ABSTRACT
Objective To establish the precise finite element model of the head and neck based on human anatomical structure, so as to study neck injuries caused by rear impact at different speeds. Methods The model was based on CT scan images of the head and neck of human body. The Mimics software was used to reconstruct the three-dimensional (3D) bone, and the 3D solid ligaments, small joints and other tissues of the neck were improved and meshed by HyperMesh. The generated models included the head, 8 vertebrae (C1-T1), 6 intervertebral discs (annulus, nucleus pulposus and upper and lower cartilage endplates), facet joints (cartilage and joint capsule ligaments), ligaments, muscles, etc. Finally, the model verification and post-collision calculation were completed in the finite element post-processing software. Results The simulation results of the models under axial impact, front and back flexion and lateral flexion were compared with the experimental data to verify the effectiveness of the model. Then post-collision simulation at the speed of 20, 40, 60 and 80 km/h was conducted. At the speed of 20 km/h, there was no damage to the neck. At the speed of 40, 60 and 80 km/h, the ligament was the first to be damaged. As the speed increased, the stress on tissues of the neck increased continuously. At the speed of 80 km/h, the maximum stresses of the dense bone, cancellous bone and annulus of the cervical vertebrae were 226.4, 11.5, and 162.8 MPa, respectively. When the ligament strain reached the limit, tearing began to occur. Conclusions The finite element model of the head and neck established in this study has high bionics and effectiveness, and can be used for studying neck injury analysis in traffic accidents, which is helpful for the diagnosis, treatment and prevention of cervical spine injury to a certain extent.
ABSTRACT
Objective To investigate the pathological mechanism of spinal injury by axial compression experiment on animal spine, so as to provide references for the treatment, prevention and research of spinal injury. Methods The biomechanical study of rabbit spine segments was performed by axial segment compression experiment. The compression process was recorded and strain analysis was performed by digital image correlation (DIC) technology. Results From the top to the bottom of the spine, the ultimate load and bearing capacity of the segment increased continuously; the average limit load of the corresponding single vertebral body was significantly larger than the segment; the strain of the intervertebral disc in the horizontal and vertical directions was significantly larger than that of the upper and lower vertebral bodies. Conclusions In the process of spine compression, the bearing capacity of the intervertebral disc should be taken into account and the injury of spinal segments is mainly manifested as abnormality of the intervertebral disc. The research findings contribute to the prevention and treatment of spinal compression fractures, as well as the design of related therapeutic instruments and assistive devices.
ABSTRACT
Objective To conduct dynamic impact failure test of rabbit single vertebra, and make comparison with the static compression experiment, so as to study damage mechanism of the vertebral body under the axial impact. Methods The voltage waveform diagram of the force sensor and the detailed process of the vertebral impact were obtained by the oscilloscope and high-speed photography through the drop hammer dynamic impact experimental device. Results The average static load of the thoracic and lumbar vertebra were 910 N and 947 N, respectively; the average dynamic load of the thoracic and lumbar vertebra were 1 196 N and 1 026 N, respectively; the average thoracic and lumbar dynamic load coefficients were 1.37 and 1.08; under static load, the average stress of the thoracic and lumbar vertebra was 15.28 MPa and 12.51 MPa, respectively; under dynamic load, the average stress of the thoracic and lumbar vertebra was 20.03 MPa and 13.56 MPa; during dynamic impact, the mean longitudinal strain and transverse strain was -0.3 and -0.005 (compression); under dynamic conditions, the destruction energy of vertebrae increased from 0 J to 4.4 J. Conclusions Under dynamic and static experimental conditions, the dynamic load of the same vertebral body was greater than that of the static load; the average dynamic load coefficient of the thoracic vertebra was larger than that of the lumbar vertebra; the equivalent stress of the thoracic vertebra was greater than that of the lumbar vertebra; the axial strain of vertebra under impact was greater than the transverse strain; energy growth of the vertebral body presented a slow at first and then a rapid changing process. The research findings can provide some guidance for prevention and rehabilitation of human vertebral body injury in clinic.