Ossification center of the infant hip: sonographic and radiographic correlation

Imaging of Disease and Normal Variant Patterns in Pediatric Hips

The pediatric hip undergoes significant changes from infancy through adolescence. Proper maturation is crucial for the development of a stable and functional hip joint. Imaging interpretation of the pediatric hip requires distinguishing normal variants and maturation patterns from pathology. We review femoral ossification centers, variants, and conditions that affect the proximal femur, such as Legg-Calvé-Perthes disease; the acetabulum, such as developmental hip dysplasia; the acetabular labrum, such as femoroacetabular impingement; and synovial pathology in children through adolescence. Understanding the spectrum of hip conditions and using advanced imaging techniques are essential for the accurate diagnosis and effective management of pediatric hip disorders.

Imaging of developmental dysplasia of the hip: ultrasound, radiography and magnetic resonance imaging

Developmental dysplasia of the hip (DDH) describes a broad spectrum of developmental abnormalities of the hip joint that are traditionally diagnosed during infancy. Because the development of the hip joint is a dynamic process, optimal treatment depends not only on the severity of the dysplasia, but also on the age of the child. Various imaging modalities are routinely used to confirm suspected diagnosis, to assess severity, and to monitor treatment response. For infants younger than 4 months, screening hip ultrasound (US) is recommended only for those with risk factors, equivocal or positive exam findings, whereas for infants older than 4-6 months, pelvis radiography is preferred. Following surgical hip reduction, magnetic resonance (MR) imaging is preferred over computed tomography (CT) because MR can not only confirm concentric hip joint reduction, but also identify the presence of soft-tissue barriers to reduction and any unexpected postoperative complications. The routine use of contrast-enhanced MR remains controversial because of the relative paucity of well-powered and validated literature. The main objectives of this article are to review the normal and abnormal developmental anatomy of the hip joint, to discuss the rationale behind the current recommendations on the most appropriate selection of imaging modalities for screening and diagnosis, and to review routine and uncommon findings that can be identified on post-reduction MR, using an evidence-based approach. A basic understanding of the physiology and the pathophysiology can help ensure the selection of optimal imaging modality and reduce equivocal diagnoses that can lead to unnecessary treatment.

Patchy increased echogenicity: a sonographic sign of femoral head necrosis following reduction and casting for developmental dysplasia of the hip

A developmental dysplasia of the hip (DDH) case treated by closed reduction and casting and subsequently confirmed to have avascular necrosis (AVN) was retrospectively noted to have an abnormal pattern of echogenicity in the femoral head on sonograms obtained within 1.5 months of surgery. Patchy increased echogenicity in parts of the unossified cartilage replaced the normal pattern of central coalescence of vessels described with development of the ossification center. An additional case with similar findings confirms this should be considered a sign of evolving AVN following closed reduction.

Changes in femoral head size and growth rate in young children with severe developmental dysplasia of the hip

BACKGROUND

Developmental dysplasia of the hip (DDH) is known to result in smaller femoral head size in toddlers; however, alterations in femoral head size and growth have not been documented in infants.

OBJECTIVE

To determine with ultrasound (US) whether femoral head size and growth are altered in infants (younger than 1 year of age) with severe DDH.

MATERIALS AND METHODS

We identified all patients at our tertiary care children's hospital from 2002 to 2014 who underwent US for DDH. We included studies with at least one hip with severe DDH, defined as <25% coverage of the femoral head, and excluded teratological DDH. We constructed a control group of randomized patients with normal US studies. Two pediatric radiologists blinded to diagnosis measured bilateral femoral head diameter. Inter-reader variability and femoral head diameter difference between dislocated and contralateral normal femoral heads were evaluated. Mean femoral head diameters were compared across types of hip joint; femoral head growth rates per month were calculated.

RESULTS

Thirty-seven children with DDH (28 female) were identified (median age: 33 days). The control group contained 75 children (47 female) with a median age of 47 days. Fifty-three of the 74 hips in the study group had severe DDH. Twenty-four children with DDH had completely dislocated hips (nine bilateral, five with contralateral severe subluxations). Thirteen other children had severe subluxation, two bilaterally. There was good inter-reader agreement in the normal femoral head group and moderate agreement in the severe DDH group. In the study group, severe DDH femoral head diameter was significantly smaller than their contralateral normal hip. Severe DDH femoral head diameter was significantly smaller than normal femoral head diameter in the control group. The severe DDH femoral head growth rate was slightly less but not significantly slower than normal femoral head growth rate in the study group.

