Secondary Ossification Center Appearance and Closure in the Pelvis and Proximal Femur

Pediatric Pelvis

The development of the pelvis follows a predictable pattern of ossification that involves the maturation of bone, synchondroses, and apophyses. These growth centers appear and close at distinct times during skeletal maturity and give rise to structural changes in the pelvis that can be distinctively appreciated on various imaging modalities. Accurate interpretation of radiologic images requires knowledge of skeletal development because the varying appearance of the maturing pediatric pelvis may be mistaken for pathology. In addition, many normal features within the pelvis can be erroneously perceived as injury. This article incorporates a multimodality review of normal pelvic maturation, a discussion of developmental variants, and a description of common injuries unique to the pediatric pelvis.

Ischiofemoral Impingement Due to an Undiagnosed Pelvic Avulsion Fracture

ABSTRACT

Ischial tuberosity (IT) avulsion fractures are an uncommon cause of injuries in athletes. In this case, a 26-year-old female suffering from posterior right hip pain for over a decade presented with debility and a decrease in athletic function. Notable history included a hamstring strain while sprinting in elementary school. Clinical examination suggested hamstring tendinopathy and ischiofemoral impingement (IFI). Magnetic resonance imaging (MRI) revealed a chronic, fragmented, IT apophyseal avulsion fracture with ischial bursitis and edema within the fragmented bone, suggesting the development of heterotopic ossification (HO). Diagnostic ultrasound revealed signs of IFI, not evident on MRI. Ultrasound-guided corticosteroid injection in her ischial bursa and ischiofemoral space provided complete relief. The patient was able to resume her activities of daily living and sports-related activities without pain. Although interventional treatments may provide temporary pain relief, a multimodal approach is required for the treatment of HO.

Skeletal and dental age estimation via postmortem computed tomography in Polish subadults group

This article is a retrospective analysis of postmortem computed tomography scans of ossification stages of the anterior and posterior intra-occipital sutures, the anterior arch of the atlas, and the neurocentral junction of the axis. We also analyzed the development of secondary ossification centers in the proximal humeral, femoral, and tibial epiphyses, and the distal femoral and tibial epiphyses. Additionally, the development of primary ossification centers in the wrist and metacarpals, and maxillary and mandibular deciduous tooth maturation. A total of 58 cadavers (35 males, 23 females), whose age ranged from 3rd month of pregnancy to 14 years, were analyzed. The results of this study show that analysis of synchondrosis closure, primary, and secondary ossification center development and deciduous tooth changes are a good tool for age estimation in subadults group (fetuses, newborns, infants, and children). The results of the study in a Polish population are consistent with those reported by other authors.

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.

Acute Pelvic and Hip Apophyseal Avulsion Fractures in Adolescents: A Summary of 719 Cases

BACKGROUND

Apophyseal avulsion fractures of the pelvis and hip are common injuries in adolescent athletes. However, high volume comparative studies elucidating the spectrum of injuries are largely absent from the literature. The current study provides a comprehensive analysis of demographic, anatomic, pathophysiological, clinical, and athletic-related variables associated with such injuries in an extensive population of affected adolescents.

METHODS

A retrospective review was performed of records of patients presenting to a single tertiary care pediatric hospital between January 1, 2005, and July 31, 2020, collecting variables including patient sex, age, body mass index, fracture location, injury mechanism, sport at the time of injury, and duration of prodromal symptoms.

RESULTS

Seven hundred nineteen fractures were identified in 709 patients. The average patient age was 14.6, and 78% of the fractures occurred in male patients. The anterior inferior iliac spine (33.4%), anterior superior iliac spine (30.5%), and ischial tuberosity (19.4%) were the most common fracture sites. The most common injury mechanisms were running (27.8%), kicking (26.7%), and falls (8.8%). The most common sports at the time of injury were soccer (38.1%), football (11.2%), and baseball (10.5%). Fracture site was significantly associated with patient sex, age, body mass index, laterality, mechanism, sport, time from injury, and presence of prodromal symptoms. The annual volume of pelvic avulsion fractures treated at the institution increased significantly from n=17 in 2005 to n=75 in 2019.

CONCLUSIONS

Adolescent pelvic and hip avulsion fractures occur during a narrow window of age and skeletal maturation and are frequently sustained during sporting activities. Each fracture location is associated with certain demographic, mechanistic, and patient-specific characteristics. The associations between fracture site and patient-specific or injury-specific variables offer insights into the pathophysiology and possible underlying biomechanical risk factors that contribute to these injuries.

