Background: The use of bridge-enhanced anterior cruciate ligament (ACL) restoration (BEAR) procedures is on the rise. Yet, there is a paucity of literature describing the radiographic appearance of the ACL after this procedure. Purpose: To present the quantitative and qualitative postoperative changes in healing ACLs within the first 24 months after an ACL restoration procedure. Study Design: Case series; Level of evidence, 4. Methods: A total of 64 patients (64 knees, 19.4 ± 5 years, 57% women) underwent magnetic resonance imaging (MRI) of the knee 6, 12, and 24 months after ACL restoration surgery with an extracellular matrix scaffold as part of a randomized-controlled trial. The ACL sagittal elevation angle and tunnel positions, along with ACL volume, mean cross-sectional area (CSA), length, and normalized signal intensity (SI), were quantified from MRI. Patients were divided into quartiles based on SI at 24 months after surgery for inclusion in the qualitative analysis with an adapted framework for assessing tissue quality. Additional cases were selected for qualitative analysis based on clinical representations. Linear mixed modeling with Tukey post hoc corrections was used to analyze quantitative ACL healing parameters. Results: Tunnel positions were anatomic in 26.6% of femurs and 68.8% of tibias. The healing ACL sagittal elevation angle remained stable (<1° change between postoperative time points; P > .1) and was comparable with the contralateral native ACL (<2° difference between contralateral and BEAR at postoperative time points; P > .05) at all time points. The healing ACL volume and CSA decreased over time ( P < .01) but remained 20% (volume) and 15% (CSA) larger than the contralateral ACL at 24 months postoperatively (by 341 mm 3 volume and 6 mm 2 CSA; P < .001). The healing ACL length was constant over time (<1 mm change between postoperative time points; P > .1) and was 5% longer than the contralateral native ACL at final follow-up (by 1.8 mm; P = .027). The ACL SI decreased over time ( P < .001) and was 10% less than the contralateral ACL at 24 months (by 0.1 ± 0.3; P = .022). Seven relevant clinical scenarios were highlighted to show a spectrum of healing trajectories after ACL restoration surgery. Conclusion: The present study demonstrates that throughout 2 years of serial imaging after an ACL restoration procedure, the healing ACL becomes smaller cross-sectionally and more organized (lower normalized SI). Despite changes in the ACL size and ACL SI, the sagittal orientation remains unchanged and comparable with the contralateral native ACL. In the qualitative analysis, 7 distinct healing trajectories were identified. These data are important for interpreting postoperative imaging after the BEAR procedure, and for identifying that several healing trajectories exist after a restoration procedure. Further studies are warranted to identify patient-specific factors that may influence these trajectories. Registration: NCT02664545 (ClinicalTrials.gov identifier).

Pediatric bone lesions encompass a diverse spectrum of conditions, including benign neoplasms, cystic lesions, fibro-osseous lesions, and malignant tumors. This review highlights key diagnostic and management principles for commonly encountered non-sarcomatous lesions such as chondroblastoma, giant cell tumor, and aneurysmal bone cyst. Emphasis is placed on integrating clinical presentation, radiographic imaging, histopathological examination, and molecular diagnostics, such as H3.3 mutations and USP6 rearrangements, to refine differential diagnoses. A multidisciplinary approach is essential for optimizing outcomes in pediatric bone tumor care.

Upper extremity radiographic exams have long been considered as a single category with one simplified low-dose estimate, despite covering a variety of body parts. There are limited tools currently available for the simulation/calculation of radiation dose from upper extremity exams. This study aims to evaluate radiation dose (in terms of effective dose and organ doses) from various types of pediatric upper extremity radiographic exams as performed at a large tertiary care children’s hospital using a new set of hybrid computational phantoms that incorporate the anatomy of upper extremities and cover varied patient sexes and ages. Technical acquisition parameters were collected for upper extremity exams at our institution according to the age-based categories as defined by clinical protocols. A relationship was established between radiographic acquisition parameters and dose-area product for each category using direct measurements. A new set of computational phantoms with posed upper extremities was introduced and used to run Monte Carlo simulations of patient effective dose and organ doses for all relevant projections. The calculated effective dose to upper extremities was found to range from 0.01 µSv for a hand/finger radiograph of a 3–6-year-old to 1.13 µSv for a humerus radiograph of a 1–3-year-old. The four tissues with the highest organ dose from all projections were the same: skin, muscle, endosteum, and red marrow. Doses to these organs as well as breast and thyroid were reported, and conversion coefficients to estimate effective dose and organ doses from dose-area product were calculated. Simulations of pediatric upper extremity radiographs using a set of newly-modified computational phantoms present a wide range of effective and organ doses. The doses reported in this study can be adapted to site-specific practices for rough estimations.

