A radiographic study of the ossification of the posterior wall of the acetabulum: implications for the diagnosis of pediatric and adolescent hip disorders

Traumatic Hip Dislocation: Pediatric and Adult Evaluation and Management

Traumatic hip dislocation of a native hip joint represents an orthopaedic emergency that should be treated promptly. Dislocations can be classified based on the associated injuries and the direction of dislocation. Expeditious evaluation, reduction, and management of associated injuries are required to optimize short and long-term function of the hip. There are several important differences between the blood supply and ossification of the pediatric hip that necessitate different strategies for the evaluation and management of traumatic hip dislocations in pediatric patients. Appropriate treatment is dictated by the direction and type of dislocation as well as associated injuries. In addition to closed reduction, arthroscopy, open reduction (potentially with fracture fixation and/or soft-tissue repair), osteotomy, and total hip arthroplasty all have roles in treatment. Consensus on optimal postreduction activity protocols after simple hip dislocation remain unestablished. Short and long-term outcomes are largely driven by the amount of time from injury to reduction and associated injuries.

Increased combined anteversion is associated with larger posterior acetabular rim ossification in patients with femoroacetabular impingement syndrome

PURPOSE

(1) To determine the prevalence, magnitude and distribution pattern of acetabular rim ossification in patients with femoroacetabular impingement syndrome (FAIS) and (2) to determine the association between acetabular rim ossification and rotational abnormalities of the hip.

METHODS

Patients underwent hip arthroscopic surgery for FAIS at our institute between January 2021 and May 2022 were retrospectively reviewed. Patients were included if preoperative computed tomography (CT) images of the operated hip and ipsilateral distal femur were available for the measurement of femoral and acetabular anteversion. The presence and size of acetabular rim ossification were evaluated on coronal CT sections for the superior half of the acetabulum on each clockface location. The associations between acetabular rim ossification and radiographic parameters of hip rotational morphology were examined.

RESULTS

A total of 214 hips were included. Acetabular rim ossification was found in 167 hips (78%) and the most common locations were 10 and 11 o'clock. Patients presenting with acetabular rim ossification had a mean size of 4.6 ± 1.6 mm. It was the largest at 9 o'clock position (4.9 ± 2.2 mm), with a decreasing trend in size from posterior to anterior. Logistics regression analysis found age was associated with the occurrence of posterior ossification (p = 0.002). Linear regression analysis found age (p = 0.049) and male sex (p < 0.001) were significantly correlated with the size of ossification. Patients with increased cranial combined anteversion had larger posterior ossification than patients with normal and decreased cranial combined anteversion (4.2 ± 2.9 vs. 3.1 ± 2.5 mm, p = 0.016; 4.2 ± 2.9 vs. 2.5 ± 2.4 mm, p = 0.005).

CONCLUSION

Increased combined anteversion is associated with greater posterior acetabular rim ossification. The presence and size of acetabular rim ossification are positively associated with older age and male sex.

LEVEL OF EVIDENCE

Level III.

Magnetic Resonance Imaging in Pediatric Acetabulum Fractures with Open Triradiate Cartilage-A Report of 3 Cases

We present three cases of posterior wall acetabulum fractures occurring in pediatric patients with open triradiate cartilage for whom preoperative magnetic resonance imaging was obtained and open reduction and internal fixation was done. All patients had excellent outcomes at an average of 68-week follow-up. Failure to adequately recognize the severity of pediatric acetabulum fractures can lead to detrimental long-term sequelae in acetabular development when treated nonsurgically. Management of this rare injury is not well reported in the literature. We highlight the utility of MRI in evaluating potential nonosseous injury and examining the articular surface to guide surgical management.

Traumatic hip dislocations in a pediatric cohort: The importance of advanced imaging

Purpose

Given that pediatric traumatic hip dislocations are relatively rare, the purpose of the current study is twofold: first, to contribute a significant cohort to the existing corpus, and second, to provide evidence toward the role that computed tomography and magnetic resonance imaging could play in identification and management of this type of injury.

Methods

A retrospective review was conducted of all patients with traumatic hip dislocation who presented from 2012 to 2022 at a tertiary-level pediatric trauma center. Data regarding demographics, mechanism of injury, imaging, and treatment were tabulated. Outcomes of interest included immobilization length, concomitant injuries, imaging performed and findings, and rates of avascular necrosis, pain, and stiffness. Concomitant injuries were identified using imaging, clinical, and operative notes. Differences between categorical variables were compared using chi-square analysis or Fischer-exact testing, while continuous variables were compared using Student t tests or Wilcoxon rank sum tests when appropriate.

Results

Thirty-four patients were identified. Postreduction, 28 patients had a cumulative 17 magnetic resonance imaging, 19 computed tomographies, and 1 intraoperative arthrogram. Of these, 16 patients had 19 injuries identified on advanced imaging that were missed on initial radiographs. Eleven of these patients went on to operative treatment. In eight of these, postreduction advanced imaging helped guide the decision for surgery. In four patients, magnetic resonance imaging was necessary to fully characterize injury to the posterior acetabular rim after initial identification on computed tomography. Magnetic resonance imaging was also used to rule out one computed tomography-diagnosed acetabular fracture.

Conclusion

Magnetic resonance imaging is valuable to fully define associated rim and intra-articular injuries following initial treatment of pediatric traumatic hip dislocations.

Level of evidence

Level IV diagnostic study.

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.

Acetabular Labral Tear with a Missed Posterior Wall Fracture in an Adolescent Athlete: A Case Report

CASE

We present an adolescent contact-sport athlete presenting with hip pain after a traumatic in-play event. After delayed clinical improvement, a magnetic resonance arthrogram (MRA) revealed a posterior acetabular labral tear and the patient was referred for arthroscopic repair. However, subsequent critical interpretation of the MRA demonstrated a missed concomitant posterior acetabular wall fracture, which was later confirmed with computed tomography.

CONCLUSION

Despite the low incidence of acetabular fractures in adolescents, this case report highlights the importance of maintaining clinical suspicion in young athletes after a traumatic injury, recognizing the association with labral tears, and acknowledging the limitations of certain imaging modalities.

Normal Humeral Head Ossification in Pediatric and Adolescent Shoulders Can Mimic Hill-Sachs Lesions: A Magnetic Resonance Imaging-based Study

BACKGROUND

The sequential maturation of the humeral head (HH) as viewed on magnetic resonance imaging (MRI) has not been described to date. Proper assessment may be complicated by the presence of physeal tissue in pediatric patients. Past studies suggest that skeletally immature patients may also have a higher risk of a false-positive diagnosis of Hill-Sachs lesion on MRI. The purpose of this study was to define pediatric HH developmental patterns using MRI and to investigate for any associations with findings of known false-positive Hill-Sachs.

METHODS

Picture Archiving and Communication System (PACS) records at an urban academic tertiary care musculoskeletal facility from 2014 to 2020 were queried for shoulder MRI in patients aged 0 to 15 years. Patients were excluded if they had a history of glenohumeral instability, fracture, growth arrest, brachial plexus injury, surgery, or infection. All images were independently evaluated by a musculoskeletal fellowship-trained radiologist. Each HH was staged based on skeletal maturity.

RESULTS

For both sexes, HHs matured in a predictable manner with increasing chronological age associated with a higher ossification stage. False Hill-Sachs lesions were observed in girls aged 4 to 7 and boys aged 5 to 14, exclusively during stage I to II ossification.

CONCLUSIONS

False Hill-Sachs lesions were visualized on MRI in stage I to II proximal humerus ossification. Due to differential timing of skeletal maturation, males present with false Hill-Sachs lesions at a later age than females on average. When interpreting shoulder MRI for glenohumeral instability, clinicians should be cautious of false Hill-Sachs lesions, especially in younger patients with distinct greater tuberosity and HH ossification centers (stage I to II ossification).

