Pediatric Wrist

Pediatric wrist injuries pose unique diagnostic challenges due to distinct bone characteristics in children and their diverse injury patterns. The dynamic development of the wrist, marked by changes in bone age and emerging ossification centers, is crucial to evaluate growth and identify potential pathologies. The skeletal composition, rich in cartilage, renders bones relatively weaker yet more elastic, impacting their susceptibility to fracture. Forearm fractures display diverse patterns influenced by torsional forces. Scaphoid fractures, less common in children, differ from those in adults. Conditions like Madelung's deformity and ulnar variance are more common wrist disorders in the pediatric population. In addition, the scarcity and nonspecificity of symptoms in those with tendon injuries and triangular fibrocartilage complex lesions can be diagnostically challenging. This article reviews pediatric wrist injuries, emphasizing ossification patterns, common fracture types, and developmental variants. Grasping these complexities in pediatric wrist development and associated pathologies is essential for precise diagnosis and treatment.

Detection of early metaphyseal changes in a piglet model of Legg-Calvé-Perthes disease using quantitative mapping of MRI relaxation times

Legg-Calvé-Perthes disease (LCPD) is a childhood hip disorder characterized by ischemic injury to the epiphysis of the femoral head, but changes to the metaphysis have also been implicated in its pathogenesis. Quantitative magnetic resonance imaging (MRI) relaxation time mapping techniques are potentially useful to detect injury in LCPD, but studies to date have focused on the epiphysis. The purpose of this study was to assess whether T2, T1ρ, adiabatic T1ρ, and adiabatic T2ρ relaxation times can detect early metaphyseal changes in an LCPD piglet model. Complete epiphyseal ischemia of one femoral head was surgically induced and confirmed using contrast-enhanced MRI in n = 10 6-week-old piglets; the contralateral side was unoperated. The bilateral hips were imaged 1 week after surgery in vivo at 3T MRI using relaxation time mapping and contrast-enhanced MRI. Relaxation times and thicknesses of the metaphyseal primary and secondary spongiosa were measured and compared between the ischemic and contralateral-control femoral heads using paired t-tests. In the ischemic femoral heads, T2 relaxation times were significantly increased in the primary spongiosa (6.7 ± 9.8 ms, p = 0.029), and T2, T1ρ, adiabatic T1ρ, and adiabatic T2ρ relaxation times were significantly decreased in the secondary spongiosa (respectively: -13.3 ± 9.3 ms, p = 0.013; -32 ± 23 ms, p < 0.001; -43 ± 41 ms, p = 0.009; and -39 ± 13 ms, p < 0.001). The secondary spongiosa thickness was also significantly decreased in the ischemic femoral heads (p < 0.001). In conclusion, T2, T1ρ, adiabatic T1ρ, and adiabatic T2ρ relaxation time mapping techniques can detect early changes in the metaphysis following ischemic injury to the epiphysis of the femoral head in a piglet model of LCPD.

Analyzing lumbar vertebral shape and alignment in female patients with degenerative spondylolisthesis: Comparisons with spinal stenosis and risk factor exploration

PURPOSE

This study aimed to examine the vertebral body shape characteristics and spondylopelvic alignment in L4 degenerative spondylolisthesis (DS) as well as the risk factors for the development of DS.

METHODS

This cross-sectional study compared vertebral morphology and sagittal spinopelvic alignment in female patients with lumbar DS and lumbar spinal stenosis (LSS). The degree of lumbar lordosis (LL), pelvic incidence (PI), cross-sectional area (CSA), and vertebral body height ratio (ha/hp) of the lumbar spine were compared using full-length spine radiographs and computed tomography in 60 females with DS and in 60 women with LSS.

RESULTS

No significant differences in age or body mass index were observed between the two groups; however, the DS and LSS groups significantly differed in PI (mean, 58.9±10.8 vs. 47.2±11.6, P < 0.001), L4 CSA (mean, 1,166.2 m2 vs. 1,242.0 m2, P = 0.002) and ha/hp (mean, 1.134 vs. 1.007, P < 0.001). The L4 ha/hp was significantly higher in the DS group than in the LSS group. Additionally, LL values were negatively correlated with vertebral L5 CSA in the DS group (r = -0.28, P < 0.05). The LSS and DS groups demonstrated positive correlations between LL and L2, L3, and L4 ha/hp (r = 0.331, 0.267, and 0.317; P < 0.01, < 0.05, and < 0.05, respectively) and between LL and L4 and L5 ha/hp (r = 0.333, 0.331; P < 0.01, respectively). Multivariate regression analyses revealed that PI and ha/hp ratio may be independent predictors of DS development.

CONCLUSION

The DS group had significantly larger LL, PI, and L4 ha/hp and smaller L4 CSA than the LSS group. The lumbar vertebral body shape and sagittal spinopelvic alignment in females might be independent predictors of DS development.

Acute patellar dislocation: how skeletal maturity affects patterns of injury

OBJECTIVE

The main objective of this study was to understand the role of skeletal maturity in the different patterns of osteochondral and ligamentous injuries after an acute lateral patellar dislocation.

MATERIALS AND METHODS

Two radiologists independently reviewed MRIs of 212 knees performed after an acute lateral patellar dislocation to evaluate the presence of high-grade patellar osteochondral injury, femoral osteochondral injury, and medial patellofemoral ligament injury. The association of skeletal maturity (indicated by a closed distal femoral physis), age, sex, and first-time versus recurrent dislocation with each of these various lesions was analyzed using Chi-square or T test, and multivariable logistic regression with estimation of odds ratios (OR).

RESULTS

Skeletal maturity was significantly associated with high-grade patellar osteochondral injury [OR=2.72 (95% CI 1.00, 7.36); p=0.049] and femoral-side MPFL tear [OR=2.34 (95% CI 1.05, 5.25); p=0.039]. Skeletal immaturity was significantly associated with patellar-side MPFL tear [OR=0.35 (95% CI 0.14, 0.90); p=0.029].

CONCLUSION

Patterns of injury to the patella and medial patellofemoral ligament vary notably between the skeletally immature and mature, and these variations may be explained by the inherent weakness of the patellar secondary physis.

Specialist learning curves and clinical feasibility of introducing a new MRI grading system for skeletal maturity

Objective

MRI is an emerging imaging modality to assess skeletal maturity. This study aimed to chart the learning curves of paediatric radiologists when using an unfamiliar MRI grading system of skeletal maturity and to assess the clinical feasibility of implementing said system.

