness treatment for Ortolani-positive hips? METHODS: In this retrospective study we identified 150 patients who underwent the Pavlik harness method for treatment of DDH between August 2011 and July 2015. Six patients initially treated at an outside facility, four patients with associated conditions, and three who pursued treatment elsewhere were excluded. A total of 137 patients (215 hips) with a median age at the time of Pavlik placement of 30 days (range, 4-155 days) were included. Of the 215 hips, 78 (36.3%) were Ortolani positive, 60 (27.9%) were Barlow positive, and 77 (35.8%) were stable, with the diagnosis of dysplasia made on ultrasound. All patients were treated with the Pavlik harness method. The primary outcome was failure of the Pavlik harness to achieve and maintain concentric hip reduction assessed by examination and ultrasound. All patients were followed after completion of Pavlik treatment for a minimum of 2 months (mean, 3 months; range, 2-4 months). In addition, 90% (122 of 137) of the patients were followed for a minimum of 6 months. Patient-specific data including family history, breech versus cephalic presentation at birth, age, sex, laterality, and hip abduction were recorded. Ultrasound data at the time of diagnosis included Graf classification, alpha angle, and percentage of femoral head coverage. RESULTS: The Pavlik harness method failed in 27% (21 of 78) of hips that were Ortolani positive, 8% (six of 77) with dysplasia, and 5% (three of 60) that were Barlow positive. After controlling for potential confounding variables, such as range of hip abduction, male sex (adjusted odds ratio [OR], 6.9; 95% CI, 2.0-24.2; p = 0.002) and Graf Type IV ultrasound classification (dislocated hip with alpha angle less than 43° and labrum displaced downward) (OR, 4.4; 95% CI, 1.3-15.4; p = 0.019) were identified as independent predictors of failure of Pavlik treatment among Ortolani-positive hips. CONCLUSIONS: Ultrasound imaging of the hip should be part of the initial assessment for Ortolani-positive hips, as the ultrasound classification was found to have prognostic implications. Parents of male infants with Graf Type IV hips should be counseled regarding the higher risk of Pavlik failure. Future well-designed prospective controlled studies are necessary to establish whether alternative strategies to the Pavlik harness might improve the early outcomes of DDH in males with Graf Type IV hips. LEVEL OF EVIDENCE: Level III, therapeutic study.

MRI as a reliable and accurate method for assessment of posterior hip dislocation in children and adolescents without the risk of radiation exposure.

BACKGROUND: Posterior hip dislocation in children and adolescents may involve the non-ossified posterior acetabular wall. Plain radiographs and computed tomography (CT) have been shown to underestimate injury to the unossified acetabulum as well as associated soft-tissue structures. OBJECTIVE: The purpose of this study was to describe findings on radiographs, CT and magnetic resonance imaging (MRI) after posterior hip dislocation in a series of adolescents and to report the intraoperative findings, which are considered the gold standard. Measurements of the posterior wall length using MRI and CT scans were also performed. MATERIAL AND METHODS: After institutional review board approval, 40 patients who sustained a traumatic posterior dislocation of the hip between September 2007 and April 2014 were identified. Inclusion criteria were (1) age younger than 16 years old and (2) availability of MRI obtained following closed reduction of the hip. Eight male patients and one female patient with an average age of 13.2 years (range: 10.1-16.2 years) underwent hip MRI following posterior dislocation. Seven of the nine patients also underwent evaluation by CT. Plain radiographs, CT scans and MRI were evaluated in all patients by a single pediatric radiologist blinded to surgical findings for joint space asymmetry, posterior wall fracture, femoral head fracture, labrum tear, complete or partial ligamentum teres rupture and presence of intra-articular fragments. Six patients underwent surgical treatment and the intraoperative findings were compared with the imaging findings. RESULTS: CT identified all bone injuries but underestimated the involvement of posterior wall fractures. Assessment of the posterior wall size and fracture displacement was possible with MRI. All surgically confirmed soft-tissue injuries, including avulsion of the posterior labrum, were identified preoperatively on MRI. The measurement of posterior wall length was not statistically different using CT and MRI. CONCLUSION: Intraoperative pathological findings at the time of open surgical treatment were universally recognized on MRI but not on CT scans. MRI should be considered for evaluation of the hip following closed reduction for the treatment of a posterior dislocation in children and adolescents as it reliably allows assessment of intra-articular pathology without the risk of radiation exposure.