Background:Lyme arthritis is a common manifestation of late-stage Lyme disease in pediatric and adolescent patients. Patients with Lyme arthritis typically present with atraumatic knee effusion and may undergo magnetic resonance imaging (MRI) to aid in diagnosis. The incidence of meniscal pathology on MRI in association with Lyme arthritis is unknown. This study aims to evaluate the incidence of meniscal pathology on MRI in young patients with Lyme arthritis. Methods:Patients (<18 years old) presenting with a unilateral knee effusion from 2009 to 2019 with a positive Lyme antibody serologic test, MRI within 2 weeks of the positive test, and ultimate diagnosis of Lyme arthritis were included in the study. MRI, which was performed to distinguish Lyme arthritis from other causes of knee effusion, underwent analysis by a pediatric musculoskeletal radiologist. Meniscal signal abnormality was graded as follows: grade 1 = globular, grade 2 = linear nonsurfacing, and grade 3 = surfacing tear. Results:Eighty-seven patients (10.6 ± 3.9 years, 71.3% male, 67.8% White) were included. Fourteen (16%) patients had meniscal changes (grade 1: n = 4 [5%]; grade 2: n = 3 [3%]; grade 3: n = 7 [8%]). Thirteen of the 14 patients (93%) with meniscal changes on MRI were treated only with oral antibiotics, with resolution of knee symptoms and return to sports, whereas 1 patient (7%) underwent arthroscopic partial meniscectomy. Conclusions:Of the 87 pediatric patients with serologically confirmed Lyme arthritis and MRI of their affected knee, 16% had a coexistent meniscal abnormality on MRI, but only 1 patient overall required surgical treatment related to the meniscus. Physicians should be aware of potential MRI meniscal changes in pediatric and adolescent patients who present with symptomatic knee effusion because of Lyme arthritis. Future research to evaluate the physiologic effects of Lyme arthritis on meniscal tissue is needed. Level of Evidence:Level IV Case Series. See Instructions for Authors for a complete description of levels of evidence.

Background:Bridge-enhanced anterior cruciate ligament restoration (BEAR) combines suture repair of the anterior cruciate ligament (ACL) with an extracellular matrix implant plus autologous blood to facilitate native ACL healing. Purpose/Hypothesis:The purpose of this study was to compare the 6-year follow-up outcomes of patients who underwent the BEAR procedure with those of a nonrandomized concurrent control group receiving autograft ACL reconstruction (ACLR) in the first-in-human safety study of the BEAR implant (BEAR I trial). Based on the 2-year results, it was hypothesized that isometric hamstring strength after the BEAR procedure would be greater than that after ACLR and that there would be no other differences in outcomes at 6 years. Study Design:Cohort study, Level of evidence, 2. Methods:Ten patients underwent BEAR and 10 received ACLR with a 4-stranded hamstring autograft. Outcomes assessed included the record of subsequent surgeries, the International Knee Documentation Committee (IKDC) Subjective Knee Score, IKDC physical examination grade, the Knee injury and Osteoarthritis Outcome Score, instrumented knee laxity, functional outcomes (ie, muscle strength assessments and hop testing), and qualitative magnetic resonance imaging assessment. Comparisons between treatments were based on computations of the mean differences and the associated 95% CIs. Results:One patient in the BEAR group and 3 patients in the ACLR group were lost to follow-up. In the period between 2 and 6 years, 1 patient in each group underwent revision surgery. There were no differences between groups at the 6-year follow-up in any of the outcome measures except for isometric hamstring strength, which was approximately equal to that of the contralateral knee in the BEAR group and <44% of that in the contralateral knee in the ACLR group (P < .01). Conclusion:This preliminary study suggests that the outcomes of BEAR and ACLR with a hamstring tendon graft may be similar at the 6-year follow-up and warrants investigation of the BEAR procedure in a larger cohort of patients.

