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ABSTRACT: Background: Osteosarcoma is the most common primary bone tumor in children. While the humerus is the third most common anatomic location, it is the most common site for fractures. Our objective is to characterize magnetic resonance imaging (MRI) features of humerus osteosarcoma in children and with respect to risk of sustaining a pathologic fracture. Methods: Children with histologically confirmed humerus osteosarcoma, who underwent preoperative MRI (2008-2023) were included. Two radiologists retrospectively reviewed all MRIs to determine medullary (skip lesions and trans-epiphyseal tumor), joint, and extraosseous (muscle, neurovasculature, and lymphadenopathy) disease. Tumor volumes were measured at diagnosis and after neoadjuvant chemotherapy, and findings between those with and without fractures were compared. Results: This study included 25 children (10 boys, 15 girls; mean age: 12.9 ± 4.2 years), 9 (36%) with (6 at diagnosis, 3 during treatment) and 16 (64%) without fractures. Radiologists’ agreement on various MRI characteristics including bone, joint, muscle, and neurovascular involvement of humerus osteosarcoma ranged between 60 and 100%. The most common findings included trans-epiphyseal tumor (80%), involvement of the long head of the biceps tendon (76%), and axillary neurovasculature (72%). Although tumor volumes were smaller in patients with (104 cm3, interquartile range [IQR]: 68-116) than without fractures (136 cm3, IQR: 100-216), this difference did not reach significance (p = .07); no other findings differed between the groups (p > .05). At a median follow-up of 17 months (IQR: 7-55), 52% relapsed, but no significant association was found between relapse and fracture (p = .69). Conclusions: Over a third of the patients with humerus osteosarcoma had pathologic fractures in our study group, but these did not significantly associate with larger tumor size, specific MRI features, or increased risk for disease relapse. Key Concepts: (1) The most common MRI findings in children with humerus osteosarcoma were trans-epiphyseal disease, followed by extraosseous disease involving the long head of the biceps tendon and the axillary neurovasculature. (2) The lack of significant differences between fracture and nonfracture groups in terms of serum biomarkers, histologic subtype and treatment response, MRI findings and outcome suggest that these fractures may result from a combination of tumor-related and patient-specific factors, but do not significantly associate with increased risk for relapse. Level of Evidence: III, retrospective cohort study

Objective To assess the feasibility of T2 mapping for evaluating pediatric SIJ cartilage at 3 Tesla (T) magnetic resonance imaging (MRI). Methods Healthy control subjects and adolescents with sacroiliitis underwent a 3T MRI dedicated pelvic protocol that included a T2 mapping sequence consisting of multislice, multiecho acquisition. Healthy control subjects were prospectively recruited from our primary care practices as part of a larger imaging study, whereas adolescents with sacroiliitis were recruited specifically for this study. Regions of interest (ROIs) were hand‐drawn by a senior pediatric radiologist twice and a radiology fellow twice to calibrate and test reliability using the intraclass correlation coefficient (ICC). T2 relaxation time between control subjects and cases was compared using univariate linear regression. We tested the association of T2 relaxation time in adolescents with sacroiliitis with patient‐reported outcomes and the Spondyloarthritis Research Consortium of Canada sacroiliac joint (SIJ) inflammation and structural scores using Pearson correlation coefficients. Results Fourteen subjects were evaluable (six control subjects: median age 13.7 years [interquartile range (IQR): 12.2‐15.5], 67% male patients; eight cases: median age 17.4 years [IQR: 12.5‐20], 88% male patients]. Acquisition time for T2 mapping sequences was approximately 6 minutes, and segmenting the ROI for each SIJ took approximately 3 minutes. The intrarater and inter‐rater ICCs were 0.67 and 0.46, respectively, indicating good to fair reliability. There was a trend, albeit statistically insignificant, in longer median T2 relaxation time in cases (43.04 ms; IQR: 41.25‐49.76 ms) versus healthy control subjects (40.0 ms; IQR: 38.9‐48.6 ms). Although not statistically significant, cases with longer T2 relaxation time tended to occur with poorer patient‐reported outcomes. Correlations with the SIJ inflammation and structural lesion scores were weak. Conclusion T2 mapping of the SIJ cartilage in children was feasible and reliable. Larger controlled and longitudinal assessments are needed to assess the validity and utility of these measurements for routine clinical practice and trials.

Background: Discoid lateral meniscus (DLM) is the most common congenital abnormality of the meniscus. Tears are common; treatment is frequently not definitive, often requiring reoperation. Purpose: To report the clinical manifestations, physical characteristics, operative treatments and findings, complications, and reoperations of DLM in pediatric patients from multiple centers across North America. Study Design: Case series; Level of evidence, 4. Methods: Consecutive patients who underwent treatment for symptomatic DLM at 9 institutions between 2000 and 2020 were included. Patient data, presenting symptoms and signs, surgical findings, treatments rendered, and postoperative complications, including reoperation rates, were collected. Means with ranges and counts with proportions are reported for continuous and categorical variables, respectively, and comparisons were made using either the chi-square or Fisher exact test. Results: In total, 784 patients (867 knees) were included with a mean age at diagnosis of 12 years (range, 1-22 years) and a mean follow-up of 22.6 months (range, 0-154 months). Common preoperative symptoms were locking (33%) and snapping (30%). At surgery, tears in the DLM were present in 647 knees (594 patients [76%]); 95 knees (11%) had multiple tears; and in 140 knees, tears extended into >1 zone. Tears, when present, were more common within the posterior horn (41%) or body (34%) than the anterior horn (25%). Peripheral rim instability was reported in 241 knees (28%). Significantly more knees had instability posteriorly (15%; P =.0004) and anteriorly (9%; P =.0013) than along the body (3%). Tear type was most commonly complex (38%) or horizontal (34%). A total of 358 knees in 333 patients with tears (42% of all patients) underwent repair (55% of knees with tears). A total of 175 complications were reported, occurring in 139 knees in 134 patients (17%); 116 of these knees with complications (83%) had a single complication, while 23 (17%) had >1. Of the 784 patients, 105 (13%) underwent reoperation, undergoing 135 additional procedures related to their DLM. Of those, 60 (44%) were repeat arthroscopy and meniscal trim; 40 (30%), arthroscopy and meniscal repair; and 17 (13%), an articular cartilage procedure. Conclusion: Locking and snapping were common presenting symptoms. Over three-quarters of patients had meniscal tears, which were most often complex and located posteriorly. Seventeen percent of patients experienced complications, and a sixth of patients with complications had >1. Reoperation was typically for persistent symptoms or meniscal retear. [ABSTRACT FROM AUTHOR]