CONCLUSION

On US during infancy, femoral head size is significantly reduced in severe cases of DDH.

Presence of the Ossific Nucleus and Risk of Osteonecrosis in the Treatment of Developmental Dysplasia of the Hip: A Meta-Analysis of Cohort and Case-Control Studies

BACKGROUND

Concern for increased risk of osteonecrosis in hips with an absent ossific nucleus has led some surgeons to delay reduction in the treatment of developmental dysplasia of the hip (DDH) until the ossific nucleus is present. A previous meta-analysis reported a potential protective effect against high-grade osteonecrosis (II to IV) when the ossific nucleus was present. With a greater number of publications on this topic, revisiting this analysis is warranted. The aim of this meta-analysis was to systematically review and analyze the best clinical evidence regarding the association between the status of the ossific nucleus and development of osteonecrosis following the treatment of DDH.

METHODS

MEDLINE, Embase, and Cochrane databases were systematically searched for studies including the status of the ossific nucleus and rate of osteonecrosis after open and closed reductions for the treatment of DDH. Study characteristics and risk estimates were extracted. Study quality was assessed using the Newcastle-Ottawa Scale. Pooled effect estimates were calculated using a random-effect model. Meta-regression assessed the relationships of reduction method, study quality, mean age at reduction, surgical approach, method of ossific nucleus assessment, and duration of follow-up to the odds of osteonecrosis.

RESULTS

In the 21 observational studies (18 retrospective, 3 prospective) that were included, osteonecrosis developed in 20.4% of the hips in which the ossific nucleus was present at reduction compared with 21.2% of the hips in which the ossific nucleus was absent. Presence of the ossific nucleus was not associated with decreased odds of any grade of osteonecrosis (odds ratio [OR] = 0.70, 95% confidence interval [CI] = 0.43 to 1.12) or of more severe osteonecrosis of Grades II to IV (OR = 0.70, 95% CI = 0.30 to 1.17). Meta-regression did not show any effect of the mean age at reduction, reduction method, surgical approach, study quality, minimum or mean duration of follow-up, method of ossific nucleus imaging, or osteonecrosis classification system on the relationship between presence of the ossific nucleus and the risk of osteonecrosis.

CONCLUSIONS

The current literature does not support the hypothesis that presence of the ossific nucleus at reduction is associated with lower risk of osteonecrosis. Prospective studies with long-term follow-up and blinded assessors are warranted to optimally evaluate the relationship between potential risk factors and the development of osteonecrosis.

LEVEL OF EVIDENCE

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

Quantitative anatomy of the primary ossification center of the femoral shaft in human fetuses

Purpose

Early clinical distinction of congenital defects in the femur is extremely important, as it determines the prognosis of the development of the lower limb. This study was performed to quantitatively examine the primary center of ossification in the femoral shaft with respect to its linear, planar, and volumetric parameters.

Materials and methods

Using methods of CT, digital-image analysis, and statistics, the size of the primary ossification center of the femoral shaft in 47 spontaneously aborted human fetuses aged 17–30 weeks was studied.

Results

With no sex and laterality differences, the best fit growth dynamics for femoral shaft ossification center was modelled by the following functions: y = 5.717 + 0.040 × (age)² ± 2.905 (R² = 0.86) for its length, y = −3.579 + 0.368 × age ± 0.529 (R² = 0.88) for its proximal transverse diameter, y = −1.105 + 0.187 × age ± 0.309 (R² = 0.84) for its middle transverse diameter, y = −2.321 + 0.323 × age ± 0.558 (R² = 0.83) for its distal transverse diameter, y = −50.306 + 0.308 × (age)² ± 18.289 (R² = 0.90) for its projection surface area, and y = −91.458 + 0.390 × (age)³ ± 92.146 (R² = 0.88) for its volume.

Conclusions

The size of the femoral shaft ossification center displays neither sex nor laterality differences. The ossification center in the femoral shaft follows quadratic functions with respect to its length and projection surface area, linear functions with respect to its proximal, middle, and distal transverse diameters, and a cubic function with respect to its volume. The obtained morphometric data of the femoral shaft ossification center are considered normative for respective prenatal weeks and may be of relevance in both the estimation of fetal ages and the ultrasound diagnostics of congenital defects.

Association between the ossific nucleus and osteonecrosis in treating developmental dysplasia of the Hip: updated meta-analysis

Background

A meta-analysis concluded that there was no effect of the femoral head ossification and the incidence of osteonecrosis in the treatment of developmental dysplasia of the hip (DDH), unless only osteonecrosis grades II-IV were considered. The meta-analysis, limited due to the small number of studies available at that time, identified a need for an update as further research emerges. We observed a trend in recent years towards delaying treatment of DDH in the absence of an ossified nucleus. Numerous new publications on this topic encouraged us to update the 2009 meta-analysis.