Background:The classic metaphyseal lesion (CML) is a distinctive fracture highly specific to infant abuse. To increase the size and diversity of the training CML database for automated deep-learning detection of this fracture, we developed a mask conditional diffusion model (MaC-DM) to generate synthetic images with and without CMLs. Purpose:To objectively and subjectively assess the synthetic radiographic images with and without CMLs generated by MaC-DM. Materials and Methods:For retrospective testing, we randomly chose 100 real images (50 normals and 50 with CMLs; 39 infants, male = 22, female = 17; mean age = 4.1 months; SD = 3.1 months) from an existing distal tibia dataset (177 normal, 73 with CMLs), and generated 100 synthetic distal tibia images via MaC-DM (50 normals and 50 with CMLs). These test images were shown to 3 blinded radiologists. In the first session, radiologists determined if the images were normal or had CMLs. In the second session, they determined if the images were real or synthetic. We analyzed the radiologists' interpretations and employed t-distributed stochastic neighbor embedding technique to analyze the data distribution of the test images. Results:When presented with the 200 images (100 synthetic, 100 with CMLs), radiologists reliably and accurately diagnosed CMLs (kappa = 0.90, 95% CI = [0.88-0.92]; accuracy = 92%, 95% CI = [89-97]). However, they were inaccurate in differentiating between real and synthetic images (kappa = 0.05, 95% CI = [0.03-0.07]; accuracy = 53%, 95% CI = [49-59]). The t-distributed stochastic neighbor embedding analysis showed substantial differences in the data distribution between normal images and those with CMLs (area under the curve = 0.996, 95% CI = [0.992-1.000], P < .01), but minor differences between real and synthetic images (area under the curve = 0.566, 95% CI = [0.486-0.647], P = .11). Conclusion:Radiologists accurately diagnosed images with distal tibial CMLs but were unable to distinguish real from synthetically generated ones, indicating that our generative model could synthesize realistic images. Thus, MaC-DM holds promise as an effective strategy for data augmentation in training machine-learning models for diagnosis of distal tibial CMLs.

Normalized signal intensity (SI) obtained from magnetic resonance imaging (MRI) has been used to track anterior cruciate ligament (ACL) postoperative remodeling. We aimed to assess the effect of MRI sequence (PD: proton density-weighted; T2: T2-weighted; CISS: constructive interference in steady state) on postoperative changes in healing ACLs/grafts. We hypothesized that CISS is better at detecting longitudinal SI and texture changes of the healing ACL/graft compared to the common clinical sequences (PD and T2). MR images of patients who underwent ACL surgery were evaluated and separated into groups based on surgical procedure (Bridge-Enhanced ACL Repair (BEAR; n = 50) versus ACL reconstruction (ACLR; n = 24)). CISS images showed decreasing SI across all timepoints in both the BEAR and ACLR groups (p < 0.01), PD and T2 images showed decreasing SI in the 6-to-12- and 12-to-24-month postoperative timeframes in the BEAR group (p < 0.02), and PD images additionally showed decreasing SI between 6- and 24-months postoperation in the ACLR group (p = 0.02). CISS images showed texture changes in both the BEAR and ACLR groups, showing increases in energy and decreases in entropy in the 6-to-12- and 6-to-24-month postoperative timeframes in the BEAR group (p < $\lt $ 0.04), and increases in energy, decreases in entropy, and increases in homogeneity between 6 and 24 months postoperation in the ACLR group (p < 0.04). PD images showed increases in energy and decreases in entropy between 6- and 24-months postoperation in the ACLR group (p < 0.008). Finally, CISS was estimated to require a smaller sample size than PD and T2 to detect SI differences related to postoperative remodeling.

