Stressed or fractured: MRI differentiating indicators of physeal injury.

OBJECTIVE: To identify MRI findings that can indicate chronic physeal stress injury and differentiate it from acute Salter-Harris (SH) fracture of the pediatric knee or wrist. METHODS: IRB-approved retrospective study of consecutively selected knee and wrist MRIs from 32 athletes with chronic physeal stress injury and 30 children with acute SH fracture. MRI characteristics (physeal patency, physeal thickening, physeal signal intensity (SI), continuity of the zone of provisional calcification (ZPC), integrity of the periosteum and/or perichondrium, pattern of periphyseal and soft tissue edema signal, and joint effusion) were compared. RESULTS: Forty-eight chronic physeal stress injuries (mean age 13.1 years [8.2-17.5 years]) and 35 SH fractures (mean age 13.3 years [5.1-16.0 years]) were included. Any physeal thickening was more common with chronic stress injury (98% vs 77%, p = 0.003). Abnormal physeal SI was more common with SH fractures (91% vs 67%, p = 0.008). ZPC discontinuity strongly suggested chronic stress injury (79% vs 49%, p < 0.004). Periosteal and/or perichondrial elevation or rupture and soft tissue edema characterized most of the acute SH fractures (p < 0.001) and were seen only in 1 chronic stress injury (< 2%). While periphyseal edema was not significantly different in the two groups (p = 0.890), a joint effusion was associated with acute SH fracture (p < 0.001). CONCLUSION: Chronic physeal stress injury of the pediatric knee and wrist shows higher incidence of ZPC discontinuity and focal physeal thickening compared to SH fracture, reflecting disruption in normal endochondral ossification. However, these findings can overlap in the 2 groups. Periosteal and/or perichondrial injury, soft tissue edema signal, and joint effusion strongly suggest SH fracture and are rarely present with chronic stress injury.

Magnetic resonance imaging protocols for pediatric acute hematogenous osteomyelitis.

Pediatric musculoskeletal infection can be a challenging clinical diagnosis. MRI protocols should be tailored appropriately to diagnose and localize sites of infection, to determine alternative pathologies that could explain the child's presentation, and to identify complications that could alter treatment or lead to devastating consequences in growing bones. In this review, we discuss MRI protocols tailored for suspected acute appendicular musculoskeletal infection in children. These protocols are based on patient age in order to generally reflect the developmental stage of the child, the corresponding relevant anatomy and physiology, and the skeletal maturity-dependent physiopathology of musculoskeletal infections.

Physeal injuries of the clavicle: pediatric counterparts to adult acromioclavicular and sternoclavicular joint separations.

The epiphyses at the medial and lateral ends of the clavicle are small, ossify relatively late, and may not fuse until early adulthood. Because of this unique anatomy, pediatric and young adult injuries that involve the clavicle often differ from the patterns typically seen in older adults. Clavicular trauma that affects the acromioclavicular joint laterally or sternoclavicular joint medially often results in a physeal fracture and as such, can go unrecognized or be mistaken for a joint dislocation. Radiographic assessment is challenging, particularly when the epiphysis is not yet ossified. However, MR imaging allows for visualization of the cartilage, periosteum and perichondrium, and ligaments of the affected joints. Lateral clavicle physeal injuries can be categorized by the Dameron and Rockwood system, the pediatric correlate to the Rockwood classification of adult acromioclavicular joint injuries. Medial clavicle physeal fractures, similar to adult sternoclavicular joint dislocations, may result in anterior or posterior displacement. Because of their great ability to heal and remodel, clavicular physeal fractures respond better to conservative management than true acromioclavicular or sternoclavicular joint dislocations. Therefore, it is essential to recognize the true nature of these injuries, as there are implications for successful treatment and appropriate prognosis.

Magnetic resonance imaging of medial collateral ligament avulsion fractures of the knee in children: a potentially underestimated injury.