Methods

We performed a systematic review of the literature from 1967 to 2016 and included studies that reported on the treatment of DDH, the ossific nucleus and osteonecrosis. Two independent reviewers evaluated all articles. We performed a meta-analysis with the main outcome defined as the development of osteonecrosis of the femoral head at least two years after closed or open reduction.

Results

Of four prospective and ten retrospective studies included in the systematic review, 11 studies (1,021 hips) met the inclusion criteria for the meta-analysis. There was no significant effect of the ossific nucleus on the development of all grades of osteonecrosis (relative risk, 0.88; 95% confidence interval, 0.56–1.41) or osteonecrosis grades II–IV (0.67; 0.41–1.08). In closed reductions, the ossific nucleus halved the risk for developing osteonecrosis grades II–IV (0.50; 0.26–0.94).

Conclusions

Based on current evidence there does not appear to be a protective effect of the ossific nucleus on the development of osteonecrosis. In contrast to the previous meta-analysis, this update demonstrates that this remains the case irrespective of the grade of osteonecrosis considered relevant. This updated meta-analysis is based on twice as many studies with a higher quality of evidence.

Electronic supplementary material

The online version of this article (doi:10.1186/s12891-017-1468-6) contains supplementary material, which is available to authorized users.

Treatment and prevention of hip dysplasia in infants and young children

The diagnosis and treatment of developmental dysplasia of the hip in the infant are uniform, with consensus that diagnostic ultrasound and Pavlik harness management are standard procedures. Sequential procedures for failed early treatment, residual dysplasia and late diagnosis are dependent on the age and the severity of the dysplasia. This paper reviews the treatment of developmental dysplasia of the hip from birth to subsequent follow-up procedures, with particular reference to some of the senior authors' research and the Southampton approach to the management of hip dysplasia.

Correlation between avascular necrosis and the presence of the ossific nucleus when treating developmental dysplasia of the hip

PURPOSE

This study assessed whether avascular necrosis (AVN) is correlated with the presence or absence of the ossific nucleus (ON) at the initiation of conservative treatment for developmental dysplasia of the hip (DDH). To date, the correlation between the presence of the ON and AVN manifestations remains ambiguous.

METHODS

The medical records of 148 patients with 234 dislocated hips who presented at our institution between January 2006 and December 2007 were reviewed. Based on ultrasound examination, the hips were classified according to Graf IIIa, IIIb, and IV criteria. Patients aged >6 months were simultaneously examined by standardized pelvis radiography.

RESULTS

The ON was present in 84 hips (35.9 %) at the beginning of treatment. Treatment was begun at a mean age of 5 months, with overhead traction for 2 weeks followed by arthrography and a spica cast for 4 weeks. Afterwards, we used a Tübingen hip-flexion splint. The mean age at final follow-up was 87 months. Hips were radiographically evaluated at last follow-up according to the Ogden-Bucholz AVN classification scheme. There was no significant difference in AVN prevalence between ON(-) versus ON(+) hips in children aged ≤10 months (P = 0.681), whereas when all age groups were analyzed together, AVN was significantly increased in ON(+) hips (P = 0.002). Clinical examination revealed no differences in limping, leg length inequality, and range of motion of hips in the ON(-) versus ON(+) groups.

CONCLUSION

We conclude that DDH treatment should be performed early without regard to the presence or absence of the ON. Reduction should not be delayed beyond >10 months of age because any delay in treatment increases the incidence of AVN.

Precocious appearance of the capital femoral ossific nucleus in Larsen syndrome

BACKGROUND

Larsen syndrome is associated with multiple complications, including spinal deformities and recalcitrant joint dislocations. We noted capital femoral ossific nuclei on ultrasonographic images that were made for two infants with Larsen syndrome who were less than two weeks of age. We sought to confirm that this finding is common in patients with Larsen syndrome and unusual in patients with normal hips or idiopathic developmental dysplasia of the hip.

METHODS

We identified eight patients with Larsen syndrome who had undergone ultrasonographic or radiographic evaluation of the hips before the age of three months. We compared the findings for these eight patients with those for forty consecutive patients from a prospective study of infants with developmental dysplasia of the hip who had ultrasonographic evaluation of the hips at approximately three months of age, including twenty patients who had normal clinical and ultrasonographic findings and twenty who had clinical instability of one or both hips.

