BACKGROUND:Adolescent idiopathic scoliosis is a common spinal deformity that seriously affects the physical and mental health of patients.Modal analysis will focus on analyzing the natural vibration characteristics of the thoracic spine and its stability and response under the influence of external vibration.This analysis is expected to not only enhance the understanding of the thoracic curvature of adolescent idiopathic scoliosis,but also provide new perspectives and methods for developing new treatment strategies,designing personalized braces,and evaluating surgical outcomes.OBJECTIVE:To create a three-dimensional finite element model to evaluate the response modes of the entire thoracic spine and intervertebral discs in adolescent idiopathic scoliosis patients at different vibration frequencies,and determine the potential frequency range of injury risk.METHODS:This study was jointly conducted at the Sixth Affiliated Hospital of Xinjiang Medical University and the School of Mechanical Engineering at the Boda Campus of Xinjiang University from June 2023 to June 2024.The research subject was a patient with severe spinal and thoracic curvature.CT images were obtained using Siemens dual source spiral CT scanning,and a fine T1-T12 three-dimensional finite element model was established using software such as Mimics,Geomagic Studio,Solidworks,and Hypermesh.Abaqus software was used to perform modal analysis on the model and obtain the maximum amplitude and corresponding vibration modes of the first 12 modes of the entire thoracic spine and intervertebral disc.RESULTS AND CONCLUSION:(1)The modal analysis results showed that the entire thoracic vertebrae and intervertebral discs mainly bent and twisted around the X and Y axes in the lower order modes,while increasing rotation around the Z axis in the higher order modes.(2)The T1-T3 and T6-T8 segments showed the most significant deformation and higher load burden,indicating that these regions played a crucial role in the development of scoliosis.(3)When the natural frequency was concentrated between 98.832 to 121.97 cycles/s for a long time,the vibration displacement of the entire thoracic vertebrae and intervertebral discs was large,which might lead to spinal injury.(4)Through finite element modal analysis,this study provides a scientific basis for understanding the response of the entire thoracic spine and intervertebral discs in adolescent idiopathic scoliosis patients under various vibration frequencies,thereby offering crucial insights into clinical treatment,prevention,and particularly,vibration-related protective strategies.Furthermore,by identifying the potential frequency range of injury risk,this study provides an important basis for developing vibration protection measures and optimizing spinal care strategies for adolescent idiopathic scoliosis patients.

Objective To investigate the protective effect of cerebrospinal fluid(CSF)on the spinal cord in patients with scoliosis and evaluate its buffering effect during gravitational traction surgery and in daily life,so as to provide a theoretical guidance for surgical planning and postoperative rehabilitation of scoliosis.Methods A three-dimensional coupled spinal cord-CSF finite element model was established to simulate the biomechanical responses of the spine under two scenarios:gravitational traction surgery and daily life.Comparative analyses were conducted for conditions with and without CSF,and the buffering effect of CSF was quantitatively assessed.Results During simulated gravitational traction surgery,CSF significantly reduced the stress and deformation of the spinal cord,with the stress in spinal cord white and gray matter decreasing by 65％-90％and deformation decreasing by 70％-95％.In the daily life scenario,CSF provided greater protective effects in lateral flexion and anterior-posterior flexion directions,with stress reductions of 60％-85％.However,in torsion,the buffering effect of CSF was relatively weaker,with stress reductions of only 10％-25％.Conclusions CSF significantly reduces spinal cord stress and deformation during gravitational traction surgery and in daily life,reducing the risk of injury.

Objective To investigate the protective effect of cerebrospinal fluid(CSF)on the spinal cord in patients with scoliosis and evaluate its buffering effect during gravitational traction surgery and in daily life,so as to provide a theoretical guidance for surgical planning and postoperative rehabilitation of scoliosis.Methods A three-dimensional coupled spinal cord-CSF finite element model was established to simulate the biomechanical responses of the spine under two scenarios:gravitational traction surgery and daily life.Comparative analyses were conducted for conditions with and without CSF,and the buffering effect of CSF was quantitatively assessed.Results During simulated gravitational traction surgery,CSF significantly reduced the stress and deformation of the spinal cord,with the stress in spinal cord white and gray matter decreasing by 65％-90％and deformation decreasing by 70％-95％.In the daily life scenario,CSF provided greater protective effects in lateral flexion and anterior-posterior flexion directions,with stress reductions of 60％-85％.However,in torsion,the buffering effect of CSF was relatively weaker,with stress reductions of only 10％-25％.Conclusions CSF significantly reduces spinal cord stress and deformation during gravitational traction surgery and in daily life,reducing the risk of injury.

