Forensic age assessment of the knee: proposal of a new classification system using two-dimensional ultrasound volumes and comparison to MRI

Objectives To assess epiphyseal growth plate closure of the knee for forensic age estimation using an ultrasound (US)-based method and to compare the findings with MRI. Methods Thirty-three healthy male individuals (age, 14.4–19.3 years) were prospectively evaluated for epiphyseal growth plate closure of the right knee by recordings of two-dimensional US volumes and a high-resolution T1-weighted MRI sequence. The degree of epiphyseal growth plate closure was rated independently by two readers for each method using a modality specific three-point scale that differentiates between an open physis (S1), a partially closed physis (S2), and a closed physis (S3). Results The inter-rater agreement was high for the US (Cohen’s kappa (CK): femur 95.2%, tibia 81.3%, fibula 86.3%) and the MRI method (CK: femur 70.2%, tibia 90.8%, fibula 79.8%). The degree of growth plate closure associated positively with advancing age. The US system showed a clearer separation of median ages with lower overlap than the MRI system. Open growth plates on minors (< S3 on femur and tibia) were identified by US with higher sensitivity (1.0 vs. 0.7) and slightly lower specificity (0.7 vs. 0.85) compared with MRI. The examination time was substantially shorter on US than on MRI (2.65 ± 0.91 min vs. 24.72 ± 2.72 min; p < 0.001). Conclusions The US method for evaluation of growth plate closure of the knee can reliably assign male individuals to different ossification stages and identifies minors with high accuracy. More studies with larger numbers are needed to further evaluate this method. Key Points • US is feasible to determine the degree of epiphyseal growth plate closure of the knee, shows a high degree of reliability, and is comparable to MRI. • US of the knee can detect open growth plates on male minors with high accuracy. • US of the knee may be used as a fast, non-invasive imaging tool for forensic age estimation to identify male minors.

No growth disturbance after trochleoplasty for recurrent patellar dislocation in adolescents with open growth plates

Aims and Objectives: Trochlear dysplasia is the most important risk factor to patellofemoral instability in adolescents, therefore trochleoplasty to reshape the trochlear groove is the treatment of choice in patients with severe trochlear dysplasia. However, in the presence of open growth plates there is a potential risk of injury of the distal femoral growth plate and subsequent growth disturbance. Therefore, most authors do not recommend trochleoplasty in skeletally immature patients. The effect of trochleoplasty on femoral growth when performed before closure of the distal femoral physis remains unclear. The hypothesis of the study was, that In patients with open growth plates and an expected growth of less than two years trochleoplasty does not cause growth disturbance of the distal femur. Materials and Methods: 18 consecutive adolescents (18 knees) with open physes and severe trochlear dysplasia underwent trochleoplasty. Pre- and postoperative radiographic examination included AP and lateral views to assess leg axis and patella alta. Preoperatively a radiograph of the left hand was performed to measure skeletal age. MRI was performed to evaluate trochlear dysplasia and tibial tubercle-trochlear groove (TT-TG) distance. Evaluation included pre- and postoperative physical examination with evaluation of leg length and leg axis, Kujala score, Activity Rating Scale (ARS) and Tegner activity score. Results: The average age at the time of operation was 12.6 y (range, 12.2 - 13.3) in girls and 14.5 y (14.0 - 15.4) in boys. The average follow-up after operation was 2.3 years after surgery (range, 2.0 - 3.0 years). At follow-up in all patients the growth plates of the knee were closed. Impairment of growth of the distal femur was neither found clinically nor radiographically. No recurrent dislocation occurred. The median Kujala score and median VAS showed significant improvement (p < 0.01). The activity level according to the Tegner activity score did not change statistically significant. Conclusion: In this study, trochleoplasty as a treatment for patellofemoral instability in patients with open physes and an expected growth of not more than two years showed good clinical results without redislocation and no growth disturbance. Therefore, in selected adolescent patients with severe trochlear dysplasia trochleoplasty can be safely performed up to two years before the projected end of growth.

CNN-based radiographic acute tibial fracture detection in the setting of open growth plates

Pediatric tibial fractures are commonly diagnosed by radiographs and constitute one of the common tasks performed by pediatric radiologists. Here, we assess the performance of a convolutional neural network for the detection of acute tibial fractures trained with a limited number of cases in skeletally immature patients. This retrospective study was performed on radiology reports manually classified as normal or tibial fracture. Classified images of orthopaedic implants, casting, and images including other pathology were excluded. The remaining cases constituted 516 studies containing 2118 radiographs. These radiographs were truncated to include a limited investigated field of view which included the distal third of the leg, inclusive of the distal physis. After exclusions, the culled dataset was randomly divided into a training set containing 784 radiographs, a validation set containing 98 radiographs, and a test set 98 radiographs. We used a modified transfer learning approach based on the Xception architecture with additional fully convoluted reasoning and drop-out layers. Of 49 distal Tibial fractures, two were misdiagnosed as normal. Of 49 normal exams, none were misdiagnosed. This led to model accuracy of 97.9%, sensitivity 95.9%, and specificity 100%, comparable to or better than human radiologists. In no instances were normal physes or normal developmental epiphyseal fragmentation of the tibial tuberosity or medial malleolus misclassified as a fracture. We report an efficient method to use a pre-trained network and adapt it to a medical classification task using only a small number of radiographs dedicated to precise anatomical location.

