MATHEMATICAL ANALYSIS AND OPTIMIZATION OF DESIGN CHARACTERISTICS OF STABILIZING VERTEBRAL BODY REPLACING SYSTEMS FOR SUBAXIAL CERVICAL FUSION USING THE FINITE ELEMENT METHOD

Objective. To analyze the characteristics of the stress-strain state of the cervical spine when replacing vertebral body with implants of different design. Material and Methods. Mathematical modeling was performed by developing three finite element models of the cervical spine. The models simulated human cervical spine within C3–C7 spinal segment. The C5 vertebra was replaced by three different systems: mesh cage, mesh cage combined with anterior plate, and telescopic vertebral body replacement implant fixed to the bodies. The stress-strain state of models was studied under four variants of loading: compression, flexion, extension, and rotary impact. Results. Stress intensity values were obtained for the following structures: top of the vertebral body, bottom of the vertebral body, pedicle, lamina, joint masses, teeth and screws (if any) of instrumentation under different loading options. Conclusion. The presence of an additional fixation to vertebral bodies allows reducing the level of maximum stress in the bone tissue of vertebrae contacting the implant. Telescopic cage shows the lowest level of stress in the model elements under compression and flexion. Stress indicators in extension and rotation have minor differences between different sites.