Simulation of orthotic treatment in adolescent idiopathic scoliosis using a subject-specific finite element model

Adolescent idiopathic scoliosis (AIS) is a threedimensional deformity of the spine, often progressing rapidly during the growth spurt. Severe scoliosis can lead to significant degradation of quality of life and functional impairment; the aim of early orthotic treatment is to slow down curvature progression until skeletal maturity. Efficacy of bracing has often been questioned (Negrini et al., 2010; Weinstein et al., 2013), and often relies on the orthotist’s experience since objective methods to design and predict brace action are still in development (Cobetto et al., 2014). A clinically-relevant method for the evaluation of brace simulation in AIS was recently presented (Vergari et al., 2015) and applied to preliminarily validate a finite element model (FEM) of the trunk. The aim of this work was to improve the simulation of brace action on scoliotic trunks and to validate the model on a larger cohor

Early detection of progressive adolescent idiopathic scoliosis : a severity index

Study Design. Early detection of progressive adolescent idiopathic scoliosis (AIS) was assessed based on 3D quantification of the deformity. Objective. Based on 3D quantitative description of scoliosis curves, the aim is to assess a specific deformation pattern that could be an early detectable severity index for progressive AIS. Summary of Background Data. Early detection of progressive scoliosis is important for adapted treatment to limit progression. However, progression risk assessment is mainly based on the follow up, waiting for signs of rapid progression that generally occur during the growth peak. Methods. 65 mild scoliosis (16 boys, 49 girls, Cobb Angle between 10 and 20°) with a Risser between 0 and 2 were followed from their first exam until a decision was made by the clinician, either considering the spine as stable at the end of growth (26 patients) or planning to brace because of progression (39 patients). Calibrated biplanar X-rays were performed and 3D reconstructions of the spine allowed to calculate six local parameters related to main curve deformity. For progressive curve 3D phenotype assessment, data were compared to those previously assessed for 30 severe scoliosis (Cobb Angle > 35°), 17 scoliosis before brace (Cobb Angle > 29°) and 53 spines of non-scoliosis subjects. A predictive discriminant analysis was performed to assess similarity of mild scoliosis curves either to those of scoliosis or non-scoliosis spines, yielding a severity index (S-index). S-index value at first exam was compared to clinical outcome. Results. At the first exam, 53 out of 65 predictions (82%) were in agreement with actual clinical outcome. 89 % of the curves that were predicted as progressive proved accurate Conclusion. Although still requiring large scale validation, results are promising for early detection of progressive curves

Towards a predictive simulation of brace action in adolescent idiopathic scoliosis

The data collection was approved of by the ethical commit-tee (CPP 6001 Ile de France V), and patients and their parents signed an informed consent.Bracing is the most common treatment to stop the progression of adolescent idiopathic scoliosis. Finite element modeling could help improve brace design, but model validation is still a challenge. In this work, the clinical relevance of a predictive and subject-specific model for bracing was evaluated in forty-six AIS patients. The model reproduces brace action and the patient’s spinopelvic adjustments to keep balance. The model simulated 70% or more patients with geometrical parameters within a preselected tolerance level. Although the model simulation of the sagittal plane could be improved, the approach is promising for a realistic and predictive simulation of brace action.The authors are grateful to the ParisTech BiomecAM chair program on subject-specific musculoskeletal modelling (with the support of ParisTech and Yves Cotrel Foundations, Proteor, Société Génerale and Covea). We are also thankful to David Barrie Colridge for his support

Quasi-automatic early detection of progressive idiopathic scoliosis from biplanar radiography: a preliminary validation