RESULTS

All eight patients with Larsen syndrome had radiographic or ultrasonographic evidence of an ossific nucleus at an average age of forty days (range, six to 115 days); four of these patients had evidence of an ossific nucleus at six to ten days of age. In comparison, only two of twenty normal infants (three of forty hips) and one of twenty infants (two of forty hips) with developmental dysplasia of the hip had ultrasonographic evidence of an ossific nucleus at an average age of eighty-four days (range, seventy-six to ninety-four days) (p < 0.0001, Fisher exact test).

CONCLUSIONS

In this small group of patients with clinically documented Larsen syndrome, the capital femoral ossific nucleus was evident on ultrasonography of the hip as early as six days of age and was unusual in normal patients or those with idiopathic developmental dysplasia of the hip. The detection of precocious development of a capital femoral ossific nucleus in infants being screened for skeletal anomalies may warrant further evaluation for the possibility of the presence of Larsen syndrome.

Phenotypic diversity in chondromyxoid fibroma reveals differentiation pattern of tumor mimicking fetal cartilage canals development: an immunohistochemical study

Chondromyxoid fibroma represents a rare benign cartilaginous tumor of young patients occurring in a subcortical metaphyseal location. The histogenesis of chondromyxoid fibroma has not yet been postulated, even though the conventional histology and recent immunohistochemical studies on phenotype of the mesenchymal cells and extracellular matrix components suggested its origin in immature cartilage. Therefore, we wished to compare the morphological pattern of immature cartilage tissue with chondromyxoid fibroma to investigate a possible developmental counterpart of chondromyxoid fibroma. Archival paraffin-embedded tissues from 4 fetal femora and 10 cases of chondromyxoid fibroma were analyzed simultaneously using histochemistry (safranin O) and established immunohistochemical antibodies (CD34, CD163, and smooth muscle actin). Vascularized cartilage canals growing into the fetal cartilage from the perichondrium displayed characteristic glomeruloid structures with central arterioles within the immature mesenchymal stroma and numerous superficial sinusoidal blood vessels accompanied by macrophage infiltration. Similarly, each case of chondromyxoid fibroma demonstrated admixture of two characteristic components: immature fibrous tissue of vascularized stroma with accumulation of macrophages in areas of superficial sinusoidal proliferation, and variable amounts of lobulated chondroid tissue. Based on the observed substantial morphological similarity between the cartilage canals and chondromyxoid fibroma, we suggest that the chondromyxoid fibroma represents a neoplasm originating from or mimicking the fetal cartilage canals within the immature cartilage.

The effect of the femoral head ossific nucleus in the treatment of developmental dysplasia of the hip. A meta-analysis

BACKGROUND

The role of the presence of the femoral head ossific nucleus as a risk factor for the development of osteonecrosis of the femoral head in infants with developmental dysplasia of the hip has been investigated in several small studies, but the results have been inconsistent. The purpose of the present study was to determine the effect of the presence of the ossific nucleus on the development of osteonecrosis.

METHODS

A systematic review of the medical literature from 1966 to 2007 was performed. Two independent reviewers evaluated all articles. Interrater agreement was determined, and the quality of evidence was evaluated. A meta-analysis was then performed with the main outcome defined as the development of osteonecrosis of the femoral head two years after reduction.

RESULTS

Six observational studies (five retrospective and one prospective) met the inclusion criteria. Inconsistency was found in that half of the studies demonstrated a protective effect of the ossific nucleus on the development of osteonecrosis whereas half of the studies did not. A meta-analysis (including 358 patients) showed no significant effect of the presence of the ossific nucleus on the development of grades-I through IV osteonecrosis, with forty-one cases of osteonecrosis (19%) found in infants in whom the ossific nucleus had been present at the time of hip reduction compared with thirty cases (22%) in the group without an ossific nucleus (relative risk=0.75, 95% confidence interval=0.46 to 1.21). When only radiographic changes of grade II or worse were considered to represent osteonecrosis, a significant difference in the prevalence of osteonecrosis was found, with fourteen cases of osteonecrosis (7%) in infants with an ossific nucleus compared with eighteen cases (16%) in those without an ossific nucleus (relative risk=0.43, 95% confidence interval=0.20 to 0.90). A subgroup analysis showed that the presence of the ossific nucleus reduced the probability of osteonecrosis by 60% (relative risk=0.41, 95% confidence interval=0.18 to 0.91) after closed reduction, but no significant effect was found in patients treated with open reduction (relative risk=1.14, 95% confidence interval=0.62 to 2.07). All studies demonstrated methodological weaknesses compromising the quality of evidence.

