Papers by Keyword: Cervical Spine

Abstract: The cervical spine is a complex anatomical structure that mainly stabilizes the head and protects the spinal cord. Injuries of the cervical spine often occur during falls or road accidents and are particularly serious since they generate strong threats of paralysis and death. It should be noted that the ligaments provide cervical stability but their stabilization in case of injury is not yet well investigated. In this context, the objective of the present work is to study the failure of the ligaments by developing a bio-faithful numerical model while using a more realistic geometry of the spinal components and behavior laws that take into account the effect of strain rate and motion amplitudes. In order to validate the results of the study, we conducted a comparison with previous literature studies. It has been found that damage is often supported by intervertebral discs, anterior longitudinal ligaments (ALL) and capsular ligaments (CL) in the case of frontal impact. Indeed, the highest stresses are concentrated in the annulus fibrosus and the capsular ligaments. In this study, we tested the effect of ligament tears on disc behavior, where it was found that the stress rate increased by approximately 6%. The effect of capsular ligament tear orientation was also examined. The obtained results show that the most dangerous inclination was downward at an angle of 45°.

Abstract: The paper presents the studies realized a similar biomechanical system composed by neck, head and muscles complementary to the human neck. The model was defined starting with a real human object and which was made CT, after in a CAD environment, The main movements (axial rotation, lateral bending, and flexion-extension) has been obtained behavior based on date, tables or diagrams. The virtual model composed of the neck, head andmuscles, which was included in a complex system (similar with a car system), and a lot of virtual simulations car crash tests were made. As well is studied the behavior of shape memory springs, with which has been achieved anatomical-functional similarity with those of a human subject, comparing them in the end with the ones determined virtually with anatomical-myographic studies.

Abstract: Purpose To analyze the biomechanics of cervical spine after one-and two-level Total Disc Replacement (TDR) and two-level Anterior Cervical Discectomy and Fusion (ACDF). Methods Seven adult human cadaveric cervical spines were biomechanically evaluated under eccentric displacement control in six mechanical modes, including flexion (Flex), extension (Ext), left bending (LB), right rending (RB), left rotation (LR) and right rotation (RR). Results In fusion-treated specimens, range of motion (ROM) at instrumented level decreased as much as 81.78%, and other levels also demonstrated big difference in ROM. In arthroplasty-treated specimens, ROM showed little difference from that of the intact state. Large motion variation happened in LB, RB and Ext after both fusion and nonfusion surgical treatments. Conclusions TDR had a more reasonable motion sharing than ACDF, especially in Flex, Ext, LR and RR. No evident influence of motion change was observed after adding an extra level of TDR.

Abstract: The finite element method is often used in the field of biomechanical analysis. It can study the mechanical response of the internal organization without any experiments on the human body. The paper studies the biomechanics of the cervical spine by the method of finite element analysis. Firstly, the finite element model of the cervical spine including cervical vertebrae and soft tissue is constructed. Secondly, biomechanical analysis of cervical finite element model which is validated to be reasonable and reliable is completed. The results of the control group, the anterior cervical decompression and fusion surgery group, and the artificial cervical disc replacement surgery group are obtained to study the motion degree and ligament force of cervical spine. Thirdly, the summary of the biomechanical analysis of cervical finite element model is concluded.

Abstract: In order to obtain high-quality analytical results of the finite element model, it is essential to construct a three dimensional geometric model. The paper reconstructed an accurate three dimensional geometric model of cervical spine segments (C4-C7). The process of reconstruction included three-dimensional reconstruction, smooth processing, contour generation, grid generation and fitting surface. Moreover, the result of reconstruction was evaluated ultimately. The model was validated to be smooth and reasonable, and could meet the requirements of finite element analysis. The method is not merely applied to reconstruct the geometric model of the cervical spine. It is a way to construct the model of the skeletal system of the human body.

Abstract: Neck finite element models have been extensively applied to design and validate the artificial biomaterials. To date, many finite element models of European-American neck have been proposed. However, the issue that using the geometrical scaling to convert a western model into a Chinese neck model is highly controversial. A Chinese neck model, based on MRI/CT scan images and frozen slice images from a 35-year old male cadaver, was established in this paper to examine the geometrical difference between Chinese and European-American cervical vertebrae. Results showed that at every level of all cervical vertebrae except C2, a significant difference between the geometrical model of the Chinese and European-American cervical vertebrae was revealed. The authors suggested that there might be a significant difference between the Chinese and European-American cervical vertebrae.

Abstract: The cervical facet joint capsule is the major origin of neck pain. To in vivo test the cervical facet capsule strain, a flexible, miniature strain gauge was developed. A special liquid metal served as the strain sensitive element, and a tubular structure was selected as the configuration of this miniature strain gauge. Calibration tests and rear-end crash simulation experiments were performed to analyses the behavior of this new gauge. A physical head-neck model or living goat model was used as a human surrogate. Experiment results indicated the good linearity and stability of this miniature strain gauge. With the improvement of structural designs and manufacturing techniques, the miniature strain gauge stated in this paper has the potential to in vivo test the cervical facet capsule strain.

Abstract: The human spinal column is a highly complex and sophisticated system both from an engineering and neurological point of view, and provides a source of biomimetic inspiration for analysis of its function in trauma scenarios. A three-dimensional multi-body model of the 50th percentile male human and discretized neck were built for the study on cervical spine injuries in vehicle frontal impact. The discretized neck includes of cervical spine vertebrae, intervertebral discs, ligaments, and muscles. Following motor front crash evaluations, a finite element vehicle model was propelled straight ahead into a concrete barrier at a speed of 50 km/h. The longitudinal velocity of driver seat was decreased due to the absorbing energy function of the crumple zones. A Hybrid III adult male dummy was seated on a sled, restrained using safety belt, and longitudinal velocity measured from frontal impact was applied to simulate cervical spine injuries. The disk bending loads, interspinous ligament loads and disk shear strain of the cervical spine were analyzed in this paper.

Abstract: The biomechanical changes brought on by spine fusion and the artificial disc designs to restore physiologic motion were studied by using a cervical spine computer model. Fusion increased the motion compensation at the adjacent segment during flexion and extension. The global rotational stiffness and segmental disc forces were also increased after fusion. Among the three prosthetic disc designs, the PDD-III (5-DOF spherical joint in plane parallel with the C5-C6 disc level) maintained the normal motion and minimized load build up of adjacent segment.

Abstract: In this study, we introduced a virtual model and experimental simulator applicable to kinematics and kinetics analyses of the human cervical spine. The geometry of cervical vertebrae was created from computer tomography images. The disc joints were modeled as load-based joints having non-linear viscoelastic properties defined by data from in vitro experiments. The facet joints were modeled to rotate freely and translate along facet planes. Ligaments were modeled as nonlinear spring-damper elements. Simulated testing of the virtual model was conducted and the global stiffness response passed all of the statistical comparison tests. The model provided realistic visualization of in vitro experimental protocol.