Biomechanical effects of intervertebral disc degeneration on the cervical spine:a finite element analysis / 中国组织工程研究

BACKGROUND: The biomechanics of cervical spine is complicated. It is an important way to select the appropriate biomechanical model and research method so as to explore the diagnosis and evaluation mechanism of cervical spine injury and prognosis judgement.OBJECTIVE: To discuss the alternation of cervical biomechanics after the degeneration of cervical disc and the influence of degeneration on cervical stability.METHODS: (1) A three-dimensional finite element model of cervical spine was established from the CT scan images of cervical spine of a healthy male volunteer, Solid-Works2015, HyperMesh and ANSYS11.0. We created a cervical three-dimensional finite element model. To simulate the degenerative disc by modified the mechanical characters and height of the disc model, we observed the biomechanics of the impact on the cervical spine (the range and the stress on intervertabral disc).RESULTS AND CONCLUSION: (1) The entire model with a total of 97705 nodes and 372896 elements. Ligament and joint capsule were also constructed. Face to face contact element was used in the facet joint, with complete structure and high accuracy of measurement of spatial structure. (2) The range of motion of cervical spine increased during degeneration compared with normal cervical segments (P < 0.05). (3) Intervertebral disc degeneration caused angle increase at disc and motion segment. Osteophyte formed on vertebral edge. Intervertebral disc degeneration caused cervical instability. Simultaneously, instability increased the disc degeneration.

The influences upon the passive tensile of the masticatory muscles and ligaments by twin-block appliance under various bite reconstruction / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To study the regularity of the passive tensile of the masticatory muscles and ligaments by Twin-Block appliance under various bite reconstruction, and to provide some biomechanical references for the clinical use and improvement of Twin-Block appliance.</p><p><b>METHODS</b>"Temporomandibular joint, mandible and Twin-Block appliance" model was set up by the three dimensional finite element method, and the related masticatory muscles and ligaments were added on it. Seven experimental groups were designed according to the clinical and research, the occlusal inclined plate's angles of Twin-Block appliance were 40 degrees, 45 degrees, 50 degrees, 55 degrees, 60 degrees, 65 degrees and 70 degrees. The passive tensile in the masticatory muscles and ligaments were analyzed by the computer.</p><p><b>RESULTS</b>Under various experimental groups, the passive tensile in the anterior deep masseter (AM), the posterior deep masseter (PM), the anterior temporalis (AT), the posterior temporalis (PT), the stylomandibular ligament and sphenomandibular ligament improved with the increased slant angles of occlusal guide. The maximum value of the passive tensile was 82.57 N, the minimum value was 0.07 N.</p><p><b>CONCLUSION</b>1) In various experimental groups, AT, AM, PM, PT, stylomandibular ligament and sphenomandibular ligament are subject to passive tension force in the process of Twin-Block appliance guiding the mandibular forward and play the important role on the remodeling of the mandible. 2)All groups of occlusal inclined plate's angle are in physiologically tolerable range and can be used in clinic.</p>

Biomechanical research on different pairs of lumbar laminectomy with finite element analysis / 生物医学工程学杂志

The finite element model of the intact lumbar spine (L1-L5) was set up to study the biomechanical changes of three different pairs of the lumbar laminectomy. The three-dimensional finite elements model of L1-L5 vertebrae structure was constructed by the combination of self-compiled software and Hyper Mesh. The finite element model was compared with the experimental data in vitro. The finite element model was modified of stenosis at L3-L4 and L4-L5 with the same boundary conditions and physical loads to study the motion and loading in the annulus changes at the surgical site as a result of surgical alteration. The study suggested that the removal of posterior lumbar spinal elements for the treatment of stenosis at L3-L4 and L4-L5 produced a graded increase in motion at the surgical site, with the greatest changes occurring in flexion-extension and axial rotation and that during lateral bending the amount of resection was only slightly affected. The data showed that for flexion-extension and axial rotation the increases in motion were correlated to the extent of posterior element removal. It is necessary to retain the greatest degree of posterior lumbar structures in thorough decompression, which can further reduce the postoperative intervertebral disc, facet degeneration.

Bone remodeling numerical simulation on the basis of bone adaptive theory / 生物医学工程学杂志

In this paper, combined with the finite element (FE) method and optimization theory, a strain energy criterion is used to simulate and predict the bone remodeling. The strain energy density is taken as the mechanical stimulus. The bone remodeling is described as the changes of material distribution, which can represent the process of bone remodeling. By remodeling simulation of a two-dimensional proximal femur, a three-dimensional proximal femur and bone fracture healing plastic process, we demonstrate that this criterion can produce a realistic apparent density distribution in the proximal femur, and this criterion can well illuminate the mechanism of bone fracture healing plastic process.

Theoretical analysis and numerical simulation of effect of steel plate positions on steel plate rigidity in internal fixation of bone surgery / 生物医学工程学杂志

In this study we calculate theoretically and use FEM to simulate the effect of plate position relative to bending direction on the overall bending stiffness of the composite system plate-bone. The results show that for different bending directions the effect of the modulus of elasticity of the plate is negligible. Changing the position of a plate will often alter the stress obviously. During the operation, the steel plate should be assigned onto the tension side of the bone.