LEVEL OF EVIDENCE

This is a level III retrospective study.

Apophyseal Avulsion of the Rectus Femoris Tendon Origin in Adolescent Soccer Players

Apophyseal avulsions of the rectus femorus tendon (RFT) at the anterior inferior iliac spine (AIIS) can occur in adolescents, often while performing soccer. Patient-reported outcomes (PROMs) and time to return to sport of these patients are relatively unknown. Therefore, the aim of this study was to assess the PROMs and return to sports of patients with AIIS avulsions and compare the results with those reported in the literature. This is a case series of seven consecutive patients presenting at our hospital between 2018 and 2020 with an apophyseal avulsion of the RFT from the AIIS. The patients were assessed with use of the WOMAC and Tegner scores and return to sports was evaluated. All patients were male soccer players (median age 13 years; range, 12–17). They were all initially treated non-operatively. One of the patients subsequently needed excision surgery of a heterotopic ossification because of non-transient hip impingement. All other patients recovered after a period of relative rest. Median time to return to sports was 2.5 months (range, 2–3). At a median follow-up of 33 months (range, 18–45), the WOMAC (median, 100; range, 91–100) and Tegner scores (median, 9; range, 5–9) were high. In accordance with the existing literature, most patients with apophyseal avulsions of the AIIS recover well with non-operative treatment. However, the avulsion can lead to hip impingement due to heterotopic ossifications possibly needing surgical excision. Sport resumption is achievable after 2–3 months, and patient-reported outcomes are highly satisfactory in the long term.

Relative skeletal maturity status affects injury burden in U14 elite academy football players

Maturation progresses at different times and at different rates between individuals. Thus, differences in maturity status exist among players in the same chronological age-based category, especially in U14 players. The purpose of this prospective study was to describe injury burden according to the relative skeletal maturity status in U14 elite academy football players. From 2011 to 2020 injuries and individual exposure (training and match) were prospectively recorded in 183 male U14 players. Skeletal age (SA) was assessed using the Tanner-Whitehouse 2 method. Relative skeletal maturity status [SA minus chronological age (CA)] was classified as follows: early (SA-CA > 0.5), on-time (SA-CA ± 0.5) and late (SA-CA < -0.5). Overall and specific injury burden (days lost/1000h) and rate ratios for comparisons between groups were calculated. Overall injury burden was 2.8-times higher (3.6-times in training) in early maturers compared with late maturers. Growth-related injuries were the most burdensome injuries in all three groups, but significant differences were not found between groups. Muscle injuries were 4-times more burdensome in early maturers compared with on-time and late maturers. Besides, joint/ligament injuries were 7- and 12- times less burdensome in late maturers than in on-time and late maturers, respectively. Significant differences between groups in overall and specific injury burden were not found in matches. Our results showed different injury patterns in U14 early, on-time and late maturers. Hence, monitoring maturity seems crucial to detect potential injuries that cause the greatest disruption, and facilitate design of targeted injury prevention programs.

Pediatric and Adolescent Fractures of the Acetabulum Treated With ORIF: What Are Their Functional Outcomes?

OBJECTIVES

To evaluate the functional outcomes of pediatric and adolescent patients (<18 year old) who sustained acetabulum fractures that were treated with open reduction internal fixation (ORIF).

DESIGN

Retrospective cohort.

SETTING

Level 1 trauma center.

PATIENTS

Thirty-four pediatric and adolescent patients underwent acetabulum fracture ORIF between 2001 and 2018. Of the operatively treated patients, 21 patients had sufficient follow-up (>6 months), one died after fixation secondary to other traumatic injuries, and 12 patients were lost to follow-up.

INTERVENTION

Acetabulum fracture ORIF.

MAIN OUTCOME MEASUREMENT

The SF-36 Health Survey and Short Musculoskeletal Functional Assessment (SMFA) were compared with population norms. The modified Merle d'Aubigné clinical hip score, Matta radiologic outcome, and postoperative complications were also documented.

RESULTS

Functional outcome data were available at a mean of 5 years 2 months. Mean SF-36 scores were 44.8 and 50.1 for the physical component score and mental component scores, respectively, which did not differ significantly from US population norms (physical component score mean: 50, P = 0.061 and mental component score mean: 50, P = 0.973). Furthermore, the mean SMFA Bother Index score was 18.6, which is not significantly different from the population norm mean of 13.8 (P = 0.268). However, the function index mean was 31.9, which was significantly worse than the population norm mean of 12.7 (P = 0.001). Two patients with a delayed reduction (>6 hours) of an acetabulum fracture dislocation had poor outcomes related to the development of avascular necrosis and post-traumatic osteoarthritis.