BACKGROUND:Adolescent idiopathic scoliosis is a common spinal deformity that seriously affects the physical and mental health of patients.Modal analysis will focus on analyzing the natural vibration characteristics of the thoracic spine and its stability and response under the influence of external vibration.This analysis is expected to not only enhance the understanding of the thoracic curvature of adolescent idiopathic scoliosis,but also provide new perspectives and methods for developing new treatment strategies,designing personalized braces,and evaluating surgical outcomes.OBJECTIVE:To create a three-dimensional finite element model to evaluate the response modes of the entire thoracic spine and intervertebral discs in adolescent idiopathic scoliosis patients at different vibration frequencies,and determine the potential frequency range of injury risk.METHODS:This study was jointly conducted at the Sixth Affiliated Hospital of Xinjiang Medical University and the School of Mechanical Engineering at the Boda Campus of Xinjiang University from June 2023 to June 2024.The research subject was a patient with severe spinal and thoracic curvature.CT images were obtained using Siemens dual source spiral CT scanning,and a fine T1-T12 three-dimensional finite element model was established using software such as Mimics,Geomagic Studio,Solidworks,and Hypermesh.Abaqus software was used to perform modal analysis on the model and obtain the maximum amplitude and corresponding vibration modes of the first 12 modes of the entire thoracic spine and intervertebral disc.RESULTS AND CONCLUSION:(1)The modal analysis results showed that the entire thoracic vertebrae and intervertebral discs mainly bent and twisted around the X and Y axes in the lower order modes,while increasing rotation around the Z axis in the higher order modes.(2)The T1-T3 and T6-T8 segments showed the most significant deformation and higher load burden,indicating that these regions played a crucial role in the development of scoliosis.(3)When the natural frequency was concentrated between 98.832 to 121.97 cycles/s for a long time,the vibration displacement of the entire thoracic vertebrae and intervertebral discs was large,which might lead to spinal injury.(4)Through finite element modal analysis,this study provides a scientific basis for understanding the response of the entire thoracic spine and intervertebral discs in adolescent idiopathic scoliosis patients under various vibration frequencies,thereby offering crucial insights into clinical treatment,prevention,and particularly,vibration-related protective strategies.Furthermore,by identifying the potential frequency range of injury risk,this study provides an important basis for developing vibration protection measures and optimizing spinal care strategies for adolescent idiopathic scoliosis patients.

Objective To study the biomechanical differences between hollow compression screws and shape-memory alloy staples in triple arthrodesis internal fixation and to provide references for the clinical application of shape-memory alloy staples.Methods Two-dimensional(2D)computed tomography(CT)foot data from a patient with severe horseshoe foot stiffness were selected,and a triple arthrodesis model was established using Mimics and Geomagic software.A geometric triple arthrodesis internal fixation model was established using SolidWorks 2021 software.Four fixation schemes(A,B,C,and D)were established according to the type and combination of fixed screws(hollow compression screws and shape-memory alloy riding nails).The biomechanical characteristics of models with different internal fixation schemes under neutral physiological loading were simulated and analyzed using ABAQUS software.Results The maximum end-face displacements of the fused surfaces of the talocalcaneal talonavicular and calcaneocuboid joints in the internal fixation model of scheme D were greater than those in schemes A,B,and C.The differences between the medial and lateral displacements of the fused surfaces of the talonavicular and calcaneocuboid joints in the internal fixation model of scheme D were 13.10％and 13.60％,respectively.The fused surface displacements were closer to the parallel displacements than those in the other three fixation schemes.The von Mises stresses were greater than those of schemes A,B,and C.Conclusions The application of scheme D(internal fixation at fusion surfaces of the talonavicular and calcaneocuboid joints with staples and at fusion surfaces of the talocalcaneal joints with compression hollow screws)provides stability at fusion surfaces of the internal fixation after triple arthrodesis surgery with near-parallel micromovement,which produces appropriate fusion stresses to make contact at the fusion end closer,promote the growth of bone scabs,and achieve better fusion results.

BACKGROUND:Halo gravity traction is a pre-operative traction method recognized by many scholars,but most of them rely on clinical observation and lack finite element analysis. OBJECTIVE:To explore the best traction force of Halo gravity traction on Lenke 3 scoliosis by finite element method and to provide a theoretical basis for clinics from a biomechanical point of view. METHODS:The CT images scanned by patients with scoliosis were processed by reverse modeling,and a finite element model was established.The validity of the model was verified by taking normal segments(T1-T4 vertebral bodies).Five groups of different stress conditions were set on the lumbar-thoracic scoliosis model to simulate the correction of patients under different traction forces.In all five groups,the lower surface of L5 was completely restrained,and different traction forces were applied to the upper surface of T1 along the positive direction of the Z axis(the opposite direction of gravity),which were 50,100,150,200,and 250 N,respectively.The displacement of the scoliosis spine,Cobb angle change of the main bending,elongation of the spine,and Von Mises stress were compared under different traction forces. RESULTS AND CONCLUSION:(1)When the Halo gravity traction force was 150 N to 200 N,the reduction of the Cobb angle of the main bending was 69.4%to 88.9%of the maximum reduction;the elongation of the Z axis was 69.4%to 85.9%,and the stress was 63.6%to 82.9%of the maximum stress.(2)When the traction force was greater than 200 N,the reduction of the Cobb angle and the elongation of the Z axis did not change obviously,but the stress value increased sharply.At this time,the distance from the centroids of T6,T7,and T8 to the vertical line of L5 was the most obvious.(3)When the Halo gravity traction force was 150 N to 200 N,the correction effect on this type of patient was the best—the reduction of Cobb angle and the elongation of the Z axis were better without the sharp increase in stress.(4)It has certain theoretical support for clinical correction and can ensure the safety of patients when scoliosis is corrected to a large extent.

