Surgical Outcome Prediction Using a Four-Dimensional Planning Simulation System With Finite Element Analysis Incorporating Pre-bent Rods in Adolescent Idiopathic Scoliosis: Simulation for Spatiotemporal Anatomical Correction Technique

Abstract

An optimal surgical strategy for adolescent idiopathic scoliosis (AIS) is to provide maximal deformity correction while preserving spinal mobile segments as much as possible and obtaining a balanced posture. From a spatiotemporal deformity correction standpoint, we recently showed that anatomical four-dimensional (4D) spinal correction could be accomplished by curving the rod. In the surgical procedure, two rods are bent identically to confirm spinal anatomical alignment without referring to the intraoperative alignment of the deformity. Therefore, anatomically designed rods have been developed as notch-free, pre-bent rods for easier anatomical reconstruction. In addition to providing the best spinal instrumentation configurations as pre-bent rods, prediction of surgical outcome along with its biomechanical impact can be obtained by simulation of the surgical procedures with computer modeling. However, an objective model that can simulate the surgical outcome in patients with AIS has not been completely elucidated. The present study aimed to compare simulated deformity corrections based on our newly developed spatiotemporal morphological 4D planning simulation system incorporating pre-bent rods and actual deformity corrections in patients with AIS. A consecutive series of 47 patients who underwent anatomical posterior correction for AIS curves were prospectively evaluated. After multilevel facetectomy, except for the lowest instrumented segment, 11 types of pre-bent rods were used. Patient demographic data, radiographic measurements, and sagittal rod angles were analyzed within 1 week of surgery. Our simulation system incorporating pre-bent rods showed a significant correlation with the actual postoperative spinal alignment. The present study demonstrated the feasibility of our simulation system and the ability to simulate the surgical procedure using the pre-bent rods. The simulation system can be used to minimize the differences between the optimal and possible outcomes related to the instrumentation levels and rod shapes. Preoperative assumption of rod shape and length can contribute to a reduction in operative time which decreases blood loss and risk of infection. The results of the finite element analysis in the simulation system measured for each individual patient would also provide a more realistic representation of the surgical procedures.

Elucidation of the Mechanism of Occasional Anterior Longitudinal Ligament Rupture with Posterior Correction Procedure for Adult Spinal Deformity Using LLIF–Finite Element Analysis of the Impact of the Lordotic Angle of Intervertebral LLIF Cage

“…The raw data collected in the DICOM format were imported into Mimics Research 23.0 (Materialize, Leuven, Belgium) to generate 3D vertebral models in a standard triangle language (STL). Subsequently, the generated STL data were imported into the ANSYS Workbench 2020 in the form of a solid 3D structure, which was built of 10-node tetrahedral element meshes [ 30 ]. The model was imported in STL format to 3-matice 15.0, allowing us to inspect the surface model for crisscrosses, tiny channels, or other artifacts (e.g., noise) and repair the triangles in the mesh structure.…”

“…FEA is a method used mainly in industrial fields, such as the construction industry, to perform mechanical simulations using a computer. Based on the design drawings of buildings and automobiles, three-dimensional (3D) models are created on a computer and converted into polyhedral called finite elements, and the stress, deformation, and motion of each element with respect to load and motion are predicted and analyzed [ 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 ]. When correction surgery for ASD is planned, computed tomography (CT) is usually performed before surgery for diagnosis and treatment, and the surgical plan is also made using 3D measurements constructed from the CT data.…”

Finite element analysis for mechanism of occasional anterior longitudinal ligament rupture with posterior correction procedure for adult spinal deformity using LLIF

“…The raw data collected in the DICOM format were imported into Mimics Research 23.0 (Materialize, Leuven, Belgium) to generate 3D vertebral models in a standard triangle language (STL). Subsequently, the generated STL data were imported into the ANSYS Workbench 2020 in the form of a solid 3D structure, which was built of 10-node tetrahedral element meshes [25]. The model was imported in STL format to 3-matice 15.0, allowing us to inspect the surface model for crisscrosses, tiny channels, or other artifacts (e.g., noise) and repair the triangles in the mesh structure.…”

“…FEA is a method used mainly in industrial elds, such as the construction industry, to perform mechanical simulation using a computer. Based on the design drawings of buildings and automobiles, three-dimensional (3D) models are created on a computer and converted into polyhedral called nite elements, and the stress, deformation, and motion of each element with respect to load and motion are predicted and analyzed [17][18][19][20][21][22][23][24][25]. When we perform correction surgery for ASD, computed tomography (CT) is usually performed before surgery for diagnosis and treatment, and the surgical plan is also made using 3D measurements constructed from the CT data.…”

Four-Dimensional Anatomical Spinal Reconstruction in Thoracic Adolescent Idiopathic Scoliosis

“…With both rod types, the cranial apex is created. There are 11 shapes of pre-bent, notch-free, cobalt-chromium alloy rods available in Japan 7-9 . Once the 2 spinal rods are connected to all polyaxial screw heads, the rods are simultaneously rotated 1,2,5,7 .…”