Smaller anterior cruciate ligament (ACL) size in females has been hypothesized to be a key contributor to a higher incidence of ACL tears in that population, as a lower cross-sectional area (CSA) directly corresponds to a larger stress on the ligament for a given load. Prior studies have used a mid-length CSA measurement to quantify ACL size. In this study, we used magnetic resonance imaging to quantify the CSA along the entire length of the intact ACL. We hypothesized that changes in the ACL CSA along its length would have different patterns in males and females. We also hypothesized that changes in ACL CSA along its length would be associated with body size or knee size with different associations in females and males. MR images of contralateral ACL-intact knees of 108 patients (62 females, 13-35 years) undergoing ACL surgery were used to measure the CSA along the ACL length, using a custom program. For both females and males, the largest CSA was located at 37%-39% of ACL length from the tibial insertion. Compared to females, males had a significantly larger CSA only within the distal 41% of the ACL (p < 0.001). ACL CSA was associated with patient height and weight in males (r > 0.3; p < 0.05), whereas it was associated with intercondylar notch width in females (r > 0.3; p < 0.05). These findings highlight the importance of standardizing the location of measurement of ACL CSA.

Primary lymphoma of bone is an uncommon non-Hodgkin lymphoma. Magnetic resonance imaging (MRI) features of primary lymphoma of bone in children are not well described. To identify typical MRI characteristics of pediatric primary lymphoma of bone at diagnosis and following treatment. Two pediatric radiologists retrospectively reviewed all imaging studies of 10 patients with biopsy-proven primary lymphoma of bone at presentation and after treatment. Anatomic location, number of sites, location within bone (epiphyseal, metaphyseal, diaphyseal), T1-weighted imaging margins, soft tissue mass, T2-weighted imaging appearance and enhancement pattern (homogeneous, heterogeneous, infarct-like), soft tissue edema, cortical disruption, and regional lymph nodes as seen on MRI as well as radiographic and positron emission tomography (PET) findings were recorded. Pathologic results, treatment plans, and outcomes at follow-up as detailed in the medical record were tabulated. Of 10 patients, age at diagnosis 8–17 years, median 15 years, 4 (40

Fracture dating from skeletal surveys is crucial in the diagnosis and investigation of infant abuse. However, this task is challenging because of the subjective nature of the radiologic interpretation and the lack of ground truth. Researchers have used birth-related clavicle fractures as a surrogate to study the radiographic pattern of healing; however, they did not elucidate the accuracy performance of the radiologists in dating fractures. To determine the accuracy of radiologists in dating birth-related clavicle fractures and compare their performance to that achieved by computer algorithm. We used a previously assembled birth-related clavicle fracture database consisting of 416 anteroposterior clavicle radiographs as the study cohort. The average and standard deviation of the fracture age within this database were 24 days and 18 days, respectively. Three blinded radiologists independently estimated the ages of the clavicle fractures depicted in the radiographs within the database. We compared these estimation results to those made by a recently published deep-learning (DL) model conducted with the identical infant cohort. We calculated standard error metrics to compare the accuracy performances of the radiologists and the computer model. The intra- and inter-reader agreements of the fracture age estimates by the radiologists were moderate to good. The radiologists estimated the fracture ages with a mean absolute error (MAE) of 6.1–7.1 days, and standard deviation of the absolute error of 6.3–8.3 days. The accuracy performances of the three radiologists were not significantly different from one another. In comparison, the DL model estimated the age of clavicle fractures with an MAE of 4.2 days, significantly lower than all of the radiologists (P < 0.001). Three experienced pediatric radiologists dated clavicular fractures with moderate–good intra- and inter-reader agreements. The correlations between the radiologists’ estimates and the ground truth were moderate to good. The fracture ages assigned by the DL model showed superior correlation with the ground truth compared to radiologists’ dating estimates.

