3D correction of AIS in braces designed using CAD/CAM and FEM: a randomized controlled trial

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

Efficacy of Computer-Aided Design and Manufacturing Versus Computer-Aided Design and Finite Element Modeling Technologies in Brace Management of Idiopathic Scoliosis: A Narrative Review

“…Although no significant difference in Cobb angle correction was obtained in group 2 [30], in group 3, the CAD-FEM brace resulted in significantly better in-brace curve correction than that of the conventional brace [53] (Table 4). In a study of Cobetto et al [55],…”

“…The correlation between brace-manufacturing methods and scoliosis treatment outcomes is controversial. Some studies have reported approximately the same Cobb angle correction between conventional versus CAD-CAM [28,30,54] and between conventional versus CAD-FEM methods [46,51], whereas other studies have shown that the Cobb angle was better corrected by CAD-FEM methods than by CAD-CAM or conventional methods [53,55]. Despite the controversial results in comparing the efficiency of brace-manufacturing methods, to the best of our knowledge, no study has yet carefully reviewed the effect of these methods on scoliosis parameters, such as spinal curve in coronal, sagittal, and transverse planes, and the patient's comfort.…”

“…Studies considering the efficacy of brace-manufacturing methods on clinical outcomes of scoliosis can be divided into four groups: group 1 studies investigated the efficacy of CAD-CAM braces in the treatment of scoliosis curve F [56,57], group 2 compared conventional versus CAD-CAM braces [28,30,54], group 3 compared conventional with CAD-FEM braces [46,51,53], and group 4 compared CAD-FEM with CAD-CAM braces [55]. In this review, the brace-manufacturing efficiency is discussed within this four-group classification for crossover and randomized clinical trial (RCT) study designs.…”

“…The RCTs investigated immediate in-brace curve correction for CAD-CAM versus conventional (group 2) [30] (Table 3), CAD-FEM versus conventional (group 3) (Table 4) [53], and CAD-CAM versus CAD-FEM [55] braces (group 4) ( Table 5). Although no significant difference in Cobb angle correction was obtained in group 2 [30], in group 3, the CAD-FEM brace resulted in significantly better in-brace curve correction than that of the conventional brace [53] (Table 4).…”

“…In RCT studies, however, CAD-FEM was the most effective method in terms of Cobb angle correction [53,55]. The reason for better outcomes from the CAD-FEM method might be related to optimization of the pad locations, which was not performed in the conventional method.…”