BACKGROUND: Literature regarding medial collateral ligament (MCL) injuries is focused on adults with superficial MCL disruptions. However, children follow different injury patterns, with avulsion fractures at ligament attachment sites occurring commonly. Such avulsions have not been characterized for pediatric MCL injuries. OBJECTIVE: To elucidate imaging findings, and review management and outcomes of pediatric MCL avulsion fractures. MATERIALS AND METHODS: We conducted a 10-year retrospective review of knee magnetic resonance (MR) imaging reports for patients younger than 16 years old diagnosed with acute MCL avulsion fracture. MR imaging was reviewed to confirm and characterize the components of the avulsion (perichondrium without or with cartilage, and/or bone) and to identify additional knee injuries. Radiographs, if available, from the time of injury were reviewed. Clinical management and patient outcomes were recorded. RESULTS: Eighteen patients (13 boys, 5 girls) incurred an acute MCL avulsion fracture. All avulsions involved the deep MCL attachment: 17 meniscofemoral and 1 meniscotibial component. Two avulsions also included the superficial MCL attachment. Nine boys had non-osseous avulsions, all radiographically occult. All girls had radiographically apparent avulsions. Three girls and three boys sustained associated knee derangements, most commonly anterior cruciate ligament (ACL) injury (n=4). All MCL avulsions were initially treated conservatively; one child required subsequent surgery for ongoing pain. CONCLUSION: Pediatric MCL avulsion fractures in this study uniformly involve the attachment of the deep MCL and can be entirely non-osseous, particularly in boys who lag in skeletal maturity, making these injuries radiographically occult. MR imaging may be required to recognize these avulsions, which can impact the duration of rest and knee bracing.

Describing pediatric fractures in the era of ICD-10.

Childhood fractures are extremely common. The recent trend is to direct certain fracture care from orthopedic specialists to primary care clinicians. However, to confirm an appropriate level of treatment, the initial diagnosis must be accurate, the description precise, and the communication between those caring for the child consistent. This review illustrates descriptors used at one institution that are based on terminology consensually created between radiologists and orthopedic surgeons for common pediatric fracture types and their displacement, and that satisfy the expanded and detailed International Statistical Classification of Diseases and Related Health Problems (ICD)-10 requirements for successful coding.

It's time to recognize the perichondrium.

The perichondrium is a complex structure centered at the chondro-osseous junction of growing bones. It plays an important role in both normal skeletal development and in pathological conditions. This review illustrates the normal anatomy, function and imaging appearance of the perichondrium from fetal development to older childhood. The radiologic appearance of the perichondrium in skeletal trauma, infection and tumors in which it plays a role also are reviewed.

Correction to: It's time to recognize the perichondrium.

The originally published version of this article contained typesetting errors in Table 1 and the legend for Fig. 10. The correct versions of the table and figure legend are included below. The original article has been corrected.

Lower-extremity growth patterns and skeletal maturation in children with unilateral fibular hemimelia.

BACKGROUND: Fibular hemimelia is the most common congenital long-bone deficiency. It is usually unilateral and results in a limb-length discrepancy. The literature generally subscribes to the concept of constant inhibition, a process by which limb-length ratios between the shorter and longer extremity remain constant throughout growth, but scientific data supporting this concept are sparse. Additionally, recent literature suggests that these children have abnormal skeletal maturation. OBJECTIVE: To elucidate the lower-extremity long-bone growth patterns and skeletal maturation of children with unilateral fibular hemimelia. MATERIALS AND METHODS: We reviewed medical records of children with unilateral fibular hemimelia seen at a large pediatric hospital over a 17-year period. Inclusion criteria were: at least two scanograms prior to any shortening/lengthening procedure, and no other congenital or acquired disorders. We collected the study cohort's femoral and tibial lengths (scanogram reports), plotted them against patient chronological ages and compared them to published growth standards. When these children's bone ages (Greulich and Pyle) were available, we plotted them against the children's chronological ages. RESULTS: Twenty-three children were included (total=115 scanograms). At least 1 bone-age assessment was performed in 19 children (total=84 bone ages). All bone growth curves were within normal growth standards for the femur and tibia. Length ratios between shorter and longer limbs remained constant. Skeletal maturation was within two standard deviations of normal in 90% of bone ages. CONCLUSION: Lower-extremity long bones of children with unilateral fibular hemimelia have relatively normal growth curves, supporting and confirming the concept of constant inhibition. Most children show normal skeletal maturation.