Purpose To validate the predictive power and reliability of a novel quasi-automatic method to calculate the severity index of adolescent idiopathic scoliosis (AIS). Methods Fifty-five AIS patients were prospectively included (Age: 10-15, Cobb: 16° ± 4°). Patients underwent low-dose biplanar x-rays and a novel fast method for 3D reconstruction of the spine was performed. They were followed until skeletal maturity (stable patients) or brace prescription (progressive patients). The severity index was calculated at the first exam, based on 3D parameters of the scoliotic curve, and it was compared with the patient’s final outcome (progressive or stable). Three operators have repeated the 3D reconstruction twice for a subset of 30 patients to assess reproducibility (through Cohen’s kappa and intraclass correlation coefficient). Results 85% of the patients were correctly classified as stable or progressive by the severity index, with a sensitivity of 92% and specificity of 74%. Substantial intra-operator agreement and good inter-operator agreement were observed, with 80% of the progressive patients correctly detected at the first exam. The novel severity index assessment took less than 4 minutes of operator time. Conclusions The fast and semi-automatic method for 3D reconstruction developed in this work allowed for a fast and reliable calculation of the severity index. The method is fast and user friendly. Once extensively validated, this severity index could allow very early initiation of conservative treatment for progressive patients, thus increasing treatment efficacy and therefore reducing the need for corrective surgery.BiomecA

Bioactive lipids as biomarkers of adverse reactions associated with apheresis platelet concentrate transfusion

Platelet concentrate (PC) transfusion seeks to provide haemostasis in patients presenting severe central thrombocytopenia or severe bleeding. PCs may induce adverse reactions (AR) that can occasionally be severe (SAR). PCs contain active biomolecules such as cytokines and lipid mediators. The processing and storage of PCs creates so-called structural and biochemical storage lesions that accumulate when blood products reach their shelf life. We sought to investigate lipid mediators as bioactive molecules of interest during storage and review associations with adverse reactions post-transfusion. To facilitate understanding, we focused on single donor apheresis (SDA) PCs with approximately 31.8% of PCs being delivered in our setting. Indeed, pooled PCs are the most widely transfused products, but the study of a single donor lipid mediator is easier to interpret. We are investigating key lipid mediators involved in AR. Adverse reactions were closely monitored in accordance with current national and regional haemovigilance protocols. Residual PCs were analysed post-transfusion in a series of observations, both with and without severe reactions in recipients. A decrease in the lysophosphatidylcholine species to produce the lysophosphatidic acid species has been observed during storage and in the case of AR. Lysophosphatidic acid increased with primarily platelet-inhibitor lipids. Anti-inflammatory platelet-induced inhibition lipids were weakly expressed in cases of severe adverse reactions. We therefore propose that a decrease in lysophosphatidylcholine and an increase in lysophosphatidic acid can prospectively predict serious adverse transfusion reactions

Influence of school bag carrying on gait kinetics.

International audienceThe purpose of this study was to determine the effect of different methods of backpack carrying on gait kinetics in children, using a new treadmill that allowed three-dimensional measurement of right and left leg ground reaction forces (GRFs). Forty-one healthy children, with a mean age of 12 years, participated in this study. The mean height was 152 cm and the mean weight 40 kg. The three trials consisted of walking on the treadmill at the speed of 3.5 km/h, first without a backpack and then carrying a 10 kg school bag on the right shoulder or on both shoulders. For each carrying condition GRFs were recorded, averaged, and analyzed for 30 steps. Stride, stance, double stance, thirteen specific GRF parameters and the symmetry index were measured. The right leg produced higher propulsive fore-aft forces than the left one, whatever the walking conditions. For the two maximum peaks and the average vertical force during stance, a statistical difference was found between walking without a backpack and carrying a backpack on one or two shoulders (one or two shoulder carrying > no backpack) but never between one-shoulder and two-shoulder carrying. The children increased their stance and double stance when walking with a backpack compared with walking without a pack. The symmetry index increased with one-strap carrying (compared with no backpack and two-strap carrying) for the maximum force during the breaking phase (Fy1) when it decreased for the maximum propulsive horizontal force before taking-off (Fy2). Children should be advised to carry their backpack on two shoulders rather than use a one-strap backpack

Head to Pelvis Alignment of Adolescent Idiopathic Scoliosis Patients Both in and Out of Brace

