Abstract
BackgroundRecent studies showed that finite element model (FEM) combined to CAD/CAM improves the design of braces for the conservative treatment of adolescent idiopathic scoliosis (AIS), using 2D measurements from in-brace radiographs. We aim to assess the immediate effectiveness on curve correction in all three planes of braces designed using CAD/CAM and numerical simulation compared to braces designed with CAD/CAM only.MethodsSRS standardized criteria for bracing were followed to recruit 48 AIS patients who were randomized into two groups. For both groups, 3D reconstructions of the spine and patient’s torso, respectively built from bi-planar radiographs and surface topography, were obtained and braces were designed using the CAD/CAM approach. For the test group, 3D reconstructions of the spine and patient’s torso were additionally used to generate a personalized FEM to simulate and iteratively improve the brace design with the objective of curve correction maximization in three planes and brace material minimization.ResultsFor the control group (CtrlBraces), average Cobb angle prior to bracing was 29° (thoracic, T) and 25° (lumbar, L) with the planes of maximal curvature (PMC) respectively oriented at 63° and 57° on average with respect to the sagittal plane. Average apical axial rotation prior to bracing was 7° (T) and 9° (L). For the test group (FEMBraces), initial Cobb angles were 33° (T) and 28° (L) with the PMC at 68° (T) and 56° (L) and average apical axial rotation prior to bracing at 9° (T and L). On average, FEMBraces were 50% thinner and had 20% less covering surface than CtrlBraces while reducing T and L curves by 47 and 48%, respectively, compared to 25 and 26% for CtrlBraces. FEMBraces corrected apical axial rotation by 46% compared to 30% for CtrlBraces.ConclusionThe combination of numerical simulation and CAD/CAM approach allowed designing more efficient braces in all three planes, with the advantages of being lighter than standard CAD/CAM braces. Bracing in AIS may be improved in 3D by the use of this simulation platform. This study is ongoing to recruit more cases and to analyze the long-term effect of bracing.Trial registrationClinicalTrials.gov, NCT02285621
Highlights
Recent studies showed that finite element model (FEM) combined to CAD/Computer-aided design/computer-aided manufacturing (CAM) improves the design of braces for the conservative treatment of adolescent idiopathic scoliosis (AIS), using 2D measurements from in-brace radiographs
Average Cobb angle prior to bracing was 29° (T) and 25° (L) and the apical axial rotation was of 7° for the T curve and 9° for the L curve with respective planes of maximum curvature (PMC) oriented at 63° and 57° with respect to the sagittal plane
Average Cobb angle prior to bracing was 33° (T) and 28° (L) and the average apical axial rotation was of 9° for both T and L curves, with respective PMC of 68° and 56°
Summary
Recent studies showed that finite element model (FEM) combined to CAD/CAM improves the design of braces for the conservative treatment of adolescent idiopathic scoliosis (AIS), using 2D measurements from in-brace radiographs. Orthopedic bracing is the conservative treatment generally prescribed to control curve progression in adolescent idiopathic scoliosis (AIS) showing curves between 20° and 40° of Cobb angle [1]. AIS is a threedimensional (3D) deformity of the spine which includes a deviation in the coronal plane, changes in the sagittal curves, and an axial rotation of the vertebrae [2, 3]. Bracing was demonstrated as an effective treatment to prevent curve progression, as assessed using 2D coronal X-ray measurements, and immediate in-brace correction was found to be correlated to long-term effectiveness [4,5,6,7]. Studies reported that brace wear tends to create a hypokyphotic effect and provide a non-significant correction of vertebral axial rotation [13, 14], as well as having no effect on the orientation of the planes of maximum curvature (PMC), which are defined by the planes passing through the apex and the end vertebrae of a given curve [2, 13, 15]
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