LEVEL OF EVIDENCE

Level III.

Retroversion of the hemipelvis rather than hypoplastic posterior wall decreases acetabular anteversion in hips affected by Perthes disease

The acetabular retroversion has a moderate incidence of 31-60% in all patients of the Perthes disease. It might be caused by posterior wall dysplasia based on recent animal researches. However, some studies support that hemipelvic retroversion is the main factor for the acetabular retroversion. The primary pathological factor of increasing retroversion angle is still controversial anatomically. This study aimed to identify whether there is acetabular retroversion in children with Perthes disease,and to find a method to distinguish version types. Forty children with unilateral Perthes disease who were admitted to our hospital from January 1, 2012 to December 31, 2018 were enrolled, and 40 controls were matched based on sex and age. The acetabular anteversion angle (AAA), internal wall anteversion angle (IWAA), anterior wall height of the acetabulum (A), acetabular posterior wall height (P), and acetabular width (W) were assessed on computed tomography (CT) at the level of the femoral head center. The acetabular wall difference index (AWDI; AWDI = P-A)/W*100) was calculated. The mean AAA was significantly lower in Perthes disease hips (10.59 (8.05-12.46)) than in contralateral hips (12.04 (9.02-13.33)) (p = 0.002) but did not differ from control hips (9.68 ± 3.76) (p = 0.465). The mean IWAA was significantly lower in Perthes hips (9.16 ± 3.89) than in contralateral hips (11.31 ± 4.04) (p = 0.000) but did not differ from control hips (9.43 ± 3.82) (p = 0.753). The mean AWDI did not differ between Perthes hips (0.41 ± 4.94) and contralateral hips (- 1.12 (- 4.50, 2.17)) (p = 0.06) or control hips (- 0.49 ± 5.46) (p = 0.437). The mean W was significantly higher in Perthes hips (44.61 ± 5.06) than in contralateral hips (43.36 ± 4.38) (p = 0.000) but did not differ from control hips (45.02 ± 5.01) (p = 0.719). The mean A and P did not differ between Perthes hips and contralateral hips or control hips. Correlation analysis of all hip joints revealed a significant correlation between AAAs and IWAAs (r = 0.772; r = 0.643; r = 0.608; and r = 0.540). Linear regression analysis revealed that AAAs increased with IWAAs. Multiple linear regression showed that IWAAs and AWDIs have good predictive value for AAAs in both Perthes and control hips (R² = 0.842, R² = 0.869). In patients with unilateral Perthes disease, the affected acetabulum is more retroverted than that on the contralateral side, which may be caused by hemipelvic retroversion. The measurements in this study could distinguish the form of acetabular retroversion. IWAAs and AWDIs can be used as new observations in future studies of acetabular version.

Acetabular Coverage Decreases at the End of Skeletal Growth: A 3DCT Study of Healthy Hips

BACKGROUND

Abnormalities in size and position of the acetabulum have been linked to both developmental dysplasia of the hip and femoroacetabular impingement. Owing to its 3-dimensional (3D) complexity, plain radiography and cross-sectional studies [computed tomography (CT) and magnetic resonance imaging] have limitations in their ability to capture the complexity of the acetabular 3D anatomy. The goal of the study was to use 3D computed tomography reconstructions to identify the acetabular lunate cartilage and measure its size at varying ages of development and between sexes.

METHODS

Patients aged 10 to 18 years with asymptomatic hips and a CT pelvis for appendicitis were reviewed. Patients were stratified by sex and age: preadolescent (10 to 12), young adolescent (13 to 15), and old adolescent (16 to 18) in equal proportions. Materialise 3-matic was used to generate a 3D pelvic model, and the acetabular lunate cartilage surface area was calculated. The lunate cartilage was divided into anatomic segments: superior (11:00 to 1:00), anterior (1:00 to 4:00), and posterior (8:00 to 11:00). The femoral head surface area was calculated to control for patient size. Mixed effects models were generated predicting segment size where side was treated as a repeated measure. Absolute and relative (lunate cartilage to femoral head) models were generated.

RESULTS

Sixty-two patients (124 hips) were included. Females showed a significant decrease in femoral head coverage as age increased overall and in the 3 subsegments. The majority of changes occurred between the preadolescent and young adolescent groups. Males did not show an overall change, but the superior and anterior anatomic subgroups showed a significant decrease in coverage between the young and old adolescent groups. Male lunate cartilages were absolutely, but not relatively, larger than females. No clinically significant side-to-side differences were noted.

CONCLUSIONS

The relative femoral head coverage by the acetabular lunate cartilage reduced with increasing age, suggesting the growth of the femoral head outpaces the acetabular lunate cartilage's growth. This was more prominent in females. This study has important implications for expected acetabular coverage changes in the latter aspects of pediatric and adolescent development.

LEVEL OF EVIDENCE

Level III-diagnostic study.

Secondary Surgery and Residual Dysplasia Following Late Closed or Open Reduction of Developmental Dysplasia of the Hip

BACKGROUND

Outcomes studies following successful closed reduction of late-detected developmental dysplasia of the hip (DDH) reveal high rates of secondary reconstructive surgery with limited comparative data demonstrating lower rates of residual dysplasia with open reduction. The purpose of this study was to compare long-term outcomes, with regard to radiographic evidence of residual dysplasia and secondary reconstructive procedures, between late closed and late open reduction for DDH in patients 6 to 24 months of age at reduction.

METHODS

We identified all patients between 6 and 24 months of age who underwent closed or open reduction for DDH between 1980 and 2008 and were followed until at least 10 years of age. Outcomes included radiographic measurement of acetabular dysplasia after triradiate cartilage closure, development of osteonecrosis, and the need for secondary procedures for residual dysplasia.

RESULTS

One hundred and four hips underwent index closed reduction and 54 hips underwent index open reduction. There was no significant difference in the age at reduction (p = 0.07). Among the 116 hips for which initial anteroposterior pelvic radiographs were available, most closed reductions (55%) were performed in International Hip Dysplasia Institute (IHDI) grade-III hips whereas most open reductions (71%) were performed in IHDI grade-IV hips. Analysis of the hips that did not undergo a secondary procedure showed that those with an index open reduction had a greater lateral center-edge angle (mean and standard deviation, 27.2° ± 10.0° versus 22.4° ± 6.8° in the closed reduction cohort; p = 0.02), lower femoral head extrusion index (22.2% ± 8.9% versus 26.0% ± 6.2%; p = 0.04), and lower Sharp angle (43.3° ± 6.0° versus 46.6° ± 3.1°; p = 0.002) at triradiate closure. There was no difference in the prevalence of osteonecrosis (Bucholz-Ogden grades II, III, and IV) between the closed and open reduction cohorts (22% versus 19%, respectively; p = 0.60). Secondary procedures were performed more frequently after closed reduction than after open reduction (47% versus 30%, respectively; p = 0.03).

CONCLUSIONS

In patients with late reduction of DDH, closed reduction was associated with increased residual dysplasia and it was associated with a higher rate of secondary surgery in those >12 months old despite a decreased severity of displacement based on the IHDI classification. Additional, prospective studies with assessment of functional outcomes are needed to validate these findings.