CONCLUSIONS

We did not find that the presence of the ossific nucleus had a significant effect on the development of osteonecrosis of any grade after hip reduction in infants with developmental dysplasia of the hip. The meta-analysis suggested that the presence of the ossific nucleus has a protective effect against the development of the more severe forms of femoral head osteonecrosis. However, the quality of evidence is moderate, and additional research is likely to have an important impact on the confidence in the estimate of the effect and may change this estimate.

Developmental dysplasia of the hip

In its severest form, developmental dysplasia of the hip is one of the most common congenital malformations. The pathophysiology and natural history of the range of morphological and clinical disorders that constitute developmental dysplasia of the hip are poorly understood. Neonatal screening programmes, based on clinical screening examinations, have been established for more than 40 years but their effectiveness remains controversial. Whereas systematic sonographic imaging of newborn and young infants has afforded insights into normal and abnormal hip development in early life, we do not clearly understand the longer-term outcomes of developmental hip dysplasia, its contribution to premature degenerative hip disorders in adult life, and the benefits and harms of newborn screening. High quality studies of the adult outcomes of developmental hip dysplasia and the childhood origins of early degenerative hip disease are needed, as are randomised trials to assess the effectiveness and safety of neonatal screening and early treatment.

Sonography of hip dysplasia

Early diagnosis of developmental dysplasia of the hip (DDH) is important to institute appropriate treatment and reduce the incidence of long-term complications. Risk factors for DDH include genetic, developmental, mechanical, and physiologic factors. Physical examination using Ortolani and Barlow maneuvers is standard for early detection. Plain film radiography is limited for the diagnosis of DDH even when applying several classic landmarks, lines, and measurements, due to the lack of visualization of the cartilaginous components of the infant's hip. Ultrasound arose as a tool for evaluation of the cartilaginous structures of the hip in the early 1980s. Graf's method of examination by ultrasound stresses morphology, whereas dynamic examination uses physical maneuvers to elicit laxity of the hip. The Pavlik harness is the mainstay of treatment of DDH in the young infant, and ultrasound examination in the harness is useful to monitor progress. Closed or open surgical reduction is reserved for unresponsive or advanced cases. Universal ultrasound screening of newborns is not deemed cost effective by most North American authors, although in Europe non-selective screening has been more widely used.

Avascular necrosis after treatment of DDH: the protective influence of the ossific nucleus

We retrospectively reviewed the results of open or closed reduction for developmental dysplasia of the hip (DDH) in 49 children younger than 12 months old, who had 57 hip dislocations. Group A (18 hips) developed partial or complete avascular necrosis (AVN), and group B (39 hips) did not develop AVN. Thirty-eight hips were treated by closed reduction, and 17 had open reduction. One patient with bilateral hip dislocation initially had closed reductions followed by bilateral open reduction 3 months later. With the numbers available for study, there was no significant difference in the occurrence of AVN with respect to variables such as preliminary traction, closed versus open reduction, Pavlik harness use, and age at the time of operative intervention. However, the presence of the ossific nucleus before reduction, detected either by radiographs (p < 0.001) or ultrasonography (p = 0.033) was statistically significant in predicting AVN. Only one (4%) of 25 hips with an ossific nucleus developed AVN, whereas 17 (53%) of 32 hips without an ossific nucleus before reduction developed AVN. Our results suggest that the presence of the ossific nucleus before closed or open reduction for DDH may decrease the risk of AVN.

Assessment of congenital hip dislocation with real-time ultrasound: a pictorial essay

Real-time ultrasound (US) is the imaging method of choice for diagnosis and follow-up of congenital dislocation of the infant hip (CDH). Clinical aspects and the role of imaging are reviewed. Technique and anatomy, both normal and abnormal, are illustrated, as well as, the use of sonography during treatment with Pavlik harness and spica cast. Correlation of ultrasound findings with clinical examination, other available imaging studies and long-term patient follow-up shows 100% sensitivity and 100% specificity for real-time US diagnosis of CDH.

Sonographic guidance for infant hip reduction under anesthesia

An initial attempt to reduce a hip dislocation in a 15-month-old by palpation under general anesthesia led to the subsequent discovery of a posterior subluxation by CT. During the second attempt, sonographic guidance in the operating room was used to show concentric reduction both before and after the application of a spica cast. Successful reduction was later confirmed by CT. Imaging by real-time sonography can be useful in monitoring infant hip reduction.