CONCLUSION

In this small cohort, 86% (18/21) of these patients had a favorable functional outcome with the exception of the SMFA Functional Index that was significantly less than population norms. Although long-term follow-up is needed, we advocate for operative management of pediatric and adolescent acetabulum fractures when adult displacement and instability criteria are present.

LEVEL OF EVIDENCE

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

Pelvic Region Avulsion Fractures in Adolescent Athletes: A Series of 242 Cases

OBJECTIVE

The objective of this descriptive study was to evaluate pelvic region avulsion fractures in adolescents, including age of injury, location of injury, activity and mechanism at time of injury, treatments used, duration of treatment, and outcomes.

DESIGN

This was a retrospective chart review of patients who presented with pelvic region avulsion fracture over a 19-year period.

SETTING

Private practice, primary care sports medicine clinic.

PATIENTS

All patients younger than 20 years of age diagnosed with an acute pelvic region avulsion fracture.

INTERVENTIONS

There was no set intervention protocol. A variety of interventions and combination of interventions were used and determined by the treating physician on a case-by-case basis.

MAIN OUTCOME MEASURES

Clearance for return toward sport activities.

RESULTS

Of the 242 cases, 162 were male. Soccer was the most common sport at the time of injury, and running/sprinting was the most common mechanism. Males were generally older at presentation and were more likely than females to have anterior inferior iliac spine injuries, whereas females were more likely to have iliac crest avulsions. Conservative treatment was effective in all cases. Males were treated for a shorter duration than females, but this difference was not statistically significant.

CONCLUSIONS

Pelvic avulsion fractures are a rare injury in adolescent athletes. Males are twice as likely to experience these injuries and are older at presentation compared to females. Conservative management leads to successful outcomes in most cases.

Sequential Epiphyseal Cartilage Changes of Femoral Heads in C57BL/6 Female Mice Treated with Excessive Glucocorticoids

OBJECTIVE

Excessive use of glucocorticoids (GCs) may cause adverse effects on the skeletal system in children. However, only a few studies have reported the effects of GCs on the epiphyseal cartilage. This study aimed to uncover the subsequent epiphyseal cartilage changes of immature femoral heads after excessive GC treatment in a mouse model and explain the pathological changes preliminarily.

DESIGN

Female C57BL/6 mice were divided into control and model (excessive GC treatment) groups. The structure of the femoral heads was evaluated by using micro-computed tomography, hematoxylin-eosin staining, and safranin staining analyses. Immunohistochemistry was used to detect angiogenesis and cartilage metabolism. Western blotting and TUNEL staining were used to examine epiphyseal cartilage chondrocyte apoptosis. Primary chondrocytes were isolated from the femoral heads of healthy mice for in vitro studies. The effects of GCs on chondrocyte apoptosis and metabolism were determined by flow cytometry and Western blotting.

RESULTS

The epiphyseal cartilage ossification had started at 4 weeks posttreatment in a portion of mice; the ossification presented as a sequential process in the model group, while the epiphyseal cartilage maintained an unossified state in the control group. Vascular invasion into the epiphyseal cartilage of the model mice was observed at 4 weeks posttreatment. GCs induced chondrocyte apoptosis and altered chondrocyte metabolism in the epiphyseal cartilage.

CONCLUSIONS

The epiphyseal cartilage ossification accelerated in the femoral heads of female C57BL/6 mice after excessive GC treatment. Increased chondrocyte apoptosis, altered chondrocyte metabolism, as well as increased vascular invasion, are the potential factors influencing epiphyseal cartilage ossification.

How low can we go? A skeletal maturity threshold for probabilistic visual sex estimation from immature human os coxae

OBJECTIVES

The appearance of sexually dimorphic traits varies depending on the type of bone, age, environmental and genetic factors and is closely linked to skeletal maturation sequence. Subadult sex estimation currently shows inconsistent accuracy and methods do not incorporate indicators of maturation. The goal of this study is to apply the Santos et al. (2019) adult sex estimation method on virtually reconstructed subadult os coxae and account for pelvic maturation.

MATERIAL AND METHODS

The right os coxae of 194 female and male individuals aged 11-30 years from Marseille, France were virtually reconstructed from computed tomography (CT) scans. Santos et al.'s (2019) 11 traits were scored as female, male, or indeterminate. Maturation of 10 pelvic epiphyseal sites was scored using a four-stage system (0-3) to obtain a composite maturity score from 1 to 30.