LEVEL OF EVIDENCE

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

Contralateral slip after unilateral slipped capital femoral epiphysis is associated with acetabular retroversion but not increased acetabular depth and overcoverage

Overcoverage of the femoral head by the acetabulum, increased acetabular depth and retroversion have been associated with the etiology of slipped capital femoral epiphysis (SCFE). However, limited evidence exists about the impact of the acetabular morphology on the development of a contralateral slip following an initial presentation of unilateral SCFE. We aimed to investigate whether acetabular overcoverage as assessed by an increased lateral center-edge angle (LCEA) and low Tönnis angle, increased acetabular depth assessed by the acetabular depth-width ratio (ADR) and the presence of coxa profunda; and acetabular retroversion assessed by the presence of the crossover sign were associated with a contralateral slip in patients presenting with unilateral SCFE. We evaluated 250 patients with initial diagnosis of unilateral SCFE (average age, 12.5 ± 1.7 years), who had not undergone prophylactic fixation on the contralateral hip for a median follow-up of 49 months (interquartile range: 25-76 months). Endpoints were the development of a contralateral slip (70 patients, 28%) or skeletal maturity assessed by complete closure of the proximal femoral growth plate (180 patients, 72%). We measured the LCEA, Tönnis angle, ADR, and the coxa profunda sign on an anteroposterior pelvic radiograph. The crossover sign was assessed in 208 hips who had a secondary ossification center in the posterior acetabular rim. For each additional degree of LCEA, the odds of contralateral slip decreased 8% [odds ratio = 0.92; 95% confidence interval (CI), 0.87-0.98; P = 0.009]. Tönnis angle (P = 0.11), ADR (P = 0.20) and coxa profunda (p = 0.37) had no association with a contralateral slip. The presence of crossover sign increased two and half times the odds for a contralateral slip (odds ratio = 2.5; 95% CI = 1.12-5.64; P = 0.03). Acetabular retroversion, but not acetabular overcoverage or increased acetabular depth, was associated with contralateral SCFE development in patients with unilateral SCFE. Level of evidence: prognostic level II.

The acetabulum in healed Legg-Calvé-Perthes disease is cranially retroverted and associated with global reduction of femoral head coverage: a matched-cohort study

To evaluate the acetabular morphology in healed Legg–Calvé–Perthes disease after skeletal maturity using computed tomography (CT) scan and to compare with matched controls. We identified 33 (37 hips) patients with healed Legg–Calvé–Perthes disease and closed triradiate cartilage who underwent pelvic CT scan. Each patient was matched based on sex, age and side to a subject with no history of hip disease who had undergone pelvic CT evaluation because of abdominal pain. Both cohorts had 23 (70%) males and mean age of 16.4–16.5 ± 3.6 years. Two independent readers assessed lateral center-edge angle (LCEA), acetabular inclination angle (IA), acetabular depth-width ratio (ADR), acetabular version 10 mm below the dome (cranial) and at the acetabular center and anterior (AASA) and posterior acetabular sector angles (PASA). All measurements had good to excellent interobserver agreement (intraclass coefficients ≥ 0.87). The hips in the Legg–Calvé–Perthes disease cohort had a smaller mean ± standard deviation (SD) superior, anterior and posterior acetabular coverage as assessed by LCEA (13.2° ± 10.7° versus 28.2° ± 3.4°; P < 0.0001), IA (11.6° ± 6.7° versus 3.5° ± 2.8°; P < 0.0001), AASA (52.4° ± 9.5° versus 59.3° ± 5.0°; P = 0.001) and PASA (79.3° ± 5.9° versus 92.3° ± 5.5°; P < 0.0001) compared with controls. The acetabulum was shallower (ADR 287 ± 45 versus 323 ± 28; P = 0.0002) and the acetabular version was decreased cranially (0.4°±9.2° versus 8.2°±6.8°; P = 0.0002) and at the acetabular center (13.7°±5.1° versus 17.2° ±3.8°; P = 0.004) in Legg–Calvé–Perthes disease hips. After skeletal maturity, hips with healed Legg–Calvé–Perthes disease have shallower and more cranially retroverted acetabula, with globally reduced coverage of the femoral head compared with age-, sex- and side-matched control hips.

MRI Is Better Than CT Scan for Detection of Structural Pathologies After Traumatic Posterior Hip Dislocations in Children and Adolescents

BACKGROUND

Traumatic posterior hip dislocations in children and adolescents requires emergent closed reduction. Postreduction imaging is necessary to assess the concentricity of reduction and structural injuries to the hip. There is no a consensus for which imaging is a modality of choice in such condition. The purposes of this study are to describe magnetic resonance imaging (MRI) findings of traumatic posterior hip dislocations and to compare the effectiveness of MRI with computerized tomography (CT) in detecting structural abnormalities of the hip that impact patient management.

METHODS

This study is a retrospective review of imaging in traumatically dislocated hips in patients who were treated at our institution. All CT and MRI imaging were reviewed and specific osseous and soft tissue injuries documented by consensus among 2 musculoskeletal pediatric radiologists who interpreted the MRI and CT scans of each patient in a blinded manner.

RESULTS

In total, 27 patients (23 males, 4 females) with mean age of 12.5 years (range, 2 to 19 y) with postreduction MRI were evaluated. MRI findings revealed femoral head injuries in 17 (62.9%), posterior labral entrapments in 6 (22.2%), posterior labral tears in 17 (62.9%), posterior wall fractures in 15 (55.5%), fracture of the posterior unossified part of acetabulum in 4 (14.8%), and ligamentum teres injuries in 8 (29.6%). Of 16 patients who had postreduction CT scans, 6 (37.5%) had femoral head fractures, 9 (56.3%) had posterior wall fractures, and 8 (50%) had intra-articular osseous entrapments. All bony fractures and intra-articular entrapment could be seen on MRI imaging. In 16 patients with both CT and MRI, posterior acetabular injury was detected in 10/16 (62.5%) on MRI and 9/16 (56.3%) on CT. Three patients with entrapment of labrums identified on MRI could not be seen on CT scan. One patient with persistently unstable hip after reduction had an entrapped unossified portion of acetabular fracture which was seen on MRI but not on CT.

CONCLUSIONS

MRI is superior to CT scan for detection of structural injuries in children and adolescents with traumatic hip dislocation. The unique structural injuries included entrapment of posterior labrum and posterior unossified acetabular fractures could be seen only at MRI. These findings will impact surgical decision making of these injuries.

LEVEL OF EVIDENCE

Level IV.

Normal Glenoid Ossification in Pediatric and Adolescent Shoulders Mimics Bankart Lesions: A Magnetic Resonance Imaging-Based Study

PURPOSE

The purpose of this descriptive study was to define patterns of ossification and fusion of growth centers around the pediatric and adolescent glenoid as a function of age using 3-dimensional, frequency-selective, fat-suppressed spoiled gradient recalled echo magnetic resonance (MR) imaging sequences, with a particular focus on the anterior glenoid rim because of its clinical relevance as a potential confounder of glenohumeral instability.

METHODS

Picture Archiving and Communication System records at an urban academic tertiary care orthopaedic facility from October 2005 to December 2018 were queried for shoulder MRI in patients aged 9 to 17 years. Patients were excluded if they had any diagnoses that could alter glenoid development. All images were independently evaluated by a musculoskeletal fellowship-trained radiologist. Secondary ossification centers were characterized as cartilage anlage, ossified, or fused at 3 anatomic sites: the anterior glenoid rim, coracoid, and superior glenoid rim.

RESULTS

A total of 250 MR examinations (143 males, 107 females) were assessed in this study. The glenoid develops in a predictably sequential manner with ossification at the anterior glenoid rim lagging behind the coracoid and superior glenoid rim. The earliest age of anterior glenoid rim ossification was 11 years for both males (range 11-17) and females (range 11-12). Anterior glenoid rim ossification peaked at age 16 among males (34.8%, 8/23) and age 11 among females (27.3%, 3/11).

CONCLUSIONS

Glenoid ossification and fusion progress in a predictable and chronological manner. This pattern should be used as a guideline when interpreting pediatric shoulder MRI examinations. In particular, an anterior glenoid ossification center should not be confused with an anterior glenoid injury (e.g., Bankart lesion), particularly in males 11 to 17 years old and females 11 to 12 years old.

LEVEL OF EVIDENCE

IV (case series).