Methods

958 healthy paediatric volunteers were prospectively included in a dual-facility study. Each subject underwent a conventional MRI scan at 1.5 T. To perform the image reading, the participants were grouped into five subsets (subsets 1-5) of equal size (n∼192) in chronological order for scan acquisition. Two paediatric radiologists (R1-2) with different levels of MRI experience, both of whom were previously unfamiliar with the study's MRI grading system, independently evaluated the subsets to assess skeletal maturity in five different growth plate locations. Congruent cases at blinded reading established the consensus reading. For discrepant cases, the consensus reading was obtained through an unblinded reading by a third paediatric radiologist (R3), also unfamiliar with the MRI grading system. Further, R1 performed a second blinded image reading for all included subjects with a memory wash-out of 180 days. Weighted Cohen kappa was used to assess interreader reliability (R1 vs consensus; R2 vs consensus) at non-cumulative and cumulative time points, as well as interreader (R1 vs R2) and intrareader (R1 vs R1) reliability at non-cumulative time points.

Results

Mean weighted Cohen kappa values for each pair of blinded readers compared to consensus reading (interreader reliability, R1-2 vs consensus) were ≥0.85, showing a strong to almost perfect interreader agreement at both non-cumulative and cumulative time points and in all growth plate locations. Weighted Cohen kappa values for interreader (R1 vs R2) and intrareader reliability (R1 vs R1) were ≥0.72 at non-cumulative time points, with values ≥0.82 at subset 5.

Conclusions

Paediatric radiologists' clinical confidence when introduced to a new MRI grading system for skeletal maturity was high from the outset of their learning curve, despite the radiologists' varying levels of work experience with MRI assessment. The MRI grading system for skeletal maturity investigated in this study is a robust clinical method when used by paediatric radiologists and can be used in clinical practice.

Advances in knowledge

Radiologists with fellowship training in paediatric radiology experienced no learning curve progress when introduced to a new MRI grading system for skeletal maturity and achieved desirable agreement from the first time point of the learning curve. The robustness of the investigated MRI grading system was not affected by the earlier different levels of MRI experience among the readers.

Can diffusion tensor imaging unlock the secrets of the growth plate?

"How tall will I be?" Every paediatrician has been asked this during their career. The growth plate is the main site of longitudinal growth of the long bones. The chondrocytes in the growth plate have a columnar pattern detectable by diffusion tensor imaging (DTI). DTI shows the diffusion of water in a tissue and whether it is iso- or anisotropic. By detecting direction and magnitude of diffusion, DTI gives information about the microstructure of the tissue. DTI metrics include tract volume, length, and number, fractional anisotropy (FA), and mean diffusivity. DTI metrics, particularly tract volume, provide quantitative data regarding skeletal growth and, in conjunction with the fractional anisotropy, be used to determine whether a growth plate is normal. Tractography is a visual display of the diffusion, depicting its direction and amplitude. Tractography gives a more qualitative visualization of cellular orientation in a tissue and reflects the activity in the growth plate. These two components of DTI can be used to assess the growth plate without ionizing radiation or pain. Further refinements in DTI will improve prediction of post-imaging growth and growth plate closure, and assessment of the positive and negative effect of treatments like cis-retinoic acid and growth hormone administration.

Emergency MRI in Spine Trauma of Children and Adolescents-A Pictorial Review

Severe spinal trauma is uncommon in the pediatric population, but due to the potentially devastating consequences of missed injury, it poses a diagnostic challenge in emergency departments. Diagnostic imaging is often needed to exclude or confirm the injury and to assess its extent. Magnetic resonance imaging (MRI) offers an excellent view of both bony and soft tissue structures and their traumatic findings without exposing children to ionizing radiation. Our pictorial review aims to demonstrate the typical traumatic findings, physiological phenomena, and potential pitfalls of emergency MRI in the trauma of the growing spine.

MR Imaging of the Developing Pediatric Marrow: An Overview of Pearls and Pitfalls

The dynamic and developing pediatric skeleton is a well-elucidated process that occurs in a stepwise faction. Normal development has been reliably tracked and described with Magnetic Resonance (MR) imaging. The recognition of the normal patterns of skeletal development is essential, as normal development may mimic pathology and vice versa. The authors review normal skeleton maturation and the corollary imaging findings while highlighting common marrow imaging pitfalls and pathology.

Magnetic resonance and diffusion tensor imaging of the adolescent rabbit growth plate of the knee

PURPOSE

To assess the ability of MRI-DTI to evaluate growth plate morphology and activity compared with that of histomorphometry and micro-CT in rabbits.

METHODS

The hind limbs of female rabbits aged 16, 20, and 24 wk (n = 4 per age group) were studied using a 9.4T MRI scanner with a multi-gradient echo 3D sequence and DTI in 14 directions (b-value = 984 s/mm² ). After MRI, the right and left hind limb were processed for histological analysis and micro-CT, respectively. The Wilcoxon signed-rank test was used to evaluate the height and volume of the growth plate. Intraclass correlation and Pearson correlation coefficient were used to evaluate the association between DTI metrics and age.

RESULTS

The growth plate height and volume were similar for all modalities at each time point and age. Age was correlated with all tractography and DTI metrics in both the femur and tibia. A correlation was also observed between all the metrics at both sites. Tract number and volume declined with age; however, tract length did not show any changes. The fractional anisotropy color map showed lateral diffusion centrally in the growth plate and perpendicular diffusion in the hypertrophic zone, as verified by histology and micro-CT.

CONCLUSION

MRI-DTI may be useful for evaluating the growth plates.

Quantitative T2 and T1ρ mapping are sensitive to ischemic injury to the epiphyseal cartilage in an in vivo piglet model of Legg-Calvé-Perthes disease

OBJECTIVE

To determine if the quantitative MRI techniques T2 and T1ρ mapping are sensitive to ischemic injury to epiphyseal cartilage in vivo in a piglet model of Legg-Calvé-Perthes disease using a clinical 3T MRI scanner. We hypothesized that T2 and T1ρ relaxation times would be increased in the epiphyseal cartilage of operated vs contralateral-control femoral heads 1 week following onset of ischemia.

DESIGN

Unilateral femoral head ischemia was surgically induced in eight piglets. Piglets were imaged 1 week post-operatively in vivo at 3T MRI using a magnetization-prepared 3D fast spin echo sequence for T2 and T1ρ mapping and a 3D gradient echo sequence for cartilage segmentation. Ischemia was confirmed in all piglets using gadolinium contrast-enhanced MRI. Median T2 and T1ρ relaxation times were measured in the epiphyseal cartilage of the ischemic and control femoral heads and compared using paired t-tests. Histological assessment was performed on a subset of five piglets.

RESULTS

T2 and T1ρ relaxation times were significantly increased in the epiphyseal cartilage of the operated vs control femoral heads (ΔT2 = 11.9 ± 3.7 ms, 95% CI = [8.8, 15.0] ms, P < 0.0001; ΔT1ρ = 12.8 ± 4.1 ms, 95% CI = [9.4, 16.2] ms, P < 0.0001). Histological assessment identified chondronecrosis in the hypertrophic and deep proliferative zones within ischemic epiphyseal cartilage.

