We observed the effect of vibration parameters on lumbar spine under different vibration conditions using finite element analysis method in our laboratory. In this study, the CT-images of L1-L5 segments were obtained. All images were used to develop 3D geometrical model using the Mimics10. 01 (Materialise, Belgium). Then it was modified using Geomagic Studio12. 0 (Raindrop Geomagic Inc. USA). Finite element (FE) mesh model was generated by Hypermesh11. 0 (Altair Engineering, Inc. USA) and Abaqus. Abaqus was used to calculate the stress distribution of L1-L5 under different vibration conditions. It was found that in a vibration cycle, tensile stress was occurred on lumbar vertebra mainly. Stress distributed evenly and stress concentration occurred on the left rear side of the upper endplate. The stress had no obvious changes under different frequencies, but the stress was higher when amplitude was greater. In conclusion, frequency and amplitude parameters have little effect on the stress distribution in vertebra. The stress magnitude is positively correlated with the amplitude.
Biomechanical Phenomena ; Finite Element Analysis ; Humans ; Lumbar Vertebrae ; physiology ; Vibration

According to the physiological characteristics of lumbar vertebrae in Chinese, we designed and made a lumbar vertebral fusion cage of titanium and then engaged in its biomechanical test. T12-S1 of lumbar vertebrae from 18 fresh dead bodies were used. We measured the stress relaxation and the creep effects of the normal group (T12-S1 of intact lumbar vertebrae), the control group 1(simulating operation of excising intervertebral disc and planting bone on the back route) and the control group 2(simulating operation of excising intervertebral disc and inserting fusion cage). The data and stress, strain-time curves under the condition of constant stress and strain were obtained. Regression analysis yielded the reduced stress relaxation and creep functions. Finally, we analyzed and discussed the effects of the operation of excising intervertebral disc and planting bone on the back route and the operation of excising intervertebral disc and inserting fusion cage on the stability of spine.
Elasticity ; Humans ; Intervertebral Disc ; physiology ; surgery ; Lumbar Vertebrae ; physiology ; Spinal Fusion ; Spine ; Titanium

OBJECTIVETo explore the mechanical behavior of lumbar spine loaded by stress and provide the mechanical basis for clinical analysis and judgement of lumbar spine fracture classification, mechanical distribution and static stress.

METHODSBy means of computer simulation method, the constructed lumbar spine three-dimensional model was introduced into three-dimensional finite element analysis by software Ansys 7.0. The lumbar spine mechanical behavior in different parts of the stress loading were calculated. Impact load is 0-8000 N. The peak value was 8000 N. The loading time is 0-40 minutes. The values of the main stress, stress distribution and the lumbar spine unit displacement in the direction of main stress were analyzed.

RESULTSThe lumbar spine model was divided into a total of 121 239 nodes, 112 491 units. It could objectively reflect the true anatomy of lumbar spine and its biomechanical behavior and obtain the end-plate images under different stress. The stress distribution on the lumbar intervertebral disc (L(3)-L(4)) under the axial, lateral flexion and extension stress, and the displacement trace of the corresponding processus articularis were analyzed.

CONCLUSIONIt is helpful to analyze the stress distribution of lumbar spine and units displacement in static stress loading in the clinical research of lumbar spine injury and the distribution of internal stress.

Adult ; Biomechanical Phenomena ; Female ; Finite Element Analysis ; Humans ; Lumbar Vertebrae ; physiology ; Sacrum ; physiology ; Stress, Mechanical

OBJECTIVETo observe the tested results of the segmental range of motion (ROM) of lumbar spine by charge couple device (CCD)-based system for 3-dimensional real-time positioning (CCD system), and to analyze its clinical significance.

METHODSSeven patients with lumbar joint dysfunction and 8 healthy subjects were tested twice by the CCD-based system with an interval of 10 min.

RESULTSThe ROM of the patients was obviously lesser than that of the healthy subjects. The measuring data of segmental ROM of lumbar spine by CCD system is correlated significantly to the same data checked later on the same subjects in every direction of the movements. The differences between two checks are usually less than 1 degree.

CONCLUSIONSpecially designed CCD based system for 3-dimensional real-time positioning could objectively reflect the segmental ROM of lumbar spine. The system would be of great clinical significance in the assessment of the biomechanical dysfunction of lumbar spine and the effect of the treatment applied.

Computer Systems ; Humans ; Lumbar Vertebrae ; physiology ; Orthopedic Equipment ; Range of Motion, Articular ; physiology

OBJECTIVETo compare the influence of normal and degenerative discs on stress distribution of the thoracolumbar vertebrae under destructive load, explore the biomechanical background and clinical meaning and provide theoretical basis for clinical diagnosis and treatment.

METHODSA mechanical model of thoracolumbar motion segment of normal and degenerative discs was built with a three dimensional finite element method and three stresses of vertical compression, compressive flexion and distractive flexion were comparatively analyzed.

RESULTSWith vertical compression and compressive flexion loads, the thoracolumbar motion segment of the normal disc showed that the central part of the upper and lower end-plates of the vertebrae and the central part of the trabecular bone adjacent to the end-plate were loaded with the most intensive stresses, meanwhile, the postero-lateral part of the annulus fibrosus was concentrated with stresses. Degenerative disc showed that the stress distribution of the trabecular bone was relatively averaged, the stresses of the central part adjacent to the end-plate were low, while at the same time, the stresses of the peripheral part were elevated relatively. With distraction flexion load, the stresses of the cortex bone, trabecular bone, end-plate and annulus fibrosus of the thoracolumbar vertebrae of degenerative discs were low, meanwhile, the stresses of the posterior structure of the vertebral body were relatively elevated compared with that of normal discs.

