ABSTRACT
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.
ABSTRACT
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.
Subject(s)
Humans , Scoliosis/surgery , Spinal Fusion/methods , Lumbar Vertebrae/surgery , Osteogenesis , Biomechanical Phenomena/physiology , Finite Element AnalysisABSTRACT
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.
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Objective To study the effect of sand therapy on the hemodynamics of flexural femoral artery, and further reveal the therapeutic mechanism of sand therapy from the perspective of hemodynamics. Methods The three-dimensional finite element model of the curved femoral artery was established based on CT images of human aorta, and the data of heart rate, peak blood flow velocity and inner diameter of femoral artery measured by the experiment were used as initial conditions and boundary conditions to carry out finite element numerical simulation. The blood flow velocity, pressure and wall shear stress before and after sand therapy were analyzed and compared under fluid-solid coupling condition. Results Compared with treatment before sand therapy, the longitudinal velocity of the flexural segment of blood vessel increased significantly, with an increase of 22.76%. The secondary reflux velocity decreased significantly, with a relative decrease of 18.26%. The wall shear stress decreased by 2.01% after sand therapy. Conclusions Sand therapy had a significant effect on blood fluidity, by improving blood flow of femoral arteries, and preventing deposition of arterial platelets. The transverse flow phenomenon was obviously weakened after sand therapy, which could avoid the deposition of substances in blood and had a positive effect on the prevention of atherosclerosis, thrombosis and other vascular diseases.
ABSTRACT
Objective To study the effect of sand therapy on the hemodynamics of flexural femoral artery, and further reveal the therapeutic mechanism of sand therapy from the perspective of hemodynamics. Methods The three-dimensional finite element model of the curved femoral artery was established based on CT images of human aorta, and the data of heart rate, peak blood flow velocity and inner diameter of femoral artery measured by the experiment were used as initial conditions and boundary conditions to carry out finite element numerical simulation. The blood flow velocity, pressure and wall shear stress before and after sand therapy were analyzed and compared under fluid-solid coupling condition. Results Compared with treatment before sand therapy, the longitudinal velocity of the flexural segment of blood vessel increased significantly, with an increase of 22.76%. The secondary reflux velocity decreased significantly, with a relative decrease of 18.26%. The wall shear stress decreased by 2.01% after sand therapy. Conclusions Sand therapy had a significant effect on blood fluidity, by improving blood flow of femoral arteries, and preventing deposition of arterial platelets. The transverse flow phenomenon was obviously weakened after sand therapy, which could avoid the deposition of substances in blood and had a positive effect on the prevention of atherosclerosis, thrombosis and other vascular diseases.