Objective To evaluate the optimal traction amount for treating scoliosis using halo pelvic ring traction(HPRT)and provide theoretical references for clinical surgical assessment and rehabilitation.Methods A three-dimensional(3D)model of the thoracolumbar spine including the spinal cord was created and validated.Five traction amounts(10,15,20,25,30 mm)were applied to the model.The biomechanical responses of the spine under different traction conditions were simulated to determine the optimal amount of traction.Results As the traction increased,the Cobb angle decreased progressively.Significantly,in the range of 15-20 mm,the reduction in Cobb angle accounted for 50%-70.5%of the maximum reduction.The spinal stress at the main curvature represented 47.4%-67.5%of the maximum stress.Meanwhile,the stresses in the gray and white matter of the spinal cord were 70.3%-84.5%and 68.8%-83.9%of their respective maximum stresses.Conclusions The traction amounts between 15 mm and 20 mm are optimal for treating scoliosis.This range maximizes the Cobb angle correction while maintaining lower stress levels and thereby,reduces the risk of damage to the spine and spinal cord.

Objective To evaluate the optimal traction amount for treating scoliosis using halo pelvic ring traction(HPRT)and provide theoretical references for clinical surgical assessment and rehabilitation.Methods A three-dimensional(3D)model of the thoracolumbar spine including the spinal cord was created and validated.Five traction amounts(10,15,20,25,30 mm)were applied to the model.The biomechanical responses of the spine under different traction conditions were simulated to determine the optimal amount of traction.Results As the traction increased,the Cobb angle decreased progressively.Significantly,in the range of 15-20 mm,the reduction in Cobb angle accounted for 50%-70.5%of the maximum reduction.The spinal stress at the main curvature represented 47.4%-67.5%of the maximum stress.Meanwhile,the stresses in the gray and white matter of the spinal cord were 70.3%-84.5%and 68.8%-83.9%of their respective maximum stresses.Conclusions The traction amounts between 15 mm and 20 mm are optimal for treating scoliosis.This range maximizes the Cobb angle correction while maintaining lower stress levels and thereby,reduces the risk of damage to the spine and spinal cord.

To investigate the effects of postoperative fusion implantation on the mesoscopic biomechanical properties of vertebrae and bone tissue osteogenesis in idiopathic scoliosis, a macroscopic finite element model of the postoperative fusion device was developed, and a mesoscopic model of the bone unit was developed using the Saint Venant sub-model approach. To simulate human physiological conditions, the differences in biomechanical properties between macroscopic cortical bone and mesoscopic bone units under the same boundary conditions were studied, and the effects of fusion implantation on bone tissue growth at the mesoscopic scale were analyzed. The results showed that the stresses in the mesoscopic structure of the lumbar spine increased compared to the macroscopic structure, and the mesoscopic stress in this case is 2.606 to 5.958 times of the macroscopic stress; the stresses in the upper bone unit of the fusion device were greater than those in the lower part; the average stresses in the upper vertebral body end surfaces were ranked in the order of right, left, posterior and anterior; the stresses in the lower vertebral body were ranked in the order of left, posterior, right and anterior; and rotation was the condition with the greatest stress value in the bone unit. It is hypothesized that bone tissue osteogenesis is better on the upper face of the fusion than on the lower face, and that bone tissue growth rate on the upper face is in the order of right, left, posterior, and anterior; while on the lower face, it is in the order of left, posterior, right, and anterior; and that patients' constant rotational movements after surgery is conducive to bone growth. The results of the study may provide a theoretical basis for the design of surgical protocols and optimization of fusion devices for idiopathic scoliosis.
Humans ; Scoliosis/surgery* ; Spinal Fusion/methods* ; Lumbar Vertebrae/surgery* ; Osteogenesis ; Biomechanical Phenomena/physiology* ; Finite Element Analysis

Objective To investigate dynamic response of the finite element model of Lenke3 type scoliosis. Methods The finite element model was established based on CT scanning images from a patient with Lenke3 type scoliosis, and validation of the model was also conducted. Modal analysis, harmonic response analysis and transient dynamic analysis were carried out on the model. Results The first order natural frequency of this model was only 1-2 Hz.The amplitude of the finite element model was the largest at the first natural frequency. At the same resonance frequency, the amplitude of the thoracic curved vertebra was larger than that of the lumbar curved vertebra.The amplitude from T6 vertebra to L2 vertebra decreased successively. Conclusions The degree of spinal deformity may affect the perception of spine vibration, and the higher the degree of spinal deformity, the higher the sensitivity to vibration. The first natural frequency is most harmful to Lenke3 type scoliosis patients. Under cyclic loading, the thoracic curved vertebra is more prone to deformation than the lumbar curved vertebra. The closer to T1 segment, the greater the amplitude of the vibration is.