International audiencePurpose: To determine the short-term effect of bracing of adolescent idiopathic scoliotic (AIS) patients on the relationships between spinopelvic parameters related to balance, by comparing their in and out-of-brace geometry and versus healthy subjects. Methods: Forty-two AIS patients (Cobb angle 29° ± 12°, ranging from 16° to 61°) with a prescription of orthotic treatment were included retrospectively and prospectively. They all underwent biplanar radiography and 3D reconstruction of the spine and pelvis before bracing as well as less than 9 months after bracing. Eighty-three age-matched healthy adolescents were also included as control group and underwent biplanar radiography and 3D reconstruction. Results: Sacral slope was higher in AIS than healthy patients (p = 0.005). Bracing induced large changes of pelvic tilt (between - 9° and 9°), although patients' sagittal spinopelvic alignment tended to remain within the normality corridors defined by the healthy patients. Patients had flatter backs compared to healthy subjects and bracing further reduced their spinal curves. The head tended to remain above the pelvis in-brace. Conclusion: Analysis of sagittal alignment from head to pelvis showed that bracing further flattened the patients' backs and induced large compensating reorientations of the pelvis. Sagittal balance should be included in the planning and evaluation of brace treatment, since it could play a role in its outcome. These slides can be retrieved under Electronic Supplementary Material

Quasi-automatic early detection of progressive idiopathic scoliosis from biplanar radiography: a preliminary validation

International audiencePurpose To validate the predictive power and reliability of a novel quasi-automatic method to calculate the severity index of adolescent idiopathic scoliosis (AIS).Methods Fifty-five AIS patients were prospectively included (Age: 10-15, Cobb: 16° ± 4°). Patients underwent low-dose biplanar x-rays and a novel fast method for 3D reconstruction of the spine was performed. They were followed until skeletal maturity (stable patients) or brace prescription (progressive patients). The severity index was calculated at the first exam, based on 3D parameters of the scoliotic curve, and it was compared with the patient’s final outcome (progressive or stable). Three operators have repeated the 3D reconstruction twice for a subset of 30 patients to assess reproducibility (through Cohen’s kappa and intraclass correlation coefficient).Results 85% of the patients were correctly classified as stable or progressive by the severity index, with a sensitivity of 92% and specificity of 74%. Substantial intra-operator agreement and good inter-operator agreement were observed, with 80% of the progressive patients correctly detected at the first exam. The novel severity index assessment took less than 4 minutes of operator time.Conclusions The fast and semi-automatic method for 3D reconstruction developed in this work allowed for a fast and reliable calculation of the severity index. The method is fast and user friendly. Once extensively validated, this severity index could allow very early initiation of conservative treatment for progressive patients, thus increasing treatment efficacy and therefore reducing the need for corrective surgery

Effect of curve location on the severity index for adolescent idiopathic scoliosis: a longitudinal cohort study

Objectives Adolescent idiopathic scoliosis (AIS) is the most common spinal disorder in children. A severity index was recently proposed to identify the stable from the progressive scoliosis at the first standardized biplanar radiographic exam. The aim of this work was to extend the validation of the severity index and to determine if curve location influences its predictive capabilities. Methods AIS patients with Cobb angle between 10° and 25°, Risser 0–2, and no previous treatment were included. They underwent standing biplanar radiography and 3D reconstruction of the spine and pelvis, which allowed to calculate their severity index. Patients were grouped by curve location (thoracic, thoracolumbar, lumbar). Patients were followed up until skeletal maturity (Risser ≥ 3) or brace prescription. Their outcome was compared to the prediction made by the severity index. Results In total, 205 AIS patients were included; 82% of them (155/189, 95% confidence interval [74–90%]) were correctly classified by the index, while 16 patients were unclassified. Positive predictive ratio was 78% and negative predictive ratio was 86%. Specificity (78%) was not significantly affected by curve location, while patients with thoracic and lumbar curves showed higher sensitivity (≥ 89%) than those with thoracolumbar curves (74%). Conclusions In this multicentric cohort of 205 patients, the severity index was used to predict the risk of progression from mild to moderate scoliosis, with similar results of typical major curve types. This index represents a novel tool to aid the clinician and the patient in the modulation of the follow-up and, for progressive patients, their decision for brace treatment