Constant inhibition in congenital lower extremity shortening: does it begin in utero?

BACKGROUND: Limb-length discrepancy (LLD) in children with congenital lower extremity shortening is constant in proportion from birth to skeletal maturity (known as constant inhibition), but its developmental pattern in utero is unknown. The popular prenatal multiplier method to predict LLD at birth assumes constant inhibition in utero to be true. Verifying the in utero developmental pattern of LLD, and thus confirming the validity of the prenatal multiplier method, is crucial for meaningful prenatal parental counseling. OBJECTIVE: To elucidate the in utero developmental pattern of LLD in fetuses with congenital lower extremity shortening. MATERIALS AND METHODS: Clinical indications for 3,605 lower extremity radiographs performed on infants (<1 year old) at a large tertiary hospital over a 17-year period were reviewed. Inclusion criteria were (1) diagnosis of congenital lower extremity shortening, (2) bilateral lower limb postnatal radiographs documenting LLD and (3) fetal ultrasound (US) documenting LLD. Available measurements of femoral, tibial and fibular lengths on fetal US and postnatal radiographs were collected. Prenatal and postnatal length ratios of shorter-to-longer bones were calculated and compared. RESULTS: Eighteen infants met inclusion criteria. Diagnoses were proximal focal femoral deficiency=4, congenital short femur=2, tibial hemimelia=3, posteromedial tibial bowing=6 and fibular hemimelia=3. The correlations between postnatal and prenatal length ratios were high for the femur, tibia and fibula (R>0.98, P<0.0001). The relative differences in the postnatal and prenatal length ratios of these bones were small (|average|<0.026, standard deviation <0.068). CONCLUSION: Our data indicate that the postnatal and prenatal length ratios were equivalent, supporting the constant inhibition pattern of LLD in utero, thus validating the prenatal multiplier method for predicting LLD.

Hematogenous Osteomyelitis in Infants and Children: Imaging of a Changing Disease.

In children, hematogenous osteomyelitis is an infection that primarily affects the most vascularized regions of the growing skeleton. The disease has increased in frequency, virulence, and degree of soft-tissue involvement. The change in clinical manifestations and management over the past 2 decades should be reflected in the current imaging approach to the disease. Imaging of infection must depict the location of a single focus or of multiple foci of involvement and the presence of drainable collections. This review provides an overview of the imaging implications directed by the changing epidemiology, the newer insights of anatomy and pathophysiology, the imaging characteristics with emphasis on specific locations and disease complications, and the differential diagnosis considerations. In addition, basic imaging guidelines for appropriate extent of area to image based on patient age are provided. © RSNA, 2017.

The Effect of Scapular Position on Magnetic Resonance Imaging Measurements of Glenohumeral Dysplasia Caused by Neonatal Brachial Plexus Palsy.