CONCLUSIONS

T2 and T1ρ mapping are sensitive to ischemic injury to the epiphyseal cartilage in vivo at clinical 3T MRI. These techniques may be clinically useful to assess injury and repair to the epiphyseal cartilage to better stage the extent of ischemic damage in Legg-Calvé-Perthes disease.

Diffusion Tensor Imaging of the Knee to Predict Childhood Growth

Background Accurate and precise methods to predict growth remain lacking. Diffusion tensor imaging (DTI) depicts the columnar structure of the physis and metaphyseal spongiosa and provides measures of tract volume and length that may help predict growth. Purpose To validate physeal DTI metrics as predictors of height velocity (1-year height gain from time of MRI examination) and total height gain (height gain from time of MRI examination until growth stops) and compare the prediction accuracy with bone age-based models. Materials and Methods Femoral DTI studies (b values = 0 and 600 sec/mm2; directions = 20) of healthy children who underwent MRI of the knee between February 2012 and December 2016 were retrospectively analyzed. Children with height measured at MRI and either 1 year later (height velocity) or after growth cessation (total height gain, mean = 34 months from MRI) were included. Physeal DTI tract volume and length were correlated with height velocity and total height gain. Multilinear regression was used to assess the potential of DTI metrics in the prediction of both parameters. Bland-Altman plots were used to compare root mean square error (RMSE) and bias in height prediction using DTI versus bone age methods. Results Eighty-nine children (mean age, 13 years ± 3 [SD]; 47 boys) had height velocity measured, and 70 (mean age, 14 years ± 1; 36 girls) had total height gain measured. Tract volumes correlated with height velocity (r2 = 0.49) and total height gain (r2 = 0.46) (P < .001 for both) after controlling for age and sex. Tract volume was the strongest predictor for height velocity and total height gain. An optimal multilinear model including tract volume improved prediction of height velocity (R2 = 0.63, RMSE = 1.7 cm) and total height gain (R2 = 0.59, RMSE = 1.8 cm) compared with bone age-based methods (height velocity: R2 = 0.32, RMSE = 2.9 cm; total height gain: R2 = 0.42, RMSE = 5.0 cm). Conclusion Models using tract volume derived from diffusion tensor imaging may perform better than bone age-based models in children for the prediction of height velocity and total height gain. © RSNA, 2022.

Imaging Review of Normal and Abnormal Skeletal Maturation

The growing skeleton undergoes well-described and predictable normal developmental changes, which may be misinterpreted a as pathologic condition at imaging. Primary and secondary ossification centers (SOCs), which form the diaphysis and the epiphysis of long bones, respectively, are formed by endochondral and intramembranous ossification processes. During skeletal maturation, the SOCs may appear irregular and fragmented, which should not be confused with fractures, osteochondritis dissecans, and osteochondrosis. These normal irregularities are generally symmetric with a smooth, round, and sclerotic appearance, which are aspects that help in the differentiation. The metaphysis, epiphysis, and growth plates or physes are common sites of injuries and normal variants in the pediatric skeleton. The metaphysis contains the newly formed bone from endochondral ossification and is highly vascularized. It is predisposed to easy spread of infections and bone tumors. The physis is the weakest structure of the immature skeleton. Injuries to this location may disrupt endochondral ossification and lead to growth disturbances. Pathologic conditions of the epiphyses may extend into the articular surface and lead to articular damage. At MRI, small and localized foci of bone marrow changes within the epiphysis and metaphysis are also a common finding. These can be related to residual red marrow (especially in the metaphysis of long bones and hindfoot), focal periphyseal edema (associated with the process of physeal closure), and ultimately to a normal ossification process. The authors review the imaging appearance of normal skeletal maturation and discuss common maturation disorders on the basis of developmental stage and location. ^©RSNA, 2022.

ACR Appropriateness Criteria® Osteomyelitis or Septic Arthritis-Child (Excluding Axial Skeleton)

Imaging plays an integral role in the evaluation of suspected musculoskeletal infections in children, not only in the accurate identification of infection such as osteomyelitis or septic arthritis, but also in guiding management. Various diagnostic modalities serve different purposes in the assessment of suspected pediatric musculoskeletal infections. The purpose of this document is to provide imaging guidance in the most frequently encountered clinical scenarios in which osteomyelitis and/or septic arthritis are suspected, outside of the axial skeleton. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion.

Musculoskeletal imaging in neonates: use of ultrasound

High-resolution US is a practical, cost-effective modality to evaluate the musculoskeletal system in neonates. US can be performed portably in the neonatal intensive care unit so that the critically ill infant can be evaluated with minimal distress. Sonography is noninvasive and does not require sedation; typical questions that might require the use of MRI or CT in older children can be rapidly resolved with US. Dynamic imaging can be used in real time to stress joints and see how articular structures relate. Given the advantages of US within the neonatal population, it has been widely used to evaluate for neonatal fractures, congenital joint abnormalities, limb deficiencies as well as muscular and soft-tissue abnormalities.

T1ρ and T2 mapping detect acute ischemic injury in a piglet model of Legg-Calvé-Perthes disease

This study investigated the sensitivity of T1ρ and T2 relaxation time mapping to detect acute ischemic injury to the secondary ossification center (SOC) and epiphyseal cartilage of the femoral head in a piglet model of Legg-Calvé-Perthes disease. Six piglets underwent surgery to induce global right femoral head ischemia and were euthanized 48 h later. Fresh operated and contralateral-control femoral heads were imaged ex vivo with T1, T2, and T1ρ mapping using a 9.4T magnetic resonance imaging scanner. The specimens were imaged a second time after a freeze/thaw cycle and then processed for histology. T1, T2, and T1ρ measurements in the SOC, epiphyseal cartilage, articular cartilage, and metaphysis were compared between operated and control femoral heads using paired t tests. The effects of freeze/thaw, T1ρ spin-lock frequency, and fat saturation were also investigated. Five piglets with histologically confirmed ischemic injury were quantitatively analyzed. T1ρ was increased in the SOC (101 ± 15 vs. 73 ± 16 ms; p = 0.0026) and epiphyseal cartilage (84.9 ± 9.2 vs. 74.3 ± 3.6 ms; p = 0.031) of the operated versus control femoral heads. T2 was also increased in the SOC (28.7 ± 2.0 vs. 22.7 ± 1.7; p = 0.0037) and epiphyseal cartilage (57.4 ± 4.7 vs. 49.0 ± 2.7; p = 0.0041). No changes in T1 were detected. The sensitivities of T1ρ and T2 mapping in detecting ischemic injury were maintained after a freeze/thaw cycle, and T1ρ sensitivity was maintained after varying spin-lock frequency and applying fat saturation. In conclusion, T1ρ and T2 mapping are sensitive in detecting ischemic injury to the SOC and epiphyseal cartilage of the femoral head as early as 48 h after ischemia induction.