Early Reduction of Pediatric Traumatic Posterior Hip Dislocation Is Much More Important Than the Treatment Procedure

Traumatic hip dislocations are very rare in the pediatric population, and they are real emergent cases that can occur with minimal trauma. If they are not diagnosed immediately and reduction is not performed as soon as possible, they may cause problems such as avascular necrosis and degenerative arthritis. Performing reduction within the first 6 hours is of vital importance.We aim to present the functional outcomes and radiographic results of 2 pediatric traumatic hip dislocation cases with 36 months of follow-up who were treated with abduction orthosis after the reduction. We want to emphasize the importance of reduction time in the outcome of posterior traumatic hip dislocations followed with abduction orthesis even if there is a trend and suggestion to treat these patients with spica cast with the review of the recent literature.

Acetabular Retroversion and Decreased Posterior Coverage Are Associated With Sports-related Posterior Hip Dislocation in Adolescents

BACKGROUND

Leverage of the femoral head against the acetabular rim may lead to posterior hip dislocation during sports activities in hips with femoroacetabular impingement (FAI) deformity. Abnormal concavity of the femoral head and neck junction has been well described in association with posterior hip dislocation. However, acetabular morphology variations are not fully understood.

QUESTIONS/PURPOSES

The purpose of this study was to compare the acetabular morphology in terms of acetabular version and coverage of the femoral head in adolescents who sustained a posterior hip dislocation during sports and recreational activities with a control group of patients without a history of hip disease matched by age and sex.

METHODS

In this case-control study, we identified 27 adolescents with posterior hip dislocation sustained during sports or recreational activities who underwent a CT scan of the hips (study group) and matched them to patients without a history of hip disease being evaluated with CT for possible appendicitis (control group). Between 2001 and 2017, we treated 71 adolescents (aged 10-19 years old) for posterior hip dislocations. During the period in question, we obtained CT scans or MR images after closed reduction of a posterior hip dislocation. One patient was excluded because of a diagnosis of Down syndrome. Twenty-one patients who were in motor vehicle-related accidents were also excluded. Twelve patients were excluded because MRI was obtained instead of CT. Finally, three patients with no imaging after reduction and seven patients with inadequate CT reformatting were excluded. Twenty-seven patients (38%) had CT scans of suitable quality for analysis, and these 27 patients constituted the study group. We compared those hips with 27 age- and sex-matched adolescents who had CT scans for appendicitis and who had no history of hip pain or symptoms (control group). One orthopaedic surgeon and one pediatric musculoskeletal radiologist, not invoved in the care of the patients included in the study, measured the lateral center-edge angle, acetabular index, acetabular depth/width ratio, acetabular anteversion angle (10 mm from the dome and at the level of the center of the femoral heads), and the anterior and posterior sector angles in the dislocated hip; the contralateral uninvolved hip of the patients with hip dislocations; and both hips in the matched control patients. Both the study and control groups had 25 (93%) males with a mean age of 13 (± 1.7) years. Inter- and intrarater reliability of measurements was assessed with intraclass correlation coefficient (ICC). There was excellent reliability (ICC > 0.90) for the acetabular anteversion angle measured at the center of the femoral head, the acetabular version 10 mm from the dome, and the posterior acetabular sector angle.

RESULTS

The mean acetabular anteversion angle (± SD) was lower in the study group at 10 mm from the acetabular dome (-0.4° ± 9° versus 4° ± 4°; mean difference -5°; 95% confidence interval [CI], -9 to -0.3; p = 0.015) and at the center of the femoral heads (10° ± 5° versus 14° ± 4°; mean difference -3°; 95% CI, -6 to -0.9; p = 0.003). A higher proportion of acetabula was severely retroverted in the study group (14 of 27 [52%]; 95% CI, 33%-71% versus four of 27 [15%]; 95% CI, 1%-28%; p = 0.006). The mean posterior acetabular sector angle was lower in the study group (82° ± 8° versus 90° ± 6°; mean difference -8°; 95% CI, -11 to -4; p < 0.001), whereas no difference was found for the anterior acetabular sector angle (65° ± 6° versus 65° ± 7°; mean difference 0.3°; 95% CI, -3 to 4; p = 0.944). There was no difference for the lateral center-edge angle (27° ± 6° versus 26° ± 5°; p = 0.299), acetabular index (5° ± 3° versus 6 ± 4°; p = 0.761), or acetabular depth/width ration (305 ± 30 versus 304 ± 31; p = 0.944) between groups. Acetabular anteversion angle at the center of the femoral heads (11° ± 4° versus 14° ± 4°; p = 0.006) and the posterior acetabular sector angle (86° ± 7 ° versus 91° ± 6°; p = 0.007) were lower in the contralateral uninvolved hips compared with control hips.

CONCLUSIONS

Decreased acetabular anteversion angle and posterior acetabular coverage of the femoral head were associated with posterior dislocation of the hip in adolescents with sports-related injury even in the absence of a high-energy mechanism. Further studies are necessary to clarify whether a causative effect exists between acetabular and femoral morphology and the dislocation of the hip in patients with sports-related injuries.

LEVEL OF EVIDENCE

Level III, prognostic study.

Acetabular morphology in slipped capital femoral epiphysis: comparison at treatment onset and skeletal maturity

PURPOSE

To investigate changes in acetabular morphology during the follow-up of slipped capital femoral epiphysis (SCFE) and search for factors associated with acetabular dysplasia at skeletal maturity.

METHODS

We evaluated 108 patients with unilateral SCFE (mean age at slip, 12.3 years sd 1.7) to skeletal maturity, with a minimum follow-up of two years (median 4.5 years; interquartile range 3.2 to 6.2). Acetabular parameters obtained from initial and most recent radiographs included the lateral centre-edge angle (LCEA), Tönnis angle (TA) and acetabular depth-width ratio (ADR). Acetabular dysplasia was considered for LCEA < 20° or TA > 10°. Femoral parameters consisted of the most recent head diameter, neck-shaft angle, neck length, articulotrochanteric distance and alpha angle.

RESULTS

At SCFE onset, the affected hip showed a slightly lower LCEA (26.4° sd 6.1° versus 27.3° sd 5.7°; p = 0.01) and ADR (330 sd 30 versus 340 sd 30; p < 0.001) compared with the uninvolved hip. At final follow-up, the affected hip showed lower LCEA (24.5° sd 7.6° versus 28.8°sd 6.6°; p < 0.001) and ADR (330 sd 40 versus 350 sd 40; p < 0.001), and TA was larger (5.5° sd 5.4° versus 2.3° sd 4.2°; p < 0.001) compared with the uninvolved hip. Acetabular dysplasia was observed in 27 (25%) of 108 hips with SCFE. Femoral head overgrowth, age at slip and SCFE severity were independent factors associated with acetabular dysplasia (p < 0.05).

CONCLUSION

Acetabular coverage and depth are not increased in SCFE, and the acetabular coverage tends to decrease up to skeletal maturity. A potential disturbance in the acetabular growth and remodelling exists mainly for young children with severe SCFE, and a potential for acetabular insufficiency may be observed at the diagnosis and follow-up of SCFE.

LEVEL OF EVIDENCE

Prognostic Level IV.

Ischemic femoral head osteonecrosis in a piglet model causes three dimensional decrease in acetabular coverage

Legg-Calve-Perthes disease (LCPD) is a childhood form of ischemic osteonecrosis marked by development of severe femoral head deformity and premature osteoarthritis. The pathogenesis of femoral head deformity has been studied extensively using a piglet model of ischemic osteonecrosis, however, accompanying acetabular changes have not been investigated. The purpose of this study was to determine if acetabular changes accompany femoral head deformity in a well-established piglet model of LCPD and to define the acetabular changes using three dimensional computed tomography (3-D CT) and modeling. Twenty-four piglets were surgically induced with ischemic osteonecrosis on the right side. The contralateral hip was used as control. At 8 weeks postoperative, pelvi were retrieved and imaged with CT. Custom software was used to measure acetabular morphologic parameters on 3-D CT images. Moderate to severe femoral head deformities were present in all animals. Acetabula with accompanying femoral head deformity had a significant decrease in acetabular version and tilt (p < 0.001) and in coverage angle in the superior, posterior, and inferior quadrants (p < 0.05). These findings indicate that the development of femoral head deformity following ischemic osteonecrosis produces specific and predictable changes to the shape of the acetabulum. Acetabular changes described in patients with LCPD were observed in the piglet model. This model may serve as a valuable tool to elucidate the relationship between femoral head and acetabular deformities. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1173-1177, 2018.