PURPOSE: Neonatal brachial plexus palsy (NBPP) frequently causes glenohumeral dysplasia. Quantification of this dysplasia on magnetic resonance imaging can determine the need for and the success of nonsurgical or surgical intervention. However, we hypothesize that the variable position of the scapula on the thorax between affected and unaffected shoulders affects dysplasia measurements. METHODS: Magnetic resonance imaging studies were analyzed from 19 NBPP patients (ages 0.8-18 years; median, 2.4 years) without prior shoulder surgery. Three reviewers measured the glenoid version angle (GVA) and percentage of humeral head anterior to the midscapular line (PHHA) on standard axial images ("thoracic axial") and on reformatted axial images aligned perpendicular to the scapular plane ("scapular axial"), which corrects for scapulothoracic position. Scapular tilt and protraction were measured to assess their impact on the difference between thoracic and scapular GVA and PHHA measurements. Intra- and interrater reliability were calculated for GVA and PHHA on both views. RESULTS: The GVA of the affected shoulder was significantly greater on thoracic than on scapular images, by an average of 5° and as much as 34°. The PHHA was significantly less in the affected shoulders on thoracic than on scapular images, by an average of 5% and as much as 33% of humeral head width. The difference in GVA, but not PHHA, between thoracic and scapular axial images in the affected shoulder correlated with scapular tilt. Unaffected shoulders showed no significant difference in GVA or PHHA between thoracic and scapular axial images. Interrater reliability ranged from fair to substantial and did not differ between thoracic and scapular images. CONCLUSIONS: Thoracic axial images overestimate the severity of glenohumeral dysplasia in NBPP, owing at least in part to the variable position of the scapula on the thorax. This confounding effect must be considered in interpretation of axial quantitative measures of glenohumeral dysplasia in NBPP. TYPE OF STUDY/LEVEL OF EVIDENCE: Diagnostic III.

Imaging assessment of patellar instability and its treatment in children and adolescents.

Transient patellar dislocation is a common entity in children and adolescents, characterized by lateral dislocation of the patella, usually with spontaneous reduction. Many predisposing conditions have been described, including trochlear dysplasia, excessive lateral patellar tilt, patella alta and lateralization of the tibial tuberosity. Associated injuries are bone bruises of the patella and lateral femoral condyle, tears of the medial retinaculum that include the medial patellofemoral ligament (MPFL), tears of the vastus medialis obliquus muscle, injuries of articular cartilage, and intra-articular bodies. Children who are refractory to conservative management, have a large cartilage defect, or are at substantial risk for recurrent dislocations are candidates for surgical procedures to prevent future dislocations. Procedures can include MPFL repair or reconstruction, tibial tubercle repositioning and lateral retinacular release. The purpose of this review is to illustrate the imaging findings of transient patellar dislocation in the acute setting, the normal imaging appearance after surgical intervention, and post-surgical complications.

Development of the long bones in the hands and feet of children: radiographic and MR imaging correlation.

The long bones of the hands and feet in children have an epiphyseal end with a secondary center of ossification and an adjacent transverse physis. In contrast to other long bones in the body, the opposite end in the hands and feet, termed the non-epiphyseal end, is characterized by direct metaphyseal extension of bone to complete terminal ossification. The purpose of this pictorial essay is to illustrate the developmental stages of each end of the long bones of the hands and feet with radiographic and MR imaging to provide a foundation from which to differentiate normal from abnormal growth.

Childhood asymmetrical labium majus enlargement sonographic and MR imaging appearances.

BACKGROUND: Childhood asymmetrical labium majus enlargement (CALME) has been described sparsely in recent surgery, pathology, pediatric and gynecology literature; however, no comprehensive description from a radiology perspective has been developed. OBJECTIVE: The purpose of this case series is to describe the imaging findings of CALME and to review the current understanding of this recently described clinical entity with regard to clinical presentation, pathophysiology, differential diagnosis and treatment options. MATERIALS AND METHODS: This is a retrospective analysis of 3 girls, ages 5-7 years, who presented for imaging evaluation with subsequent pathologically proven CALME. Each child's clinical history, length of symptoms, imaging appearance and pathological findings were reviewed. RESULTS: All three girls presented with unilateral enlargement of the labium majus (two right-side, one left-side) with no history of trauma or other inciting cause. Two girls had painless labial enlargement that was recognized for weeks, and one had similar symptoms for 1 year prior to presentation. One girl was evaluated initially with sonography, and all three children underwent MR imaging. Sonographic evaluation showed asymmetrical labial enlargement without a definable mass. In each girl, the MR imaging findings were characterized by relatively ill-defined T1-weighted hypointense signal, T2-weighted hypo- to isointense signal with interspersed hyperintense septae, and heterogeneous patchy and feathery strands of enhancement on post-contrast imaging. Biopsy from each child showed benign fibrous tissue with intervening mature fibroadipose tissue, vessels and nerves without findings of inflammation or neoplasia. CONCLUSION: The MR imaging appearance of CALME is consistent. Recognition and appreciation of this unique pediatric entity by the radiologist may be essential for appropriate diagnosis and can help to guide therapy. Current preferred treatment approach is conservative.

