The application of finite element analysis to determine the optimal UIV of growing-rod treatment in early-onset scoliosis

Abstract

Objectives: To analyze the stress distribution in the proximal vertebral body and soft tissue of dual growing-rod (GR) with different upper instrumented vertebra (UIV) to determine the optimal UIV.Methods: A ten-year-old male EOS case treated with GR was selected. Based on spiral computed tomography (CT) scanning performed in 0.6 mm thick slices, a finite element model (FEM) of the preoperative state (M0, the original spine state) of the patient was created. Subsequently, four models with different UIV fixations were numerically analyzed by FEM, including M1 (UIV = T1, i.e., the upper-end vertebrae (UEV) of the upper thoracic curve), M2 (UIV = T2), M3 (UIV = T3) and M4 (UIV = T4, i.e., the lower end vertebrae (LEV) of the upper thoracic curve). Displacement and maximum stress in the proximal vertebral body and soft tissue were measured and compared among the five models.Results: The spine model was fixed with the sacrum, and the gravity conditions were imposed on each vertebral body according to the research of Clin and Pearsall. The results are as follows:M4 model has the largest overall displacement, while M1 has the least displacement among the four models. Except M2, the maximum normalized stress of UIV increases with the downward movement of UIV. M1 has the lowerest annulus fibrosus stress and highest joint capsule stress, which is characterized by the vertebrae backward leaning, while M4 is the opposite. The supraspinous ligament stress of M3 and M4 is significantly higher than that of M1 and M2. This suggests that UIV downshift increases the tendency of the proximal vertebral bodies to bend forward, thereby increasing the tension of the posterior ligaments (PL).Conclusion: The UIV of the GR is recommended to be close to the UEV of the upper thoracic curve, which can reduce the stress of the proximal PL, thereby reducing the occurrence of proximal junctional kyphosis (PJK).

Finite element study on three osteotomy methods for treating thoracolumbar osteoporotic fracture vertebral collapse complicated with neurological dysfunction

“…By simulating postoperative loading conditions under physiological conditions during walking, cyclic loading can be used to create a similar model for studying screw pullout in patients with osteoporosis. Pan and Buell et al [22,23] constructed a finite element model of spinal deformity internal In this study, 3 finite element models of osteoporotic kyphosis with neurological dysfunction were successfully created, and their validity was confirmed by comparing the range of motion of normal segments with that of normal models. The results showed that the internal fixation stress and internal displacement in the BDBO group were significantly higher than those in the other 2 groups, and the stress on the titanium mesh reached 1328 MPa under left flexion conditions.…”

“…By simulating postoperative loading conditions under physiological conditions during walking, cyclic loading can be used to create a similar model for studying screw pullout in patients with osteoporosis. Pan and Buell et al [ 22 , 23 ] constructed a finite element model of spinal deformity internal fixation to simulate vertebral load. Through local mechanical distribution, local displacement, and other conditions of fixed segments, they analyzed the occurrence of Proximal Junctional Kyphosis (PJK) after spinal deformity correction surgery from a mechanical perspective, and obtained reliable data.…”