Analysis of Acetabular Ossification From the Triradiate Cartilage and Secondary Centers

BACKGROUND

Acetabular development is a complex process that involves both endochondral growth from the triradiate cartilage (TRC) and intramembranous growth from the primary and secondary ossification centers of the innominate bones. Ponseti and others have described these centers including their contribution toward the development of normal acetabular shape. Prior studies have not utilized advanced imaging to study the appearance and closure of these secondary centers. The purpose of this study was to determine the chronological age at which the secondary ossification centers of the acetabulum appear and close and where there are any sex differences.

METHODS

Patients who underwent abdominal and pelvic computed tomography (CT) scans between January 2009 and December 2014 at a pediatric hospital were retrospectively reviewed. Patients between age 6 and 16 years with adequate imaging of acetabulum were included. CT scans were assessed for the appearance and closure of the 3 acetabular secondary ossification centers [anterior (os pubis), superior (os ilium), and posterior (os ischium)] and closure of the TRC.

RESULTS

A total of 159 CT scans met inclusion criteria (66 males and 93 females). The median age of appearance of the secondary ossification centers was: posterior (10.1 females, 12.8 males), anterior (10.7 females, 13.4 males), and superior (11.1 females, 13.6 males). The median age of closure of the secondary ossification centers was: posterior (12.8 females, 13.6 males), anterior (12.8 females, 13.9 males), superior (14.5 females, 13.9 males), and TRC (14.5 females, 14.3 males). Most ossification centers in females appeared and closed approximately 2 to 3 years before males.

CONCLUSIONS

Secondary ossification centers in the acetabulum appear sequentially (first posterior, then anterior, then superior), with almost all centers closing just before TRC. Closure occurs earlier in females than males. Knowledge of these centers and their closure patterns allows better radiologic readings (especially CT studies) and understanding of acetabular growth, allowing more informed management of childhood hip conditions including dysplasia, trauma, and over-use sports injuries.

LEVEL OF EVIDENCE

Level III-Diagnostic.

Acetabular Version Increases After Closure of the Triradiate Cartilage Complex

BACKGROUND

Although the etiology of primary femoroacetabular impingement (FAI) is considered developmental, the underlying pathogenic mechanisms remain poorly understood. In particular, research identifying etiologic factors associated with pincer FAI is limited. Knowledge of the physiologic growth patterns of the acetabulum during skeletal maturation might allow conclusions on deviations from normal development that could contribute to pincer-related pathomorphologies.

QUESTIONS/PURPOSES

In a population of healthy children, we asked if there were any differences related to skeletal maturation with regard to (1) acetabular version; (2) acetabular depth/width ratio; and (3) femoral head coverage in the same children as assessed by MRIs obtained 1 year apart.

METHODS

We prospectively compared 129 MRIs in 65 asymptomatic volunteers without a known hip disorder from a mixed primary/high school population (mean age, 12.7 years; range, 7-16 years). All participants underwent two MRI examinations separated by a minimum interval of 1 year. Based on the status of the triradiate cartilage complex (open versus closed [TCC]), all hips were allocated to the following groups: "open-open" = open TCC at both MRIs (n = 45 hips [22 bilateral]); "open-closed" = open TCC at initial and closed TCC at followup MRI (n = 26 hips [13 bilateral]); and "closed-closed" group = closed TCC at both MRIs (n = 58 hips [29 bilateral]). We assessed acetabular version in the axial plane at five different locations (5, 10, 15, 20 mm below the acetabular dome and at the level of the femoral head) as well as three-dimensional (3-D) acetabular depth/width ratio and 3-D femoral head coverage on six radial MRI sequences oriented circumferentially around the femoral neck axis. Using analysis of variance for multigroup comparisons with Bonferroni adjustment for pairwise comparisons, we compared the results between the initial and followup MRI examinations and among the three groups.

RESULTS

Acetabular version was increased in hips of the "open-closed" group at the followup MRI compared with the initial MRI at 5 mm (-6 ± 4.6 [95% confidence interval {CI}, -7.6 to -3.6] versus -1 ± 5.0 [95% CI, -3.3 to 0.7]; p < 0.001), 10 mm (0 ± 4.0 [95% CI, -1.6 to 2.1] versus 7 ± 4.6 [95% CI, 4.4-8.7]; p < 0.001), and 15 mm (8 ± 5.0 [95% CI, 6.1-10.2] versus 15 ± 4.6 [95% CI, 13.3-17.4]; p < 0.001) below the acetabular dome. Acetabular version did not change between the initial and followup MRI in the "open-open" and "closed-closed" groups. Independently of the groups, acetabular version was increased in all hips with a fused TCC compared with hips with an open TCC (mean difference measured at 5 mm below the acetabular dome at initial MRI examination: 2° ± 5.9° [95% CI, 0.2°-3.4°] versus -9° ± 4.4° [95% CI, -9.9° to -7.8°]; p < 0.001; at followup MRI examination: 1° ± 5.7° [95% CI, 0.1°-2.7°] versus -9° ± 3.8° [95% CI, -10° to -7.6°]; p < 0.001). Both acetabular depth/width ratio and femoral head coverage did not differ among the groups or between the initial and followup MRI examinations within each group.

CONCLUSIONS

Although acetabular depth/width ratio and femoral head coverage remain relatively constant, acetabular version increases with advancing skeletal maturity. There seems to be a relatively narrow timeframe near physeal closure of the TCC within which acetabular orientation changes to more pronounced anteversion. Further studies with greater numbers and longer followup periods are required to support these findings and determine whether such version changes may contribute to pincer-type pathomorphologies.

LEVEL OF EVIDENCE

Level II, prospective study.

Surgical Hip Dislocation for the Treatment of Intra-Articular Injuries and Hip Instability Following Traumatic Posterior Dislocation in Children and Adolescents

BACKGROUND

Traumatic posterior hip dislocation in children is a rare injury that typically is treated with closed reduction. Surgical treatment is typically recommended for nonconcentric reduction with joint space asymmetry with entrapped labrum or an osteochondral fragment. The surgical hip dislocation (SHD) approach allows for full assessment of the acetabulum and femoral head and has been our preferred surgical strategy. The purpose of this study was to (1) describe the intra-articular pathologic findings seen at the time of SHD; and (2) to investigate hip pain, function, and activity level of a cohort of children and adolescents after open treatment of a posterior hip dislocation using the SHD approach.

METHODS

Following IRB approval, 23 patients who sustained a traumatic posterior hip dislocation between January 2009 and December 2013 were identified. In 8/23 (34.8%) patients there was evidence of nonconcentric reduction after closed treatment and surgical treatment was performed using the SHD approach. Seven male and 1 female (mean age, 11.2 y; range, 6 to 14.6 y) were followed for an average of 28 months (range, 13 to 67 mo). The modified Harris Hip Score (mHHS) and the University of California Los Angeles activity score assessed clinical hip outcome and activity level at minimum of 1 year after surgery.