Anterior cruciate ligament (ACL) injuries are a common cause of soft tissue injuries in young active individuals, leading to a significant risk of premature joint degeneration. Postoperative management of such injuries, in particular returning patients to athletic activities, is a challenge with immediate and long-term implications including the risk of subsequent injury. In this study, we present LigaNET, a multi-modal deep learning pipeline that predicts the risk of subsequent ACL injury following surgical treatment. Postoperative MRIs (n=1,762) obtained longitudinally between 3 to 24 months after ACL surgery from a cohort of 159 patients along with 11 non-imaging outcomes were used to train and test: 1) a 3D CNN to predict subsequent ACL injury from segmented ACLs, 2) a 3D CNN to predict injury from the whole MRI, 3) a logistic regression classifier predict injury from non-imaging data, and 4) a multi-modal pipeline by fusing the predictions of each classifier. The CNN using the segmented ACL achieved an accuracy of 77.6% and AUROC of 0.84, which was significantly better than the CNN using the whole knee MRI (accuracy: 66.6%, AUROC: 0.70; P<.001) and the non-imaging classifier (accuracy: 70.1%, AUROC: 0.75; P=.039). The fusion of all three classifiers resulted in highest classification performance (accuracy: 80.6%, AUROC: 0.89), which was significantly better than each individual classifier (P<.001). The developed multi-modal approach had similar performance in predicting the risk of subsequent ACL injury from any of the imaging sequences (P>.10). Our results demonstrate that a deep learning approach can achieve high performance in identifying patients at high risk of subsequent ACL injury after surgery and may be used in clinical decision making to improve postoperative management (e.g., safe return to sports) of ACL injured patients.

Non-invasive methods to document healing anterior cruciate ligament (ACL) structural properties could potentially identify patients at risk for revision surgery. The objective was to evaluate machine learning models to predict ACL failure load from magnetic resonance images (MRI) and to determine if those predictions were related to revision surgery incidence. It was hypothesized that the optimal model would demonstrate a lower mean absolute error (MAE) than the benchmark linear regression model, and that patients with a lower estimated failure load would have higher revision incidence 2 years post-surgery. Support vector machine, random forest, AdaBoost, XGBoost, and linear regression models were trained using MRI T2* relaxometry and ACL tensile testing data from minipigs (n = 65). The lowest MAE model was used to estimate ACL failure load for surgical patients at 9 months post-surgery (n = 46) and dichotomized into low and high score groups via Youden's J statistic to compare revision incidence. Significance was set at alpha = 0.05. The random forest model decreased the failure load MAE by 55% (Wilcoxon signed-rank test: p = 0.01) versus the benchmark. The low score group had a higher revision incidence (21% vs. 5%; Chi-square test: p = 0.09). ACL structural property estimates via MRI may provide a biomarker for clinical decision making.

Background: Quantitative magnetic resonance imaging (qMRI) methods were developed to establish the integrity of healing anterior cruciate ligaments (ACLs) and grafts. Whether qMRI variables predict risk of reinjury is unknown. Purpose: To determine if qMRI measures at 6 to 9 months after bridge-enhanced ACL restoration (BEAR) can predict the risk of revision surgery within 2 years of the index procedure. Study Design: Cohort study; Level of evidence, 2. Methods: Originally, 124 patients underwent ACL restoration as part of the BEAR I, BEAR II, and BEAR III prospective trials and had consented to undergo an MRI of the surgical knee 6 to 9 months after surgery. Only 1 participant was lost to follow-up, and 4 did not undergo MRI, leaving a total of 119 patients for this study. qMRI techniques were used to determine the mean cross-sectional area; normalized signal intensity; and a qMRI-based predicted failure load, which was calculated using a prespecified equation based on cross-sectional area and normalized signal intensity. Patient-reported outcomes (International Knee Documentation Committee subjective score), clinical measures (hamstring strength, quadriceps strength, and side-to-side knee laxity), and functional outcomes (single-leg hop) were also measured at 6 to 9 months after surgery. Univariate and multivariable analyses were performed to determine the odds ratios (ORs) for revision surgery based on the qMRI and non-imaging variables. Patient age and medial posterior tibial slope values were included as covariates. Results: In total, 119 patients (97%), with a median age of 17.6 years, underwent MRI between 6 and 9 months postoperatively. Sixteen of 119 patients (13%) required revision ACL surgery. In univariate analyses, higher International Knee Documentation Committee subjective score at 6 to 9 months postoperatively (OR = 1.66 per 10-point increase; P = .035) and lower qMRI-based predicted failure load (OR = 0.66 per 100-N increase; P = .014) were associated with increased risk of revision surgery. In the multivariable model, when adjusted for age and posterior tibial slope, the qMRI-based predicted failure load was the only significant predictor of revision surgery (OR = 0.71 per 100 N; P = .044). Conclusion: Quantitative MRI-based predicted failure load of the healing ACL was a significant predictor of the risk of revision within 2 years after BEAR surgery. The current findings highlight the potential utility of early qMRI in the postoperative management of patients undergoing the BEAR procedure.