No Growth Disturbance After Trochleoplasty for Recurrent Patellar Dislocation in Adolescents With Open Growth Plates

Background: Trochlear dysplasia is the most important risk factor for patellofemoral instability among adolescents; therefore, trochleoplasty to reshape the trochlear groove is the treatment of choice for patients with high-grade trochlear dysplasia. However, in the presence of open growth plates, there is a potential risk of injury to the distal femoral growth plate and subsequent growth disturbance. As such, most authors do not recommend trochleoplasty for skeletally immature patients. The effect of trochleoplasty on femoral growth when performed before closure of the distal femoral physis remains unclear. Hypothesis: For patients with open growth plates and an expected growth <2 years, trochleoplasty does not cause growth disturbance of the distal femur. Study Design: Case series; Level of evidence, 4. Methods: Eighteen consecutive adolescents (18 knees) with open physes and severe trochlear dysplasia underwent thin flap trochleoplasty. Pre- and postoperative radiographic examination included anteroposterior and lateral views to assess leg axis and patella alta. A preoperative radiograph of the left hand was performed to measure skeletal age. Magnetic resonance imaging was performed to evaluate trochlear dysplasia and tibial tubercle–trochlear groove distance. Evaluation included pre- and postoperative physical examination with evaluation of leg length and leg axis, Kujala score, and Tegner activity score. Results: The median age at the time of operation was 12.6 years (range, 12.2-13.3 years) for girls and 14.5 years (14.0-15.4 years) for boys. The mean follow-up after operation was 2.3 years after surgery (range, 2.0-3.0 years). At follow-up for all patients, the growth plates of the knee were closed. Impairment of growth of the distal femur was found neither clinically nor radiographically. No recurrent dislocation occurred. The median Kujala score improved significantly from 67 (range, 54-75) preoperatively to 89.5 (range, 78-96) at follow-up ( P < .01). The median visual analog scale showed significant pre- to postoperative improvement from 5 (range, 3-7) to 1 (range, 0-3) ( P < .01). The activity level according to the Tegner activity score did not change significantly. Conclusion: In this study, trochleoplasty as a treatment for patellofemoral instability of patients with open physes and an expected growth of not more than 2 years showed good clinical results without redislocation and with no growth disturbance. Therefore, for selected adolescent patients with high-grade trochlear dysplasia, trochleoplasty can be safely performed up to 2 years before the projected end of growth.

Intra-Articular Cytokine Levels in Adolescent Patients after Anterior Cruciate Ligament Tear

The treatment of anterior cruciate ligament (ACL) injuries in children and adolescents is challenging. Preclinical and clinical studies investigated ACL repairing techniques in skeletally immature subjects. However, intra-articular bioenvironment following ACL tear has not yet been defined in skeletally immature patients. The aim of this study was to measure cytokine concentrations in the synovial fluid in adolescent population. Synovial levels of IL-1β, IL-1ra, IL-6, IL-8, IL-10, and TNF-α were measured in 17 adolescent patients (15 boys) with ACL tears who underwent ACL reconstruction including acute (5), subacute (7), and chronic (5) phases. Femoral growth plates were classified as “open” in three patients, “closing” in eight, and “closed” in six. Eleven patients presented an ACL tear associated with a meniscal tear. The mean Tegner and Lysholm scores (mean±SD) of all patients were 8 ± 1 and 50.76 ± 26, respectively. IL-8, TNF-α, and IL-1β levels were significantly greater in patients with “open” physes. IL-1ra and IL-1β levels were significantly higher in patients with ACL tear associated with a meniscal tear. Poor Lysholm scores were associated with elevated IL-6 and IL-10 levels. IL-10 levels positively correlated with IL-6 and IL-8 levels, whereas TNF-α concentration negatively correlated with IL-6 levels. Skeletally immature patients with meniscal tears and open growth plates have a characteristic cytokine profile with particularly elevated levels of proinflammatory cytokines including IL-8, TNF-α, and IL-1β. This picture suggests that the ACL tear could promote an intra-articular catabolic response in adolescent patients greater than that generally reported for adult subjects. The study lacks the comparison with synovial samples from healthy skeletally immature knees due to ethical reasons. Overall, these data contribute to a better knowledge of adolescent intra-articular bioenvironment following ACL injuries.