RESULTS

Six patients were treated after an acute trauma, whereas 2 were treated after recurrent dislocations. Five patients were involved in motor vehicle accidents and 3 in sports-related injuries. Intraoperative findings include posterior labral avulsion in all patients, fracture of the cartilaginous posterior wall (n=3), and femoral head chondral injuries (n=5) and fracture (n=1). The labral root was repaired using suture anchor technique in 7/8 patients and resected in 1. In 2 patients, labral repair was complemented by screw fixation of the posterior wall. All but one patient (mHHS=94) reported maximum mHHS. The University of California Los Angeles activity score was 10 for 5/8 patients and 7 in 3 patients. No case of femoral head osteonecrosis was noted. One patient developed an asymptomatic heterotopic ossification.

CONCLUSIONS

When open reduction is recommended for the treatment of intra-articular pathologies and hip instability following traumatic dislocation of the hip in children and adolescents, the SHD is an excellent approach that allows surgical correction of the damaged bony and soft-tissue structures including repair of the capsule-labral complex, and reduction and internal fixation of the cartilaginous posterior wall and femoral head fractures.

LEVEL OF EVIDENCE

Level IV.

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.

Reconteo de los huesos del esqueleto humano

<p>Introducción. Se ha contemplado la idea de que el esqueleto humano posee cierto número de huesos, asignando siempre la misma cantidad de 206 estructuras; en este conteo no se tienen en cuenta sus clasificaciones, las sinostosis ni si se presentan o no variaciones anatómicas. Objetivos. Proponer un nuevo conteo de los huesos del esqueleto humano a partir de la clasificación habitual y renovar la terminología ósea tradicional. Materiales y métodos. Se estudiaron textos de Anatomía empleados en la enseñanza y aprendizaje de las ciencias para la salud, se exploró en diferentes bases de datos enfocadas en el campo de la medicina y, fundamentalmente, se adoptó la terminología apropiada del texto Terminologia Anatomica: International Anatomical Terminology del Comité Internacional Federativo de Terminología Anatómica. Resultados. Se expone la clasificación tradicional del esqueleto humano en axial y apendicular contando cada uno de sus componentes. Conclusión. Se obtiene un nuevo conteo óseo donde se desagrupan el esternón en manubrio, cuerpo y proceso xifoides; en el sacro y el cóccix se cuentan sus vértebras independientes y el coxal se desagrupa contándose independientemente el ilion, el isquion y el pubis. No se tienen en cuenta huesos sesamoideos ni intersuturales.</p>

The 'triradiate bump': a novel radiographic sign that may confound assessment of acetabular retroversion

PURPOSE

The triradiate cartilage transiently projects medially within the pelvic brim around the time of triradiate closure, mimicking the ischial spine sign. The purpose of this study was to characterize this newly identified radiographic sign using a longitudinal radiographic study.

METHODS

We identified 72 subjects from a longitudinal radiographic study of healthy adolescents, each with at least four consecutive, annual anterior-posterior radiographs of the left hip, including physeal closure. Images were reviewed to identify the presence of the triradiate bump, the year it was most prominent, and the number of years relative to triradiate closure after which it had completely remodeled.

RESULTS

The transient medial projection of the triradiate cartilage (triradiate bump) was identified in 26/40 (65 %) females and 22/32 (69 %) males (p = 0.74). The medial projection of the triradiate cartilage was most prominent at 10.8 ± 0.8 years of age in females and 12.6 ± 0.7 years of age in males (p < 0.001). The triradiate cartilage projected medially a mean of 4.7 ± 0.8 or 5.1 ± 1.4 mm for females and males, respectively (p = 0.29), but remodeled completely in all cases around triradiate closure.

CONCLUSIONS

The transient medial projection of the triradiate cartilage within the pelvic brim, the 'triradiate bump sign', is a common radiographic finding in healthy adolescents around the time of closure of the triradiate cartilage that may mimic the ischial spine sign. These two signs can be distinguished as the projection of the ischial spine is located more inferiorly within the pelvic brim and the triradiate bump has a horizontal limb of radiolucency extending to its medial border.

Capital Femoral Growth Plate Extension Predicts Cam Morphology in a Longitudinal Radiographic Study

BACKGROUND

Recent evidence has suggested that cam morphology may be related to alterations in the capital femoral growth plate during adolescence. The purpose of this study was to evaluate the relationship between capital femoral growth plate extension and cam morphology in a longitudinal radiographic study.

METHODS

We used a historical, longitudinal radiographic collection to identify 96 healthy adolescents (54 boys and 42 girls) with at least 5 consecutive annual radiographs of the left hip including closure of the capital femoral physis. We reviewed 554 anteroposterior radiographs of the left hip to measure the anteroposterior modification of the alpha angle of Nötzli and of the superior epiphyseal extension ratio (EER), measured as the ratio of extension of the capital femoral epiphysis down the femoral neck relative to the diameter of the femoral head. Measurements were made at 3 points in femoral head maturation corresponding to the Oxford bone age (OBA) femoral head stages 5, 6, and 7/8.

RESULTS

There was a mean increase in the anteroposterior alpha angle (10.7° ± 14.0°) and EER (0.12 ± 0.08) between OBA stages 5 and 7/8, corresponding to maturation and closure of the capital femoral physis. There was a positive correlation between the final anteroposterior alpha angle and both the final EER (r = 0.60) and the change in the EER (r = 0.58). A receiver operating characteristic curve generated to predict an anteroposterior alpha angle of ≥78° through the EER demonstrated an area under the curve of 0.93, indicating that an increasing EER had excellent diagnostic accuracy for predicting concurrent cam morphology.

CONCLUSIONS AND CLINICAL RELEVANCE

Superior epiphyseal extension was directly and temporally associated with an increase in anteroposterior alpha angle and more cam-like morphology. This alteration in the capital femoral epiphysis occurred immediately before physeal closure (OBA stage 7/8). Given the association of epiphyseal extension with activities that increase shear forces across the physis, we proposed that epiphyseal extension may be an adaptive mechanism to stabilize the physis and prevent slipped capital femoral epiphysis.

How Often Does Femoroacetabular Impingement Occur After an Innominate Osteotomy for Acetabular Dysplasia?

BACKGROUND

Femoroacetabular impingement is increasingly recognized as a cause of hip pain but its incidence after an innominate osteotomy for the correction of acetabular dysplasia has not been determined. This information would be essential for the orthopaedic surgeon because it has the potential to produce a poor outcome in the long term when trying to balance acetabular instability and overcorrection.

QUESTIONS/PURPOSES

The purposes of our study were (1) to determine the frequency with which clinically relevant femoroacetabular impingement (FAI) occurs after an innominate osteotomy for the treatment of acetabular dysplasia; (2) to determine risk factors for the development of FAI; and (3) to compare postoperative radiographic and clinical outcomes in patients having undergone an innominate osteotomy for the correction of acetabular dysplasia both with and without FAI.

METHODS

This was a retrospective review of 154 hips (132 patients) that had undergone an innominate osteotomy for acetabular dysplasia and were evaluated at a minimum followup of 10 years (mean = 12 years). Mean age at the time of surgery was 3 years, 114 hips had a concomitant open reduction, and 54 hips also had femoral shortening. One hundred eight hips had a Salter osteotomy and 46 had a Pemberton osteotomy. Radiographs were analyzed to determine the lateral center-edge angle (CE angle) and the presence of a crossover sign. The diagnosis of FAI was established when the CE angle was greater than 40°, there was a positive crossover sign, and the patient had groin pain when flexing the hip less than 90°. Comparisons between nonparametric variables were performed with a Mann-Whitney's U test. Categorical variables were compared with a chi-square test. Change in acetabular index (correction) was dichotomized considering 20° of correction as the cutoff point. Association is presented as odds ratio (95% confidence interval), and logistic regression was performed.