Patients with Crohn's disease often have low bone mineral density and an increased risk of osteoporosis. Although decreased bone formation can be seen at diagnosis, the underlying pathophysiology of suboptimal bone accrual remains poorly understood. We sought to evaluate a novel mechanism affecting osteogenesis in patients with Crohn's disease. In this case series, we evaluated bone marrow composition at the distal femur and proximal tibia of the left knee measured via magnetic resonance (MR) spectroscopy and relaxometry in five adolescents with the diagnosis of Crohn's disease. The subjects were enrolled prospectively between 2011 and 2013 at Boston Children's Hospital. Additional clinical information, including DXA scans to evaluate bone mineral density and body composition, and Crohn's disease history, such as glucocorticoid use and disease duration, were assessed. Healthy adolescents have persistent hematopoietic marrow with only 40 to 50 % fat in the long bone metaphyses. The current participants with Crohn's disease had increased marrow adiposity, with a mean fat fraction of 67.8 %. There appeared to be a trend towards higher fat fraction with shorter disease duration, while participants with the longest disease duration had the lowest fat fraction. Participants also had decreased bone density, increased fat mass, and lower lean mass, as assessed by DXA and compared to pediatric reference data. Our MRI results demonstrate increased marrow adiposity in children with Crohn's disease, especially early in the course of the disease. DXA may better demonstrate longer-term effects on bone. Additional studies are needed to evaluate bone marrow composition in these patients and to elucidate further the inverse relationship between marrow adipocytes and osteogenesis, as well as the relationship between bone marrow adiposity and body composition.

Background: Anterior cruciate ligament (ACL) revision surgery is challenging for both patients and surgeons. Understanding the risk factors for failure after bridge-enhanced ACL restoration (BEAR) may help with patient selection for ACL restoration versus ACL reconstruction. Purpose: To identify the preoperative risk factors for ACL revision surgery within the first 2 years after BEAR. Study Design: Case-control study; Level of evidence, 3. Methods: Data from the prospective BEAR I, II, and III trials were used to determine the preoperative risk factors for ACL revision surgery. All patients with a complete ACL tear (aged 13-47 years, depending on the trial), who met all other inclusion/exclusion criteria and underwent a primary BEAR procedure within 30 to 50 days from the injury (dependent on the trial), were included. Demographic data (age, sex, body mass index), baseline patient-reported outcomes (International Knee Documentation Committee [IKDC] subjective score, Marx activity score), preoperative imaging results (ACL stump length, notch size, tibial slope), and intraoperative findings (knee hyperextension, meniscal status) were evaluated to determine their contribution to the risk of ipsilateral ACL revision surgery. Results: A total of 123 patients, with a median age of 17.6 years (interquartile range, 16-23 years), including 67 (54%) female patients, met study criteria. Overall, 18 (15%) patients required ACL revision surgery in the first 2 years after the BEAR procedure. On bivariate analyses, younger age ( P = .011), having a contact injury at the time of the initial tear ( P = .048), and increased medial tibial slope (MTS; P = .029) were associated with a higher risk of ipsilateral revision surgery. Multivariable logistic regression analyses identified 2 independent predictors of revision: patient age and MTS. The odds of ipsilateral revision surgery were decreased by 32% for each 1-year increase in age (odds ratio, 0.684 [95% CI, 0.517-0.905]; P = .008) and increased by 28% for each 1° increase in MTS (odds ratio, 1.280 [95% CI, 1.024-1.601]; P = .030). Sex, baseline IKDC or Marx score, knee hyperextension, and meniscal status were not significant predictors of revision. Conclusion: Younger age and higher MTS were predictors of ipsilateral ACL revision surgery after the BEAR procedure. Younger patients with higher tibial slopes should be aware of the increased risk for revision surgery when deciding to undergo ACL restoration.