CONCLUSIONSThere is difference in influence between normal and degenerative discs on the stress distribution of the thoracolumbar vertebrae with destructive load. The transferring way of load is changed after disc degeneration.

Elasticity ; Finite Element Analysis ; Humans ; Lumbar Vertebrae ; physiology ; Spinal Injuries ; physiopathology ; Stress, Mechanical ; Tensile Strength ; Thoracic Vertebrae ; physiology

We tested the mechanical properties of fiber layers in adult anulus fibrosus of lumbar interverbral disc 4,5. Aulus fibrosus of lumbar interverbral disc was delaminated by using microsurgical technique. 8 testing points were taken in each layer according to the fibers going and 5 testing specimens were taken from each testing point. The length was 15-20mm, the width 1-2mm, and the thickness 0. 1-0. 5mm. By using tension test,the relationship curves of stress and strain were tested, the fitting curves and equations were obtained, and then the elastic modulus, damage strain and damage stress were obtained. Therefore we knew the parameters and equations of mechanical properties of each testing point. We got the result that the elastic modulus of each testing point, along the radius from outside to inside, decreased with the increase of layers. The damage stress decreased linearly from outside to inside. The damage strains of the outside 9 layers increased slightly with the increase of layers, and the others were almost constants, i. e. 0.34 +/- 0.14. We get the conclusion that analus fibrosus of intervertebral disc has special mechanical properties corresponding with its functions, which is in a close relationship with lumbar vertebral diseases.
Adult ; Biomechanical Phenomena ; Elasticity ; Humans ; Intervertebral Disc ; physiology ; Lumbar Vertebrae ; physiology ; Male ; Stress, Mechanical ; Tensile Strength ; physiology

We have studied the characteristics of stress relaxation and creep on lumbar vertebrae(T12-T5) of 18 fresh corpses. We measured the stress relaxation and creep of the normal group(intact spine), the control group 1(simulating the operations by the front route) and the control group 2(simulating the operations by the back route). Then we obtained the stress, strain-time curves and data under the conditions of constant stress and strain. By using regression analysis we obtained the reduced stress relaxation and creep functions. Finally, We analyzed and discussed the effects of the operations of excising the disc intervertebrales by the front route and the back route.
Diskectomy ; methods ; Elasticity ; Humans ; Lumbar Vertebrae ; physiology ; surgery ; Male ; Relaxation ; Stress, Mechanical

In order to study the mechanical behavior of degeneration and nucleotomy of lumbar intervertebral disc, compression experiments with porcine lumbar intervertebral discs were carried out. The lumbar intervertebral discs with trypsin-treated and nucleus nucleotomy served as the experimental group and the normal discs as the control group. Considering the effects of load magnitude and loading rate, the relationship between stress and strain, instantaneous elastic modulus and creep property of intervertebral disc were obtained. The creep constitutive model was established. The results show that the strain and creep strain of the experimental group increase significantly with the increase of compression load and loading rate, whereas the instantaneous elastic modulus decreases obviously, compared with the control group. It indicates that the effect of load magnitude and loading rate on load-bearing capacity of intervertebral disc after nucleotomy is larger obviously than that of normal disc. The creep behavior of the experimental group can be still predicted by the Kelvin three-parameter solid model. The results will provide theoretical foundation for clinical treatment and postoperative rehabilitation of intervertebral disc disease.
Animals ; Biomechanical Phenomena ; Intervertebral Disc ; physiology ; surgery ; Lumbar Vertebrae ; Stress, Mechanical ; Swine ; Weight-Bearing

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

We observed the structure and form of adult annulus fibrosus of lumbar intervertebral disc at the fibrous layer level. The annulus fibrosus of lumbar interverbral disc was delaminated by using microsurgical technique. 8 testing points were taken in each layer and the angles between their fibers going and horizontal plane were measured. The results showed that the fiber going angle at each measurement point continually increased with the increase of fibrous layer from outside to inside along the radial direction in horizontal plane. The least fiber going angle was 25 degrees - 30 degrees. The fiber going angle at the same layer gradually increased from front to back. The fiber going angle was 70 degrees - 90 degrees at the middle of the back of annulus fibrosus of lumbar interverbral disc. The fiber going was consistent with the posterior longitudinal ligament going. Through the normalized equation and normalized line, the fiber going angle at any point in any layer could be obtained conveniently. We also observed that the annuli fibrosus were interlaced in the front, left and right of annulus fibrosus of lumbar intervertebral disc. And there were more interlaced areas in local sides of lumbar intervertebral disc, but there was no interlaced areas between layers near the middle of posterior annulus fibrosus. So we came to the conclusion: Annulus fibrosus of lumbar intervertebral disc has a special micro-structure in adaptation with its function.
Adult ; Compressive Strength ; Fibrillar Collagens ; physiology ; Humans ; Intervertebral Disc ; anatomy & histology ; physiology ; Lumbar Vertebrae ; anatomy & histology ; Male ; Middle Aged