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case_images: The musculoskeletal finite element model was constructed for Rigo A classification. (A) Radiographic data of the spine and pelvis were obtained by CT. (B) The skeleton of the model was optimized and the whole spine-pelvis musculoskeletal assembly model was established.
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case_images: Research Triangle Park, NC, USA) in STL format to process the uneven surface of the medical image accumulation (Figure 1A). Spring elements were used to simulate ligaments between the vertebrae (Figure 1B). Muscle forces and reaction moments were estimated in the upright-standing posture under load gravity simulation, which was constrained to equilibrium and stability conditions, and the scoliotic curvature and stress distribution were calculated (Figure 1B).
case_images: Red arrows represent the direction of gravity and muscle force application, (A) represents the mixing force, C-K (B) represents magnitude of the applied force.schematic diagram of loads at different vertebral levels under FEM simulated gravity and muscle factors (spine-plevis FEM) vertical and downward gravity load is applied to the surface of the vertebrae.
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case_images: The musculoskeletal FEM of the AIS-simulated forces in the upright-standing position of the patient is shown in Figure 2.
case_images: Schematic diagram of the meshs, where (A) is the vertebra, (B) is the disc, and (C) is the torso and pelvis.
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case_images: The meshs quality check criteria are as follows: aspect ratio <= 5 , maximum Angle >= 30 , minimum angle <= 120 , Jacob ratio > 0.7, warpage ratio <= 0.6.At this time, the meshs of vertebrae and the whole torso is shown in Figure 3A. The overall torso meshes model is shown in Figure 3C.
case_images: Comparison of the geometric shape of the patient's full spine anterior-lateral radiographs with the finite element model.
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case_images: To verify the geometric similarity of the model, the spinal imaging parameters of the model were measured after gravity loading (Figure 4).
case_images: Comparison of vertebral segment ROM with previous studies. (A) Comparison of ROM from T1 to T4. (B) Comparison of ROM from T1 to T4.
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case_images: T5-T8 in the model was verified. The T1-T4 segment ROM simulation results were verified (Figure 5A); the stimulated ROM values in this model were consistent with anterior flexion, dorsal extension, left/right flexion, and left/right rotation ROM values from previous research models. T5-T8 segment ROM (Figure 5B) revealed that the anterior flexion values and left/right rotation ROM simulated in the selected segments of this model were higher than those values obtained by Busscher et al. and Xin et al.. The location of the top of the main thoracic (MT) curvature, the different degrees and types of lateral curvatures, and the older age in the previous models may make the ROM values of this model slightly larger than those of previous models.
case_images: Correct force finite element model of Cheneau brace Simulate the correction mechanism according to the concept of the Cheneau brace. (A) Arrows indicate the direction of the applied correction force and the red areas represent the area of the corrected force applied. (B) The direction of applied stress force is as follows: alpha represents a thrust applied on left axillary lateral (alpha1 represents upward axillary extension inferior), beta represents a thrust applied on Right thorax lateral (beta1 represents-upward axillary extension inferior), gamma represents a thrust applied on Left lumbar posterior, and delta represents gravity and muscle force applied on trunk. The model's pelvis and sacral canals were restricted to X, Y, and Z axis of freedom, and T1 was allowed to do lateral bending, forward bending and upward extension.
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case_images: Previous studies have shown that the corrective thrust was applied to the right chest to correct the right thoracic curve, the corrective reaction force was applied to the left axilla and the left lumbar side, and an upward extension force was applied to the axillae (400 N on the left and 200 N on the right) to simulate the "bending effect" and the "antigravity effect" of the brace (Figure 6).
case_images: Schematic representation of the convex and concave lateral pressure points of the intervertebral disc. (A) Convex side and the concave side points of T1-T2 disc. (B) Anterior and posterior points of T1-T2 disc.
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case_images: T2 (for T1-T2, T2-T3, T6-T7, and T7-T8) were measured and calculated. Third, the von Mises stress ratios for the concavities and convexities of the T1-T2, T2-T3, T6-T7, and T7-T8 discs were determined. The average value for the IVD stress was obtained by taking 10 points in the convex and concave, respectively (Figure 7).