RESULTS

According to our criteria, 18 of 154 hips had FAI (12%). Of the 18 patients with FAI, 10 had undergone a Pemberton osteotomy (10 of 46 [22%]) and eight a Salter osteotomy (eight of 108 [7%]). A change in the postoperative acetabular index greater than 20° was associated with a greater likelihood of developing FAI. The mean postoperative acetabular index was lower for the group with FAI, for whom it was 20°, compared with the group without FAI, for whom it was 27° (p = 0.04). The mean Iowa Hip Score for the group with FAI was 85, whereas for those without FAI, it was 93 (p = 0.03).

CONCLUSIONS

FAI is not common after an innominate osteotomy for the treatment of acetabular dysplasia; however, overcorrection is related to a higher incidence. When FAI is present, it can affect the outcome. Overcorrection should be avoided when performing an innominate osteotomy for the treatment of acetabular dysplasia because it can create iatrogenic FAI and have an adverse effect on outcome.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Anatomical "C"-shaped double-bundle versus single-bundle anterior cruciate ligament reconstruction in pre-adolescent children with open growth plates

PURPOSE

To analyse the clinical, rotational and radiological (MRI) results of paediatric anatomical "C-shaped" double-bundle (DB) anterior cruciate ligament (ACL) reconstruction with anteromedial and posteromedial bundle compared to single-bundle (SB) ACL reconstruction.

METHODS

Between 2008 and 2014, 57 consecutive patients received a paediatric ACL reconstruction with open physis and were allocated into two groups, according to the surgical procedure. Transepiphyseal SB technique was used until 2012 and DB consecutively thereafter. Follow-up consisted of a clinical evaluation with assessment of the International Knee Documentation Committee (IKDC) form, the Lysholm knee score, Tegner activity score, KT-1000 arthrometer evaluation, VAS Scores for satisfaction, MRI and testing of rotational stability using a robotic system.

RESULTS

The mean time from ACL reconstruction to follow-up was 48.1 ± 15.8 in the SB group (n = 17) and 23.1 ± 13.2 in the DB group (n = 16; p < 0.001). No differences were found in the subjective scores. Biomechanically, there were significant differences identified in the KT-1000 (p < 0.03) and total tibial axial rotation (p < 0.04) when evaluating the reconstructed knee only. Ten of 17 (59%) of the SB patients had a Joint Play Area within the acceptable range of the median healthy knee value compared to 100 % in the DB group. Decreased patient satisfaction was associated with increased total tibial axial rotation. No growth disturbance was observed. Overall, 98% of patients were reached and either examined or interviewed. Re-rupture rate was 3 of 21 (14.3%) for DB and 9 of 35 (25.7%) for SB. All but one re-ruptures (92%) happened in the first 16 postoperative months independent of technique.

CONCLUSIONS

The re-rupture rate after pre-adolescent ACL reconstruction is too high both historically and in this mixed cohort. Anatomical transepiphyseal DB ACL reconstruction with open physis may result in a reduction in this re-rupture rate, which may be related to a tighter control of the Joint Play Area. While subjective clinical results were similar between SB and DB, decreased patient satisfaction was associated with increased total tibial axial rotation in the entire cohort. Despite the need for two transepiphyseal tunnels in the DB technique, there did not appear to be an increased risk in growth plate disturbance. Transepiphyseal DB ACL reconstruction appears to be a reasonable alternative to current techniques in pre-adolescent children with an ACL rupture.

LEVEL OF EVIDENCE

IV.

Femoroacetabular impingement in children and adolescents

PURPOSE OF REVIEW

The present review discusses the etiology, clinical presentation, and management of femoroacetabular impingement (FAI) in the pediatric population, including etiologic and diagnostic controversies, management options, and outcomes.

RECENT FINDINGS

New evidence demonstrates conflicting results regarding how and when primary FAI develops in relation to skeletal maturity. Recent studies also discuss the effects of sex, race, and sports on FAI development and radiographic considerations in the pediatric population. Recent literature demonstrates good to excellent outcomes in the operative management of FAI in children and adolescents.

SUMMARY

FAI is a source of pediatric hip pain and can occur primarily or secondarily. It is characterized by anterior hip pain, made worse with flexion activities, decreased hip internal rotation, and a positive impingement sign. Pathologic values for radiographic measures of FAI are not clearly defined in the pediatric population. As FAI is a risk factor for osteoarthritis, early intervention in specific patients may be indicated. Hip arthroscopy, surgical hip dislocation, or combined mini-open and arthroscopic approaches are utilized, with good to excellent short, and mid-term functional results. Further study is required in the pediatric population to identify potential preventive strategies, to delineate the pathologic radiographic values of FAI, to define specific indications for operative management, and to examine long-term outcomes to determine optimal management.

Surgical Hip Dislocation is Safe and Effective Following Acute Traumatic Hip Instability in the Adolescent

BACKGROUND

A traumatic hip dislocation in the pediatric patient is a rare but potentially catastrophic injury. The purpose of this study was to review our early clinical results and radiographic morphology of hips treated with a surgical hip dislocation (SHD) approach for intra-articular hip pathology resulting from traumatic instability in pediatric and adolescent patients.

METHODS

This is a retrospective analysis of a consecutive series of patients presenting with nonconcentric reduction after traumatic hip instability. All patients were treated with a transtrochanteric SHD with concomitant procedures based on intra-articular findings. Radiographic evaluations and Harris Hip Scores were completed at final follow-up.

RESULTS

Eleven male patients, mean age of 12.3 years (range, 9.3 to 16.1 y) and mean body mass index 19.6 kg/m (range, 15.4 to 28.0 kg/m). Intraoperative findings included: labral tear (8), femoral cartilage injury (5), acetabular rim fracture (4), acetabular cartilage delamination (3), loose body (2), and femoral head osteochondral fracture (1). Postoperatively, 1 patient developed a transient peroneal nerve palsy. At a mean 24.5 months (range, 12.0 to 48.1 mo) postoperatively, no hips have radiographic evidence of osteonecrosis. The mean lateral center edge angle was 20 degrees (range, 9 to 38 degrees) with 6 hips of <20 degrees; mean acetabular index 9 degrees (range, -2 to 23 degrees) with 5 hips of >10 degrees; mean α-angle 56 degrees (range, 48 to 62 degrees) with 6 hips of >55 degrees; mean acetabular version 12 degrees (range, 8 to 16 degrees) with 8 hips of <15 degrees. At 1-year follow-up, the mean Harris Hip Score was 95.8 (range, 84.7 to 100).

CONCLUSIONS

Early results suggest that SHD is a safe approach to treat an incomplete reduction following posterior hip instability and is effective for identification and treatment of acute intra-articular pathology. Acetabular dysplasia, relative acetabular retroversion, and/or decreased femoral offset may be risk factors for posterior hip instability in adolescents.

LEVEL OF EVIDENCE

Level IV.

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.

Sex Differences in Cartilage Topography and Orientation of the Developing Acetabulum: Implications for Hip Preservation Surgery

BACKGROUND

Increased attention is being placed on hip preservation surgery in the early adolescent. An understanding of three-dimensional (3-D) acetabular development as children approach maturity is essential. Changes in acetabular orientation and cartilage topography have not previously been quantified as the adolescent acetabulum completes development.

QUESTIONS/PURPOSES

We used a novel 3-D CT analysis of acetabular development in children and adolescents to determine (1) if there were sex-specific differences in the growth rate or surface area of the acetabular articular cartilage; (2) if there were sex-specific differences in acetabular version or tilt; and (3) whether the amount of version and tilt present correlated with acetabular coverage.

METHODS

We assessed acetabular morphology in 157 patients (314 hips); 71 patients were male and 86 were female. Patient ages ranged from 8 years to 17 years. A 3-D surface reconstruction of each pelvis was created from CT data using MIMICs software. Custom MATLAB software was used to obtain data from the 3-D reconstructions. We calculated articular surface area, acetabular version, and acetabular tilt as well as novel measurements of acetabular morphology, which we termed "coverage angles." These were measured in a radial fashion in all regions of the acetabulum. Data were organized into three age groups: 8 to 10 years old, 10 to 13 years old, and 13 to 17 years old.