Growth and maturation occur in a predictable pattern throughout the body and within each individual bone. In the appendicular skeleton, endochondral ossification predominates in long bones and growth plates. The ends of these long bones are sites of relative weakness in the immature skeleton and prone to injury from acute insult and overuse. We present the normal histoanatomy and physiology of the growth plate complex, highlighting the unique contribution of each component and shared similarities between primary and secondary complexes. Components of the growth plate complex include the physis proper, subjacent vascularity within the growth cartilage, and the ossification front. The second section describes imaging considerations and features of normal and abnormal growth. Finally, we review the Salter-Harris classification for acute fractures and offer examples of characteristic overuse injury patterns involving the epiphyseal (proximal humerus and distal radius), apophyseal (medial epicondyle and tibial tubercle), and secondary growth plate complexes (medial femoral condyle and capitellar osteochondritis dissecans). This article provides a foundation and basic framework to better understand and anticipate potential complications and growth disturbances and to ensure optimal follow-up and early intervention when treatment can be less invasive. [ABSTRACT FROM AUTHOR]

The pediatric elbow is a complex joint that undergoes rapid growth and development. The normal anatomy of the elbow varies depending on the age of the patient, which can be challenging for imaging interpretation. This article reviews developmental variants and common pathologies of the pediatric elbow, with a focus on their radiologic features. Normal anatomy and development of the pediatric elbow are discussed, including the six ossification centers and elbow alignment. Congenital anomalies such as longitudinal deficiencies of the upper extremity are reviewed. Some common injuries that affect the elbow, such as supracondylar fracture, lateral condyle fracture, medial epicondyle avulsion, and radial head dislocation are also described. [ABSTRACT FROM AUTHOR]

During normal development, imaging findings in the immature knee joint may mimic pathology or indicate transient sites of weakness, prone to injury. This article reviews the development of the knee joint, age- and maturation-dependent imaging considerations, and various developmental variants that can be encountered, subdivided into those that involve the tibiofemoral and patellofemoral compartments, soft tissues, and osseous components. The tibiofemoral compartment section reviews the focal periphyseal edema zone (FOPE), ossification variants of the femoral condyles, distal femoral metaphyseal cortical irregularity from periosteal traction, and the metaphyseal subperiosteal stripe, which should be distinguished from pathologic mimickers such as endochondral ossification dysfunction, osteochondritis dissecans (OCD), fibroosseous lesion, periosteal and subcortical pathologies. The patellofemoral compartment section includes a review of partite patella, dorsolateral defect, variant trochlear morphology, and maturation-dependent sites of transient weakness that are prone to injury from repetitive overuse (Sinding-Larsen-Johansson syndrome and Osgood-Schlatter disease) and avulsion fractures (patellar sleeve and tibial tubercle avulsions). Finally, soft tissue (discoid lateral meniscus, meniscal flounce, anterior cruciate ligament variants) and osseous components (meniscal ossicle, fabella, and cyamella) are reviewed. [ABSTRACT FROM AUTHOR]

Year-round participation in youth sport that involves high levels of repetitive movement fosters an environment in which overuse injuries are likely to occur. Epiphyseal primary physeal stress injuries (PSIs), unique to skeletally immature athletes, are a particular concern, given their potential for growth disturbance. Initially observed in Little League baseball players, these injuries are now known to affect the long bones around the shoulder, elbow, wrist, hand, knee, ankle, and foot of skeletally immature athletes involved in a variety of sport activities. This article offers an epidemiological and radiologic perspective on the extent and distribution of epiphyseal PSIs in youth sport. We also review a novel framework for understanding the pathophysiologic mechanisms causing these injuries. This information is essential for the early identification of epiphyseal PSIs and devising preventive measures that can reduce a delayed diagnosis and long-term morbidity. Preventing and reducing injury to the epiphyseal growth plates is essential because impairment and dysfunction can result in lifelong morbidity and a risk of premature osteoarthritis. [ABSTRACT FROM AUTHOR]

Increase in youth sports participation, longer duration of play, and earlier starting points have increased the prevalence of acute and repetitive overuse musculoskeletal injuries. This rise in injury rates has led to increased efforts to better understand the susceptible sites of injury that are unique to the growing immature skeleton. Upper extremity injuries are currently the best studied, particularly those that occur among pediatric baseball players and gymnasts. The weak link in skeletally immature athletes is the growth plate complex that includes those injuries located at the epiphyseal and apophyseal primary physes and the peripherally located secondary physes. This article reviews the anatomy and function of these growth plate complexes, followed by a discussion of the pathophysiologic mechanisms, spectrum of imaging findings, and existing evidence-based guidelines for injury prevention and return to play. [ABSTRACT FROM AUTHOR]