RESULTS

Three maturity groups were identified based on composite maturity scores ranging from 0 to 30. Individuals with a composite maturity score of 15 or higher showed 98 % sex estimation accuracy and a 6 % indeterminate rate. Scores of 2 for the ischiatic tuberosity or 1 for the anterior superior iliac spine can be used as proxies for a composite maturity score of 15 and application on incomplete bones.

DISCUSSION

Sexual dimorphism was observed in the epiphyseal maturation sequence and the development of sexually dimorphic pelvic traits. The Santos et al. (2019) method is applicable on immature individuals who meet a maturation threshold with comparable accuracy to adults, without relying on known or estimated age.

Pelvic Avulsion Injuries in the Adolescent Athlete

Pelvic avulsion fractures are common in youth athletes; many of these injuries can be treated conservatively. This article reviews the etiology, presentation, and management of the more common pelvic avulsion fractures, including anterior superior iliac spine, anterior inferior iliac spine, ischial tuberosity, and iliac crest avulsions. Adolescent pelvic avulsion fractures rely on the amount of fracture displacement to guide treatment. Conservative management includes rest and avoiding use of the muscle(s) that attach to the avulsed fragment. Operative treatment is reserved for widely displaced fractures or symptomatic nonunions. With appropriate treatment, young athletes frequently return to their same level of sport.

Lack of Abdominal Stability and Control as a Possible Contributor to Rectus Femoris Avulsion Fracture in the Adolescent Soccer Player: A Case Report

PURPOSE

To describe evaluation and physical therapy treatment for an athlete who is male and 13 years old with healing bilateral rectus femoris avulsion fractures.

SUMMARY OF KEY POINTS

Fractures of the anterior inferior iliac spine may be linked to poor abdominal stability in soccer athletes who are male and an adolescent. The development and use of an abdominal stability screening tool could be an efficient and effective way to determine fracture risk and guide prevention programs.

CONCLUSIONS AND RECOMMENDATIONS FOR CLINICAL PRACTICE

Following 8 weeks of conservative physical therapy treatment, the athlete met all goals and returned to pain-free soccer activities without residual impairments. Four months following discharge, he reported full participation in soccer competition without complications. This case illustrates that abdominal weakness is a potential risk factor for anterior inferior iliac spine avulsion fracture. Screening for abdominal weakness and incorporating preventative programs into training regimens is recommended to prevent anterior inferior iliac spine injuries in this population.

High-Energy Fractures of the Pelvis and Acetabulum in Pediatric Patients

Fractures of the pelvis and acetabulum, although uncommon in the pediatric cohort, represent a range of injuries with similarities to those seen in the adult cohort but with key differences that are important for the treating physician to be aware of to allow for systematic evaluation and management of these potentially life-threatening injuries. As the pediatric skeleton matures, changes in anatomy and physiology influence injury pattern, diagnosis, treatment, and complications. High-energy fractures of the pediatric pelvis are particularly concerning given the reported mortality rates ranging from 3.2% to 18%, with severe fracture patterns being associated with visceral injury in up to 60% of patients. The unique complexity of pediatric patients requires a multidisciplinary team to fully address their care. A systematic approach to the initial evaluation and diagnosis of pediatric patients with fractures of the acetabulum or pelvic ring aids in choosing between surgical and nonsurgical management of these fractures and avoiding complications unique to the maturing skeleton. We present such an approach to assist the practitioner who infrequently treats these uncommon injuries.

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).

Activation of β-catenin in Col2-expressing chondrocytes leads to osteoarthritis-like defects in hip joint

Although osteoarthritis (OA) in the hip joint is a common and debilitating degenerative disease, the precise molecular mechanisms underlying its pathological process remains unclear. This study sets out to investigate whether β-catenin plays a critical role in hip OA pathogenesis. Here, we showed overexpressed β-catenin protein in human OA cartilage tissues. Then, we analyzed β-cat(ex3)^Col2ER mice, in which β-catenin gene was conditionally activated in femoral head chondrocytes. At 2 months of age, β-cat(ex3)^Col2ER mice already showed a phenotype of severe cartilage degeneration in the femoral head. More changes observed in β-cat(ex3)^Col2ER mice with age included subchondral sclerosis and osteophyte formation along joint margins, resembling a hip OA phenotype in humans. In addition, cartilage degradation and chondrocyte apoptosis as the results of β-catenin activation possibly contributed to this hip OA-like phenotype. Overall our findings provide direct evidence about the importance of β-catenin in hip OA pathogenesis.