Pubertal suppression with gonadotropin-releasing hormone (GnRH) agonists in transgender and gender non-conforming (TGNC) youth may affect acquisition of peak bone mass. Bone marrow adipose tissue (BMAT) has an inverse relationship with bone mineral density (BMD). To evaluate the effect of pubertal suppression on BMAT, in this pilot study we prospectively studied TGNC youth undergoing pubertal suppression and cisgender control participants with similar pubertal status over a 12-month period. BMD was measured by dual-energy X-ray absorptiometry and peripheral quantitative computed tomography. Magnetic Resonance T1 relaxometry (T1-R) and spectroscopy (MRS) were performed to quantify BMAT at the distal femur. We compared the change in BMD, T1-R values, and MRS lipid indices between the two groups. Six TGNC (two assigned female and four assigned male at birth) and three female control participants (mean age 10.9 and 11.7 years, respectively) were enrolled. The mean lumbar spine BMD Z-score declined by 0.29 in the TGNC group, but increased by 0.48 in controls (between-group difference 0.77, 95% CI: 0.05, 1.45). Similar findings were observed with the change in trabecular volumetric BMD at the 3% tibia site (-4.1% in TGNC, +3.2% in controls, between-group difference 7.3%, 95% CI: 0.5%-14%). Distal femur T1 values declined (indicative of increased BMAT) by 7.9% in the TGNC group, but increased by 2.1% in controls (between-group difference 10%, 95% CI: -12.7%, 32.6%). Marrow lipid fraction by MRS increased by 8.4% in the TGNC group, but declined by 0.1% in controls (between-group difference 8.5%, 95% CI: -50.2%, 33.0%). In conclusion, we observed lower bone mass acquisition and greater increases in BMAT indices by MRI and MRS in TGNC youth after 12 months of GnRH agonists compared with control participants. Early changes in BMAT may underlie an alteration in bone mass acquisition with pubertal suppression, including alterations in mesenchymal stem cells within marrow.

Background:The cross-sectional area (CSA) of the anterior cruciate ligament (ACL) and reconstructed graft has direct implications on its strength and knee function. Little is known regarding how the CSA changes along the ligament length and how those changes vary between treated and native ligaments over time. Hypothesis:It was hypothesized that (1) the CSA of reconstructed ACLs and restored ACLs via bridge-enhanced ACL restoration (BEAR) is heterogeneous along the length. (2) Differences in CSA between treated and native ACLs decrease over time. (3) CSA of the surgically treated ACLs is correlated significantly with body size (ie, height, weight, body mass index) and knee size (ie, bicondylar and notch width). Study Design:Cohort study; Level of evidence, 2. Methods:Magnetic resonance imaging scans of treated and contralateral knees of 98 patients (n = 33 ACL reconstruction, 65 BEAR) at 6, 12, and 24 months post-operation were used to measure the ligament CSA at 1% increments along the ACL length (tibial insertion, 0%; femoral insertion, 100%). Statistical parametric mapping was used to evaluate the differences in CSA between 6 and 24 months. Correlations between body and knee size and treated ligament CSA along its length were also assessed. Results:Hamstring autografts had larger CSAs than native ACLs at all time points (P < .001), with region of difference decreasing from proximal 95% of length (6 months) to proximal 77% of length (24 months). Restored ACLs had larger CSAs than native ACLs at 6 and 12 months, with larger than native CSA only along a small midsubstance region at 24 months (P < .001). Graft CSA was correlated significantly with weight (6 and 12 months), bicondylar width (all time points), and notch width (24 months). Restored ACL CSA was significantly correlated with bicondylar width (6 months) and notch width (6 and 12 months). Conclusion:Surgically treated ACLs remodel continuously within the first 2 years after surgery, leading to ligaments/grafts with heterogeneous CSAs along the length, similar to the native ACL. While reconstructed ACLs remained significantly larger, the restored ACL had a CSA profile comparable with that of the contralateral native ACL. In addition to size and morphology differences, there were fundamental differences in factors contributing to CSA profile between the ACL reconstruction and BEAR procedures. Registration:NCT02664545 (ClinicalTrials.gov identifier).