Eccentric Capitellar Ossification Limits the Utility of the Radiocapitellar Line in Young Children.

BACKGROUND: The radiocapitellar line (RCL) has long been used for the radiographic evaluation of elbow alignment. In children, the capitellar ossific nucleus serves as a proxy for the entire capitellum, but this substitution has not been verified. Using magnetic resonance imaging (MRI), we sought to understand how maturation of the ossific nucleus of the capitellum affects the utility of RCL throughout skeletal maturation of the elbow. METHODS: The RCL was drawn on coronal and sagittal MRIs in 82 children (43 boys, 39 girls; age range, 1 to 13 y) with at least 3 patients in each 1-year interval age group. The perpendicular distance of the RCL from the center of both the cartilaginous capitellum and the capitellar ossific nucleus was measured relative to its total width, and a percent offset for each measurement was calculated. Logarithmic regression analysis was performed to analyze the effect of age and sex on percent offset. RESULTS: The RCL reliably intersected with the central third of the cartilaginous capitellum at all ages in both planes. Although the RCL intersected with the ossified capitellum in all but 3 measurements, it intersected with the central third of the ossified capitellum less often in younger children in both sagittal (B=0.47, P<0.001) and coronal (B=0.31, P=0.002) planes. Percent offset decreased significantly with age in a logarithmic manner in both sagittal (r=0.57, P<0.001) and coronal (r=-0.47, P<0.001) planes. 95% confidence intervals predict that the sagittal plane RCL will accurately intersect the central third of the ossified capitellum by age 10 years in girls and age 11 years in boys but not in the coronal plane. CONCLUSIONS: Eccentric ossification of the capitellum explains RCL variability in young children. The RCL does not reliably intersect the central third of the ossified capitellum until ages 10 years in girls and 11 years in boys in the sagittal plane. The RCL should be used within its limitations in skeletally immature children and should be combined with advanced imaging if necessary.

MRI findings of serous atrophy of bone marrow and associated complications.

OBJECTIVES: To report the MRI appearance of serous atrophy of bone marrow (SABM) and analyse clinical findings and complications of SABM. METHODS: A retrospective search of MRI examinations of SABM was performed. Symptoms, underlying conditions, MRI findings, delay in diagnosis and associated complications were recorded. RESULTS: We identified 30 patients (15 male, 15 female; mean age: 46 ± 21 years) with MRI findings of SABM. Underlying conditions included anorexia nervosa (n = 10), cachexia from malignant (n = 5) and non-malignant (n = 7) causes, massive weight loss after bariatric surgery (n = 1), biliary atresia (n = 1), AIDS (n = 3), endocrine disorders (n = 2) and scurvy (n = 1). MRI showed mildly hypointense signal on T1- weighted and hyperintense signal on fat-suppressed fluid-sensitive images of affected bone marrow in all cases and similar signal abnormalities of the adjacent subcutaneous fat in 29/30 cases. Seven patients underwent repeat MRI due to initial misinterpretation of bone marrow signal as technical error. Superimposed fractures of the hips and lower extremities were common (n = 14). CONCLUSIONS: SABM occurs most commonly in anorexia nervosa and cachexia. MRI findings of SABM are often misinterpreted as technical error requiring unnecessary repeat imaging. SABM is frequently associated with fractures of the lower extremities. KEY POINTS: • SABM occurs in several underlying conditions, most commonly anorexia nervosa and cachexia. • Abnormal marrow signal is often misinterpreted as technical error requiring unnecessary repeat imaging. • SABM is frequently associated with stress fractures. • Fractures in SABM can be obscured by marrow signal abnormality on MRI.