Pearls and Pitfalls of Imaging of the Developing Pediatric Skeleton: Differentiating Normal and Pathology With MRI

Developmental changes occurring in the pediatric skeleton throughout childhood cause imaging appearances that may be confused with pathology. Knowledge of the typical pattern of red to yellow bone marrow conversion and areas of normal developmental irregular ossification is essential for radiologists interpreting musculoskeletal imaging in children to avoid mistaking normal findings for disease. Here we review the normal conversion of hematopoietic to yellow marrow on pediatric MRI and illustrate how MRI can distinguish the normal areas of irregular ossification from various pathology that can occur at and around growth centers in the developing skeleton.

T2 mapping of the acetabular cartilage in infants and children with developmental dysplasia of the hip

BACKGROUND

T2 mapping is useful for evaluating the cartilage matrix.

PURPOSE

To determine the variations in the acetabular cartilage T2 relaxation values between healthy individuals and those with developmental dysplasia of the hip (DDH).

MATERIAL AND METHODS

Thirty-three patients with unilateral DDH underwent 3-T magnetic resonance imaging (MRI) between January 2018 and February 2019. Fifteen volunteers (30 hips) were enrolled as controls. T2 values were measured with the T2 mapping sequence in all layers and were equally divided into three layers (deep, middle, and superficial) with equal thickness. We calculated the mean T2 relaxation values for the full thickness, deep, middle, and superficial layers and compared the values between the different groups. In addition, the inter- and intra-observer agreements were calculated.

RESULTS

The T2 relaxation values in the DDH arm were significantly lower in the middle, superficial, and full thickness layers compared with those of the volunteers and contralateral hips. The T2 relaxation values of the deep layers showed no significant difference between the different groups. The acetabular cartilage T2 relaxation values increased from the deep layer to the superficial layer in the control and contralateral groups. Both inter- and intra-observer agreements were good.

CONCLUSION

MRI T2 mapping may help to diagnose developmental disorders of the acetabular cartilage matrix in infants and children with DDH. Abnormal acetabular cartilage T2 relaxation values may be due to the extraordinary stress load of the femoral head.

Sports-Related Injuries of the Pediatric Musculoskeleton

Worldwide, more than 50 million children and adolescents participate in organized athletic programs annually. Despite the numerous health and well-being benefits, this widespread involvement also leads to acute and overuse injuries that account for millions of medical visits each year. Musculoskeletal injury in childhood may lead to growth disturbance and lifelong disability. Imaging plays a critical role in the diagnosis and management of these injuries. While radiography is sufficient for most long bone fractures, MRI is often necessary for optimal evaluation of injuries involving the radiolucent growth mechanism and articular structures. The following review will discuss the imaging features associated with many sports-related injuries unique to the pediatric musculoskeleton, specifically the lower extremity.

Imaging of pediatric bone and growth disorders: Of diagnostic workhorses and new horizons

Children and adolescents with bone and growth disorders require interdisciplinary care from various specialists including pediatric radiologists with a focus on musculoskeletal disorders. This article covers routine topics, differential diagnoses, and selected research imaging in children with osteogenesis imperfecta (OI), X‑linked hypophosphatemic rickets (XLH), achondroplasia, and other bone and growth disorders from the standpoint of a tertiary referral center.

MRI risk factors for development of avascular necrosis after closed reduction of developmental dysplasia of the hip: Predictive value of contrast-enhanced MRI

Purpose

The purpose of this study was to identify imaging risk factors on contrast-enhanced hip MRI after closed reduction of developmental dysplasia of the hip (DDH) that could predict future development of avascular necrosis (AVN) of the femoral head.

Materials and methods

Fifty-eight infants (F: M = 53: 5, aged 3–18 months) who underwent immediate postoperative contrast-enhanced hip MRI after closed reduction of DDH were included in this study. Quality of reduction (concentric vs eccentric reduction with or without obstacles), abduction angle of the hip, presence of ossific nucleus, and pattern of contrast enhancement of the femoral head were retrospectively evaluated on MRI. Interobserver agreement of contrast enhancement pattern on MRI were evaluated by two radiologists. Development of AVN was determined through radiographic findings at 1 year after reduction.

Results

AVN of the femoral head developed in 13 (22%) of 58 patients. Excessive abduction of the hip joint (OR 4.65, [95% CI 1.20, 18.06] and global decreased enhancement of the femoral head (OR 71.66, [95% CI 10.54, 487.31]) exhibited statistically significant differences between the AVN and non-AVN groups (P < 0.05). Eccentric reduction (P = 0.320) did not show statistically significant difference between two groups and invisible ossific nucleus (P = 0.05) showed borderline significance. Multi-variable logistic regression indicated that global decreased enhancement of the femoral head was a significant risk factor of AVN (OR 27.92, 95% CI [4.17, 350.18]) (P = 0.0031). Interobserver agreement of contrast enhancement pattern analysis and diagnosis of AVN were good (0.66, 95% CI [0.52, 0.80]).

Conclusion

Contrast-enhanced hip MRI provides accurate anatomical assessment of the hip after closed reduction of DDH. Global decreased enhancement of the femoral head could be used as a good predictor for future development of AVN after closed reduction of DDH.

Pitfalls in MRI of the Developing Pediatric Ankle

Normal skeletal development in the pediatric ankle is dynamic and often produces variable imaging appearances that are subject to misinterpretation. Radiologists must understand the underlying developmental phenomena, such as endochondral and membranous ossification and physeal fusion, and be familiar with their common and uncommon imaging manifestations unique to the pediatric ankle. This is especially true as the use of MRI in the evaluation of musculoskeletal trauma expands among younger populations. The authors focus on MRI evaluation of the skeletally maturing pediatric ankle and present pearls for accurately distinguishing normal findings and imaging pitfalls from true pathologic findings. The normal but often variable imaging findings of preossification, secondary ossification, and multiple ossification centers, as well as the range of bone marrow signal intensities that can be visualized within ossification centers, are described, along with tips to help differentiate these from true pathologic findings such as contusion, fracture, or tumor. The authors also review dynamic periosteal and physeal contributions to bone growth to highlight helpful distinguishing features and avoid misdiagnosis of common subperiosteal and periphyseal abnormalities. For example, the normal trilaminar appearance of the immature cortex and periosteum should not be mistaken for periosteal reaction, traumatic stripping, or subperiosteal hematoma. In addition, the physis can have several confusing but normal appearances, including normal physeal undulations (eg, Kump bump) or focal periphyseal edema, which should not be mistaken for pathologic findings such as physeal fracture, infection, or bar. ^©RSNA, 2020.