Background: Lyme disease is the most prevalent tick-borne illness in the United States, especially endemic in the Northeast and Upper Midwest. Distinguishing Lyme arthritis (LA), the most common manifestation of the disease in children, from septic arthritis (SA) can be challenging because of overlap in clinical presentations. This study examined the role of magnetic resonance imaging (MRI) as an adjunct to clinical and laboratory features used to differentiate between LA and SA in children and adolescents. Methods: The medical records and MRI scans of children who presented between 2009 and 2019 with an acute knee effusion ultimately diagnosed as LA or SA were retrospectively reviewed. Data collection included clinical information on the modified Kocher criteria (weight-bearing, fever, blood serology including white blood-cell [WBC] count, C-reactive protein [CRP], and erythrocyte sedimentation rate [ESR]), MRI findings, and serology confirmation of LA or bacterial SA. A total of 87 cases of confirmed LA and 9 cases of SA were identified. Results: The 2 cohorts had substantial clinical overlap with regard to the ability to bear weight, fever, and joint aspirate WBC count. Differences between the 2 groups in several MRI characteristics, specifically vastus lateralis myositis, subcutaneous edema, and lymphadenopathy, were significant. A multivariate analysis demonstrated that weight-bearing, CRP of <3 mg/L, absence of subcutaneous edema, myositis of multiple muscles including the vastus lateralis, and lymphadenopathy were predictive of LA. Conclusions: LA should be strongly suspected in endemic areas of the United States when children present with a knee effusion. The addition of MRI criteria to clinical and laboratory findings significantly improved the predictive value for identifying LA. Level of Evidence: Diagnostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Background:Lyme disease is the most prevalent tick-borne illness in the United States, especially endemic in the Northeast and Upper Midwest. Distinguishing Lyme arthritis (LA), the most common manifestation of the disease in children, from septic arthritis (SA) can be challenging because of overlap in clinical presentations. This study examined the role of magnetic resonance imaging (MRI) as an adjunct to clinical and laboratory features used to differentiate between LA and SA in children and adolescents. Methods:The medical records and MRI scans of children who presented between 2009 and 2019 with an acute knee effusion ultimately diagnosed as LA or SA were retrospectively reviewed. Data collection included clinical information on the modified Kocher criteria (weight-bearing, fever, blood serology including white blood-cell [WBC] count, C-reactive protein [CRP], and erythrocyte sedimentation rate [ESR]), MRI findings, and serology confirmation of LA or bacterial SA. A total of 87 cases of confirmed LA and 9 cases of SA were identified. Results:The 2 cohorts had substantial clinical overlap with regard to the ability to bear weight, fever, and joint aspirate WBC count. Differences between the 2 groups in several MRI characteristics, specifically vastus lateralis myositis, subcutaneous edema, and lymphadenopathy, were significant. A multivariate analysis demonstrated that weight-bearing, CRP of < 3 mg/L, absence of subcutaneous edema, myositis of multiple muscles including the vastus lateralis, and lymphadenopathy were predictive of LA. Conclusions:LA should be strongly suspected in endemic areas of the United States when children present with a knee effusion. The addition of MRI criteria to clinical and laboratory findings significantly improved the predictive value for identifying LA. Level of Evidence:Diagnostic Level III. See Instructions for Authors for a complete description of levels of evidence.