Juvenile Osteochondritis Dissecans: Correlation Between Histopathology and MRI.

OBJECTIVE: The objective of our study was to correlate specimens of juvenile osteochondritis dissecans (OCD) lesions of the knee to MRI examinations to elucidate the histopathologic basis of characteristic imaging features. MATERIALS AND METHODS: Five children (three boys and two girls; age range, 12-13 years old) who underwent transarticular biopsy of juvenile OCD lesions of the knee were retrospectively included in this study. Two radiologists reviewed the MRI examinations and a pathologist reviewed the histopathologic specimens and recorded characteristic features. Digital specimen photographs were calibrated to the size of the respective MR image with the use of a reference scale. Photographs were rendered semitransparent and over-laid onto the MR image with the location chosen on the basis of the site of the prior biopsy. RESULTS: A total of seven biopsy specimens were included. On MRI, all lesions showed cystlike foci in the subchondral bone, bone marrow edema pattern on proton density-or T2-weighted images, and relatively thick unossified epiphyseal cartilage. In four patients, a laminar signal intensity pattern was seen, and two patients had multiple breaks in the subchondral bone plate. Fibrovascular tissue was found at histopathology in all patients. Cleft spaces near the cartilage-bone interface and were seen in all patients while chondrocyte cloning was present in most cases. Focal bone necrosis and inflammation were infrequent MRI findings. Precise correlation of the MRI appearance to the histopathologic overlays consistently was found. CONCLUSION: A direct correlation exists between the histopathologic findings and the MRI features in patients with juvenile OCD. Additional studies are needed to correlate these MRI features with juvenile OCD healing success rates.

Quantitative Skeletal Muscle MRI: Part 1, Derived T2 Fat Map in Differentiation Between Boys With Duchenne Muscular Dystrophy and Healthy Boys.

OBJECTIVE: The purpose of this study was to validate derived T2 maps as an objective measure of muscular fat for discrimination between boys with Duchenne muscular dystrophy (DMD) and healthy boys. SUBJECTS AND METHODS: Forty-two boys with DMD (mean age, 9.9 years) and 31 healthy boys (mean age, 11.4 years) were included in the study. Age, body mass index, and clinical function scale grade were evaluated. T1-weighted MR images and T2 maps with and without fat suppression were obtained. Fatty infiltration was graded 0-4 on T1-weighted images, and derived T2 fat values (difference between mean T2 values from T2 maps with and without fat suppression) of the gluteus maximus and vastus lateralis muscles were calculated. Group comparisons were performed. The upper limit of the 95% reference interval of T2 fat values from the control group was applied. RESULTS: There was no significant difference in age or body mass index between groups. All healthy boys and 19 boys (45.2%) with DMD had a normal clinical function scale grade. Grade 1 fatty infiltration was seen in 90.3% (gluteus maximus) and 71.0% (vastus lateralis) of healthy boys versus 33.3% (gluteus maximus) and 52.4% (vastus lateralis) of boys with DMD. T2 fat values of boys with DMD were significantly longer than in the control group (p < 0.001). Using a 95% reference interval for healthy boys for the gluteus maximus (28.3 milliseconds) allowed complete separation from boys with DMD (100% sensitivity, 100% specificity), whereas the values for the vastus lateralis (7.28 milliseconds) resulted in 83.3% sensitivity and 100% specificity. CONCLUSION: Measurement of muscular fat with T2 maps is accurate for differentiating boys with DMD from healthy boys.