Comparison of reliability of magnetic resonance imaging using cartilage and T1-weighted sequences in the assessment of the closure of the growth plates at the knee

Background

Growth development is traditionally evaluated with plain radiographs of the hand and wrist to visualize bone structures using ionizing radiation. Meanwhile, MRI visualizes bone and cartilaginous tissue without radiation exposure.

Purpose

To determine the state of growth plate closure of the knee in healthy adolescents and young adults and compare the reliability of staging using cartilage sequences and T1-weighted (T1W) sequence between pediatric and general radiologists.

Material and Methods

A prospective, cross-sectional study of MRI of the knee with both cartilage and T1W sequences was performed in 395 male and female healthy subjects aged between 14.0 and 21.5 years old. The growth plate of the femur and the tibia were graded using a modified staging scale by two pediatric and two general radiologists. Femur and tibia were graded separately with both sequences.

Results

The intraclass correlation was overall excellent. The inter- and intra-observer agreement for pediatric radiologists on T1W was 82% (κ = 0.73) and 77% (κ = 0.65) for the femur and 90% (κ = 0.82) and 87% (κ = 0.75) for the tibia. The inter-observer agreement for general radiologists on T1W was 69% (κ = 0.56) for the femur and 56% (κ = 0.34) for the tibia. Cohen’s kappa coefficient showed a higher inter- and intra-observer agreement for cartilage sequences than for T1W: 93% (κ = 0.86) and 89% (κ = 0.79) for the femur and 95% (κ = 0.90) and 91% (κ = 0.81) for the tibia.

Conclusion

Cartilage sequences are more reliable than T1W sequence in the assessment of the growth plate in adolescents and young adults. Pediatric radiology experience is preferable.

[Lower leg, ankle and foot]

CLINICAL/METHODICAL ISSUE

Bipedal locomotion means high mechanical stress on the lower extremities and susceptibility to fractures. On the one hand, these can be the result of a one-time traumatic stress in the context of high speed traumas or falls, but can also result from repetitive microtraumas with subsequent stress fractures.

STANDARD RADIOLOGICAL METHODS

For all fracture entities and localizations, X‑ray diagnostics is the basic modality.

METHODICAL INNOVATIONS

For optimal surgical reconstruction of intra-articular fractures or in complex fracture configurations, computed tomography should be generously used to improve postoperative outcome.

PERFORMANCE

The classification of the individual fractures should enable standardised further therapy planning, especially with regard to conventional or surgical treatment.

ACHIEVEMENTS

The combination of X‑ray, magnetic resonance imaging and computed tomography makes a reliable diagnosis regarding foot fractures possible.

PRACTICAL RECOMMENDATIONS

Important for the use of individual classification systems is always, in addition to clinical relevance, the safe and equal understanding of the individual types and degrees by the radiologist and the referring colleague.

MRI evaluation of articular cartilage in patients with juvenile osteochondritis dissecans (JOCD) using T2∗ mapping at 3T

OBJECTIVE

Evaluate articular cartilage by magnetic resonance imaging (MRI) T2∗ mapping within the distal femur and proximal tibia in adolescents with juvenile osteochondritis dissecans (JOCD).

DESIGN

JOCD imaging studies acquired between August 2011 and February 2019 with clinical and T2∗ mapping MRI knee images were retrospectively collected and analyzed for 31 participants (9F/22M, 15.0 ± 3.8 years old) with JOCD lesions in the medial femoral condyle (MFC). In total, N = 32 knees with JOCD lesions and N = 14 control knees were assessed. Mean T2∗ values in four articular cartilage regions-of-interest (MFC, lateral femoral condyle (LFC), medial tibia (MT), and lateral tibia (LT)) and lesion volume were measured and analyzed using Wilcoxon-rank-sum tests and Spearman correlation coefficients (R).

RESULTS

Mean ± standard error T2∗ differences observed between the lesion-sided MFC and the LFC in JOCD-affected knees (28.5 ± 0.9 95% confidence interval [26.8, 30.3] vs 26.3 ± 0.7 [24.8, 27.7] ms, P = 0.088) and between the affected- and control-knee MFC (28.5 ± 0.9 [26.8, 30.3] vs 28.5 ± 0.6 [27.1, 29.9] ms, P = 0.719) were nonsignificant. T2∗ was significantly increased in the lesion-sided MT vs the LT for the JOCD-affected knees (21.5 ± 0.7 [20.1, 22.9] vs 18.0 ± 0.7 [16.5, 19.5] ms, P = 0.002), but this same difference was also observed between the MT and LT in control knees (21.0 ± 0.6 [19.7, 22.3] vs 18.1 ± 1.1 [15.8, 20.4] ms, P = 0.037). There was no significant T2∗ difference between the affected- and control-knee MT (21.5 ± 0.7 [20.1, 22.9] vs 21.0 ± 0.6 [19.7, 22.3] ms, P = 0.905). T2∗ within the lesion-sided MFC was not correlated with patient age (R = 0.20, P = 0.28) or lesion volume (R = 0.06, P = 0.75). T2∗ values were slightly increased near lesions in later-stage JOCD subjects but without statistical significance.

CONCLUSIONS

T2∗ relaxations times were not significantly different from control sites in the articular cartilage overlying JOCD lesions in the MFC or adjacent MT cartilage in early-stage JOCD.

Application of knee MRI in forensic age estimation: A retrospective cohort

INTRODUCTION

Forensic age estimation is performed via clinical examination and utilizing various imaging modalities. Currently, radiography and CT are used. In this study we aim to evaluate if magnetic resonance imaging (MRI) can be used to determine stages of fusion in the epiphysis of the tibia and femur, and if these stages are significantly different regarding the mean age of subjects classified in each one.

METHODS

A total of 193 subjects were included in the study. Knee MR imaging was performed on all of the patients, and the patients were categorized based on imaging findings of the tibial and femoral epiphysis. Tukey multiple comparison test and analysis of variance were used to assess if the difference in the mean age of the groups were significantly different.

RESULTS

Analysis of variance revealed that the mean of the five groups, both in tibia and femur imaging were significantly different. Analysis of variance showed that in most of the cases, the groups mean age significantly differed from the other groups. Tukey multiple comparison tests showed that although the differences between stages I-III could not be regarded as significant, MR imaging was suitable in distinguishing stages IV-V from stages I-III.

CONCLUSION

MR imaging of the knee may be a suitable imaging modality to assess an individual's age, does not involve ionizing radiation, and that with imaging a single anatomical location, at least two epiphyses could be used to determine the age.