RESULTS

Male patients had less acetabular anteversion in all three age groups, including at maturity (7° versus 13°, p<0.001; 10° versus 17°, p<0.001; 14° versus 20°, p<0.001). Males had less acetabular tilt in all three age groups (32° versus 34°, p=0.03; 34° versus 38°, p<0.001; 39° versus 41°, p=0.023). Increases in anteversion correlated with increased posterior coverage angles (r=0.805; p<0.001). Increases in tilt were correlated with increases in superior coverage angles (r=0.797; p<0.001). The posterosuperior regions of the acetabulum were the last to develop and this process occurred earlier in females compared with males. Articular surface area increased from 18 (8-10 years) to 24 cm(2) (13-17 years) in males and from 17 (8-10 years) to 21 cm(2) (13-17 years) in females. [corrected]. Articular surface area was higher in males beginning in the 10- to 13-year-old age group (p=0.001).

CONCLUSIONS

Using a novel technique to analyze acetabular morphology, we found that acetabular development occurs earlier in females than males. The posterosuperior region of the acetabulum is the final region to develop. The articular cartilage surface area and articular cartilage coverage of the femoral head are increasing in addition to total coverage of the femoral head during the final stages of acetabular development.

LEVEL OF EVIDENCE

Level III, prognostic study.

Increased Lateral Tibial Slope Is a Risk Factor for Pediatric Anterior Cruciate Ligament Injury: An MRI-Based Case-Control Study of 152 Patients

BACKGROUND

Increased posterior tibial slope is associated with increased risk of anterior cruciate ligament (ACL) injury in adults. A similar association has not been rigorously examined in children and adolescents.

PURPOSE

To determine whether alterations in posterior tibial slope are associated with ACL tears in pediatric and adolescent patients and to quantify changes in tibial slope by age.

STUDY DESIGN

Case-control study; Level of evidence, 3.

METHODS

Magnetic resonance imaging (MRI) studies of the knee were reviewed by 3 raters blinded to each other in a 1:1 sample of cases and age- and sex-matched controls. A total of 76 skeletally immature ACL-injured knees were compared with 76 knees without ACL injury; the mean age of the study population was 14.8 ± 1.3 years. The posterior slope of the articular surface of the medial tibial plateau and lateral tibial plateau was measured by use of a method similar to that used in previous studies in adult populations. The current study technique differed in that the slope was measured on the cartilage surface, not the subchondral bone. Comparisons between knees were made with t tests, and Spearman correlation analysis was used to assess changes in tibial slope with advancing age.

RESULTS

Increased slope of the lateral tibial plateau (LTS) was significantly increased in ACL-injured patients compared with controls (5.7° ± 2.4° vs 3.4° ± 1.7°; P < .001). There was no statistically significant difference in the slope of the medial tibial plateau (MTS) in the ACL-injured and control knees (5.4° ± 2.2° vs 5.1° ± 2.3°; P = .42). There was no difference in LTS between male and female patients (4.46° vs 4.58°; P = .75). Receiver operating characteristic (ROC) analysis of the LTS revealed that a posterior tibial slope cutoff of >4° resulted in a sensitivity of 76% and a specificity of 75% for predicting ACL tears in this cohort. Spearman correlation analysis revealed that MTS and LTS decreased, or flattened, by 0.31° (P = .028, correlation coefficient r = -0.18) and 0.37° (P = .009, correlation coefficient r = -0.21) per year, respectively, as adolescents age.

CONCLUSION

The LTS was significantly associated with an increased risk of ACL injury in pediatric and adolescent patients. The MTS was not associated with risk of injury. Posterior slope was found to decrease, or flatten, with age. A cutoff of >4° for the posterior slope of the lateral compartment is 76% sensitive and 75% specific for predicting ACL injury in this cohort. The LTS did not influence the incidence of ACL injury differently between sexes.

How do acetabular version and femoral head coverage change with skeletal maturity?

BACKGROUND

Normal changes in acetabular version over the course of skeletal development have not been well characterized. Knowledge of normal version development is important because acetabular retroversion has been implicated in several pathologic hip processes.

QUESTIONS/PURPOSES

The purpose of this study was to characterize the orientation of the acetabulum by measuring (1) acetabular version and (2) acetabular sector angles in pediatric patients during development. We also sought to determine whether these parameters vary by sex in the developing child.

METHODS

We evaluated CT images of 200 hips in 100 asymptomatic pediatric patients (45 boys, 55 girls; mean age, 13.5 years; range, 9-18 years) stratified by the status of the triradiate physis and sex. We determined the acetabular anteversion angle at various levels in the axial plane as well as acetabular sector angles at five radial planes around the acetabulum.

RESULTS

For both genders, anteversion angle was greater for the closed physis group throughout all levels (p < 0.001) and both open and closed physis groups were more anteverted as the cut moved caudally away from the acetabular roof (p < 0.001). At the center of the femoral head, the mean anteversion angle (± SD) in girls was 15° ± 3° in the open group and 19° ± 5° in the closed group (p < 0.001). In boys, the mean anteversion angle increased from 14° ± 4° in the open group to 19° ± 4° in the closed group (p = 0.003). In the superior, posterosuperior, and posterior planes, the acetabular sector angles were greater in the closed compared with the open physis group for both boys and girls with the largest increase occurring in the male posterosuperior plane (approximately 20°) (all p < 0.05).

CONCLUSIONS

This study demonstrates that acetabular anteversion and acetabular sector angles in both male and female subjects increase with skeletal maturity as a result of growth of the posterior wall. This suggests that radiographic appearance of acetabular retroversion may not be attributable to overgrowth of the anterior wall but rather insufficient growth of the posterior wall, which has clinical treatment implications for pincer-type impingement.

The effect of femoral and acetabular version on clinical outcomes after arthroscopic femoroacetabular impingement surgery

BACKGROUND

The impact of proximal femoral and combined femoral and acetabular version on patient-reported outcomes after arthroscopic surgery for femoroacetabular impingement (FAI) remains undefined. The purpose of this study was to identify associations of proximal femoral version as well as combined version (McKibbin index) with disease-specific, validated, patient-reported outcomes following arthroscopic correction of symptomatic FAI.

METHODS

A prospective hip arthroscopy registry was utilized to evaluate 243 patients who underwent arthroscopic surgery to correct FAI. Femoral version and the McKibbin index were measured prospectively on preoperative computed tomography scans. Disease-specific, patient-reported outcomes included the modified Harris hip score (mHHS) and the Hip Outcome Score (HOS) ADL (Activities of Daily Living) and Sports subscales. Disease impact on quality of life was determined with use of the International Hip Outcome Tool (iHOT-33). Comparative analyses were used to evaluate the impact of femoral version on changes in patient-reported outcome scores; multiple regression was used to adjust for potential confounders.

RESULTS

The patient cohort contained 243 patients (123 female and 120 male) with a mean age of 29.2 years and a mean postoperative follow-up of twenty-one months (range, twelve to forty-two months). The cohort experienced significant improvements (p < 0.001) in all patient-reported outcome measures, with most patients improving by at least the minimal clinically important difference for all of these measures. The mean improvement was 20 points for the mHHS, 15 for the HOS ADL, 23 for the HOS Sports, and 23 for the iHOT-33. When stratified by femoral version, the postoperative improvements in patients with relative femoral retroversion (<5° anteversion) were clinically important but of significantly smaller magnitude than those in the other version groups. We did not find any associations between the McKibbin index and any patient-reported outcomes.

CONCLUSIONS

Although clinically important improvements can be expected after arthroscopic FAI surgery in all femoral version groups, patients with relative femoral retroversion (<5° femoral anteversion) may experience less improvement than those with normal or increased version.