IMPLICATIONS FOR PRACTICE

Utilization of knee MRI by clinicians as a safe and practical age estimation method.

The distal radial physis: Exploring normal anatomy on MRI enables interpretation of stress related changes in young gymnasts

Rationale: Explore the MRI-appearance of the healthy distal radial physis and the distribution of stress-related changes in physeal thickness in young gymnasts to aid in the understanding of the pathophysiological process of stress-related physeal injury. Methods: Symptomatic gymnasts with clinically suspected overuse injury of the distal radial physis and age and gender-matched asymptomatic gymnasts and healthy non-gymnasts underwent an MRI-scan of the wrist. A cartilage-specific sequence was used to obtain three-dimensional reconstructions of the distal radial physis. Heat maps and line charts of these reconstructions visualised distribution of physeal thickness per study group and were used to explore differences between study groups. Symptomatic gymnasts displaying the most profound physeal widening (n = 10) were analysed separately. Results: Twenty-seven symptomatic - (skeletal age 12.9 ± 1.5 years), 16 asymptomatic - (skeletal age 12.8 ± 1.9 years) and 23 non-gymnasts (skeletal age 13.6 ± 1.9 years) were included for analysis. Physes of healthy non-gymnasts had a thin centre and increased in thickness towards the borders. Gymnasts demonstrated an increase in thickness of the entire physeal surface. In symptomatic gymnasts increase in physeal thickness was most prominent at the volar side when compared to asymptomatic gymnasts and non-gymnasts. Conclusion: The healthy distal radial physis is characterised by a thin centre surrounded by thicker borders. Stress applied to the wrist during gymnastics causes an overall increase in physeal thickness. Profound thickness increase is present at the volar side of the physis mainly in symptomatic gymnasts. These results can help unravel the pathophysiological mechanism of stress-related physeal injury in gymnasts and aid early injury identification.

Three-Dimensional Quantitative Magnetic Resonance Imaging of Epiphyseal Cartilage Vascularity Using Vessel Image Features: New Insights into Juvenile Osteochondritis Dissecans

We introduce a quantitative measure of epiphyseal cartilage vascularity and examine vessel networks during human skeletal maturation. Understanding early morphological changes in the distal femoral condyle is expected to provide information on the pathogenesis of developmental diseases such as juvenile osteochondritis dissecans.

Methods

Twenty-two cadaveric knees from donors ranging from 1 month to 10 years of age were included in the study. Images of bone, cartilage, and vascularity were acquired simultaneously with a 3-dimensional gradient-recalled-echo magnetic resonance imaging (MRI) sequence. The secondary ossification center volume and total epiphysis cartilage volume ratio and articular-epiphyseal cartilage complex and epiphyseal cartilage widths were measured. Epiphyseal cartilage vascularity was visualized for 9 data sets with quantitative susceptibility mapping and vessel filtering, resulting in 3-dimensional data to inform vessel network segmentation and to calculate vascular density.

Results

Three distinct, non-anastomosing vascular networks (2 peripheral and 1 central) supply the distal femoral epiphyseal cartilage. The central network begins regression as early as 3 months and is absent by 4 years. From 1 month to 3 years, the ratio of central to peripheral vascular area density decreased from 1.0 to 0.5, and the ratio of central to peripheral vascular skeletal density decreased from 0.9 to 0.6. A narrow, peripheral vascular rim was present at 8 years but had disappeared by 10 years. The secondary ossification center progressively acquires the shape of the articular-epiphyseal cartilage complex by 8 years of age, and the central areas of the medial and lateral femoral condyles are the last to ossify.

Conclusions

Using cadaveric pediatric knees, we provide quantitative, 3-dimensional measures of epiphyseal cartilage vascular regression during skeletal development using vessel image features. Central areas with both early vascular regression and delayed ossification correspond to predilection sites of juvenile osteochondritis dissecans in this limited case series. Our findings highlight specific vascular vulnerabilities that may lead to improved understanding of the pathogenesis and better-informed clinical management decisions in developmental skeletal diseases.

Clinical Relevance

This paradigm shift in understanding of juvenile osteochondritis dissecans etiology and disease progression may critically impact future patient management. Our findings highlight specific vascular vulnerabilities during skeletal maturation in a group of active young patients seen primarily by orthopaedic surgeons and sports medicine professionals.

It's a thin line: development and validation of Dixon MRI-based semi-quantitative assessment of stress-related bone marrow edema in the wrists of young gymnasts and non-gymnasts

Purpose

To assess reliability and clinical utility of evaluating stress-related metaphyseal water distribution using a semi-quantitative Dixon MRI-based method for early diagnosis of physeal stress injuries in adolescent gymnasts.

Methods

Twenty-four gymnasts with clinically suspected overuse injury of the distal radial physis, 18 asymptomatic gymnasts, and 24 non-gymnast controls aged 12 ± 1.5 years prospectively underwent hand radiographs and 3T MRI of the wrist including coronal T1-weighted and T2-weighted Dixon sequences. Two raters measured metaphyseal water signal fraction in 13 radial and ulnar regions of interest (ROI). Inter- and intrarater reliability, interslice (between 3 middle radial slices), and inter-ROI (between 3 ROIs on same level) reliability were assessed using intraclass correlation coefficients (ICC). Water signal fractions and their within-person ratios in distal versus most proximal ROIs were compared between groups using one-way analysis of variance.

Results

Inter- and intrarater ICCs were 0.79–0.99 and 0.94–1.0 for T1-weighted, and 0.88–1.0 and 0.88–1.0 for T2-weighted Dixon. Interslice and inter-ROI ICCs were 0.55–0.94 and 0.95–0.97 for T1-weighted, and 0.70–0.96 and 0.96–0.97 for T2-weighted Dixon. Metaphyseal water signal fraction in symptomatic gymnasts was higher in six distal ROIs compared with asymptomatic gymnasts and in nine ROIs compared with non-gymnasts (p < 0.05). Metaphyseal water score (ratio of distal versus most proximal ROIs) was 1.61 in symptomatic gymnasts and 1.35 in asymptomatic gymnasts on T2-weighted Dixon (p < 0.05).

Conclusion

Semi-quantitative Dixon MRI-based water signal fraction assessment has good to excellent reproducibility and shows increased metaphyseal water scores in symptomatic gymnasts compared with asymptomatic gymnastic peers.

Key Points

• The proposed Dixon MRI-based semi-quantitative method for assessment of metaphyseal bone marrow water content is reliable, with off-the-shelf availability and short scan times.

• The metaphyseal water score allows comparisons between gymnasts using a within-person reference area for unaffected metaphyseal bone.

• As metaphyseal water score was increased in symptomatic gymnasts compared with asymptomatic gymnasts, this semi-quantitative method can potentially be used as an indicator of bone marrow edema in the early diagnosis of gymnastic physeal stress injury.

Electronic supplementary material

The online version of this article (10.1007/s00330-019-06446-8) contains supplementary material, which is available to authorized users.

Physeal bridges: causes, diagnosis, characterization and post-treatment imaging

The cartilaginous primary physis, or growth plate, at the end of long bones in children allows for longitudinal bone growth. A variety of insults to the physis can lead to physeal bridge formation, which in turn can lead to limb-shortening and angular deformities. This paper begins with a description of the causes, risk factors and mechanisms by which bridges form. Then it reviews the use of imaging in the diagnosis and characterization of bridges and in the evaluation of treatment and post-treatment complications. It is important for radiologists taking care of children to be aware of the indirect and direct imaging findings of physeal bridges to aid in their diagnosis, to be able to characterize bridges as part of preoperative planning, and to know the imaging finding of post-resection complications.

Radiographic/MR Imaging Correlation of the Pediatric Knee Growth

Normal bone growth of the pediatric knee as well as normal variants of ossification result in different appearances that can be identified on imaging (radiography/MR imaging). Familiarity with these changes is important to avoid confusing normal growth with pathology. This article illustrates the main features related to normal bone growth (growth arrest lines, physeal changes, ossification centers within the epiphysis, hematopoietic marrow within the metaphysis) and physis disappearance (« FOPE »). Variants in femur (epiphyseal irregularities, subchondral anomalies of posterior condyles, periosteal desmoid), tibia (tibial tuberosity ossification), and patella (dorsal defect, bipartite patella, lower pole fragmentation) are also described.

Finite element modelling of the developing infant femur using paired CT and MRI scans

Bone finite element (FE) studies based on infant post-mortem computed tomography (CT) examinations are being developed to provide quantitative information to assist the differentiation between accidental and inflicted injury, and unsuspected underlying disease. As the growing skeleton contains non-ossified cartilaginous regions at the epiphyses, which are not well characterised on CT examinations, it is difficult to evaluate the mechanical behaviour of the developing whole bone. This study made use of paired paediatric post mortem femoral CT and magnetic resonance imaging (MRI) examinations at two different stages of development (4 and 7 months) to provide anatomical and constitutive information for both hard and soft tissues. The work aimed to evaluate the effect of epiphyseal ossification on the propensity to shaft fractures in infants. The outcomes suggest that the failure load of the femoral diaphysis in the models incorporating the non-ossified epiphysis is within the range of bone-only FE models. There may however be an effect on the metaphysis. Confirmation of these findings is required in a larger cohort of children.

Imaging of the limping child

Limping is a challenging symptom in the pediatric patient as the diagnosis can range from traumatic, malformative, infectious/inflammatory and neoplastic diseases. In this paper, we propose a schematic imaging algorithm to the limping child in three different age groups (Toddler: 1-3years, child: 4-10 years; adolescent: 11-16 years) based on presence of signs of infection, any specific localization of pain, and history of trauma. In this setting, the most common imaging pitfalls are also summarised. Finally, a literature review of the main differential causes of limping in the pediatric patient is reported.

The embryonic and evolutionary boundaries between notochord and cartilage: a new look at nucleus pulposus-specific markers

The adult nucleus pulposus (NP) and articular cartilage are similar in terms of their histocytological components and biomechanical functionalities, requiring a deep understanding of NP-specific markers to better evaluate stem-cell-based NP regeneration. Here, we seek to distinguish NP cells from articular chondrocytes (ACs), focusing on differences in their embryonic formation and evolutionary origin. Embryonically, NP cells are conservatively derived from the axial notochord, whereas ACs originate in a diversified manner from paraxial mesoderm and neural crest cells. Evolutionarily, although the origins of vertebrate NP and AC cells can be traced to similar structures within protostomia-like bilaterian ancestors, the distant phylogenetic relationship between the two groups of animals and the differences in the bodily origins of the tissues suggest that the tissues may in fact have undergone parallel evolution within the protostomia and deuterostomia. The numbers of supposedly NP-specific markers are increasing gradually as microarray studies proceed, but no final consensus has been attained on the specificity and physiology of "exclusive" NP markers because of innate variations among species; intrinsic expression of genes that destabilize the circadian clock; and cooperation by, and crosstalk among, different genes in terms of physiology-related phenotypes. We highlight the embryonic and evolutionary boundaries between NP and AC cells, to aid in recognition of the challenges associated with evaluation of the role played by nucleopulpogenic differentiation during stem-cell-based intervertebral disc regeneration.

Systematic assessment of the growth plates of the wrist in young gymnasts: development and validation of the Amsterdam MRI assessment of the Physis (AMPHYS) protocol

Objectives

To develop and validate a protocol for MRI assessment of the distal radial and ulnar periphyseal area in gymnasts and non-gymnasts.

Methods

Twenty-four gymnasts with wrist pain, 18 asymptomatic gymnasts and 24 non-gymnastic controls (33 girls) underwent MRI of the wrist on a 3T scanner. Sequences included coronal proton density-weighted images with and without fat saturation, and three-dimensional water-selective cartilage scan and T2 Dixon series. Skeletal age was determined using hand radiographs. Three experienced musculoskeletal radiologists established a checklist of possible (peri)physeal abnormalities based on literature and clinical experience. Five other musculoskeletal radiologists and residents evaluated 30 MRI scans (10 from each group) using this checklist and reliability was determined using the intraclass correlation coefficient (ICC) and Fleiss' kappa. A final evaluation protocol was established containing only items with fair to excellent reliability.

Results

Twenty-seven items were assessed for reliability. Intra-rater and inter-rater agreement was good to excellent (respective ICCs 0.60-0.91 and 0.60-0.78) for four epiphyseal bone marrow oedema-related items, physeal signal intensity, metaphyseal junction and depth of metaphyseal intrusions. For physeal thickness, thickness compared with proximal physis of first metacarpal, metaphyseal intrusions, physeal connection of intrusions and metaphyseal bone marrow signal intensity, intra-rater agreement was fair to excellent (ICC/kappa 0.55-0.85) and inter-rater agreement was fair (ICC/kappa 0.41-0.59). Twelve items were included in the final protocol.

Conclusion

The Amsterdam MRI assessment of the Physis protocol facilitates patient-friendly and reliable assessment of the (peri)physeal area in the radius and ulna.

Sexual Dimorphism and the Origins of Human Spinal Health

Recent observations indicate that the cross-sectional area (CSA) of vertebral bodies is on average 10% smaller in healthy newborn girls than in newborn boys, a striking difference that increases during infancy and puberty and is greatest by the time of sexual and skeletal maturity. The smaller CSA of female vertebrae is associated with greater spinal flexibility and could represent the human adaptation to fetal load in bipedal posture. Unfortunately, it also imparts a mechanical disadvantage that increases stress within the vertebrae for all physical activities. This review summarizes the potential endocrine, genetic, and environmental determinants of vertebral cross-sectional growth and current knowledge of the association between the small female vertebrae and greater risk for a broad array of spinal conditions across the lifespan.

Imaging of Pediatric Growth Plate Disturbances

The growth plates, or physes, are visible on virtually all images obtained in skeletally immature children. The proper function of these growth plates depends on an intricate balance between chondrocyte proliferation, which requires nourishment from the epiphyseal vessels, and chondrocyte death, which requires the integrity of the metaphyseal vessels. Therefore, injury to the growth plate (ie, direct insult) or vascular compromise on either side of the growth plate (ie, indirect insult) can cause growth plate dysfunction. Direct growth plate insults occur most commonly with Salter-Harris fractures, and injuries that allow the transphyseal communication of vessels are at a higher risk for subsequent transphyseal bone bridge formation. Indirect insults lead to different sequelae that are based on whether the epiphyseal blood supply or metaphyseal blood supply is compromised. Epiphyseal osteonecrosis can result in slowed longitudinal bone growth, with possible growth plate closure, and is often accompanied by an abnormal secondary ossification center. In contrast, the disruption of metaphyseal blood supply alters endochondral ossification and allows the persistence of chondrocytes within the metaphysis, which appear as focal or diffuse growth plate widening. Imaging remains critical for detecting acute injuries and identifying subsequent growth disturbances. Depending on the imaging findings and patient factors, these growth disturbances may be amenable to conservative or surgical treatment. Therefore, an understanding of the anatomy and physiologic features of the normal growth plate and the associated pathophysiologic conditions can increase diagnostic accuracy, enable radiologists to anticipate future growth disturbances, and ensure optimal imaging, with the ultimate goal of timely and appropriate intervention. ^©RSNA, 2017.

Physeal bar equivalent

Premature partial physeal arrest without the formation of an osseous bar - physeal bar equivalent (PBE) - is uncommon. Four children with a PBE had an infection near the distal femoral physis before the age of 11 months. Some growth was achieved after resection of the PBE in each case. Of two cases diagnosed and treated early, one required only contralateral physeal arrests to achieve limb-length equality at maturity. The other, currently 8 years and 4 months old, has a 1.1-cm limb-length discrepancy 6 years after PBE resection and will require observation until maturity. Of two cases diagnosed and treated late, one required ipsilateral femoral lengthening and contralateral femoral shortening and physeal arrests to treat the limb-length discrepancy and angular deformity. The other, currently 7 years and 1 month old, has a 4.8-cm discrepancy and will need future surgical limb-length equalization. Early recognition and treatment of PBE is required to avoid severe limb-length inequality and angular deformity.

Imaging of Sports-related Injuries of the Lower Extremity in Pediatric Patients

With increasing participation and intensity of training in youth sports in the United States, the incidence of sports-related injuries is increasing, and the types of injuries are shifting. In this article, the authors review sports injuries of the lower extremity, including both acute and overuse injuries, that are common in or specific to the pediatric population. Common traumatic injuries that occur in individuals of all ages (eg, tears of the acetabular labrum and anterior cruciate ligament) are not addressed, although these occur routinely in pediatric sports. However, some injuries that occur almost exclusively in high-level athletes (eg, athletic pubalgia) are reviewed to increase awareness and understanding of these entities among pediatric radiologists who may not be familiar with them and thus may not look for them. Injuries are described according to their location (ie, hip, knee, or foot and ankle) and pathologic process (eg, apophysitis, osteochondritis dissecans). Examples of abnormalities and normal variants of the anatomy that are often misdiagnosed are provided. The injuries reviewed represent a common and growing subset of pathologic processes about which all pediatric and musculoskeletal radiologists should be knowledgeable. Understanding physeal injury is especially important because missed diagnoses can lead to premature physeal closure and osteoarthritis. ^©RSNA, 2016.

Joint Fluid, Bone Marrow Edemalike Changes, and Ganglion Cysts in the Pediatric Wrist: Features That May Mimic Pathologic Abnormalities-Follow-Up of a Healthy Cohort

OBJECTIVE

The presence of findings at wrist MRI that may mimic disease is a diagnostic problem. The purpose of this study is to examine the occurrence of bone marrow changes resembling edema, joint fluid, and ganglion cysts over time, in a cohort of healthy children.

MATERIALS AND METHODS

Seventy-four of 89 healthy children included in a study of normal MRI findings of the wrists were reexamined after a period of 4 years, using the same 1.5-T MRI technique-namely, a coronal T1-weighted and a T2-weighted fat-saturated sequence. A history of handedness, diseases, and sports activity was noted.

RESULTS

Bone marrow edema or edemalike changes were seen in 29 of 74 (39.2%) wrists in 2013 as compared with 35 of 72 (48.6%) wrists in 2009 (p = 0.153), all in different locations. Changes were found in central parts of the bone, on both sides of a joint, or near bony depressions. Fifty percent of all subjects had at least one fluid pocket greater than or equal to 2 mm. The location was unchanged in 47% of the joints. In 24% of the individuals, at least one ganglion cyst was seen. Six ganglion cysts present on the first scan were not seen on the follow-up scan, and 11 new ganglion cysts had appeared.

CONCLUSION

Awareness of normal MRI appearances of the growing skeleton is crucial when interpreting MRI of children, and such findings must not be interpreted as pathologic abnormalities.

Running Injuries During Adolescence and Childhood

The popularity of running among young athletes has significantly increased over the past few decades. As the number of children who participate in running increases, so do the potential number of injuries to this group. Proper care of these athletes includes a thorough understanding of the unique physiology of the skeletally immature athlete and common injuries in this age group. Treatment should focus on athlete education, modification of training schedule, and correction of biomechanical deficits contributing to injury. Early identification and correction of these factors will allow a safe return to running sports.

"Children are not small adults": avoiding common pitfalls of normal developmental variants in pediatric imaging

Imaging of children is complicated with a vast array of normal variants, congenital or developmental disorders, and age-dependent differential considerations. We present imaging findings of several common anatomic variants as well as physiological and maturational processes that occur in children. We compare and contrast them with pathological entities so that the reader can successfully distinguish them when interpreting pediatric imaging examinations. The content has been accrued from the authors' collective experience at a tertiary-care pediatric hospital, teaching and consulting with radiology trainees and clinicians, as well as a comprehensive review of the literature, and is intended to represent a useful error prevention tool for radiologists interpreting pediatric studies.