Sport injury biomechanics and stress changes in adjacent intervertebral discs after partial discectomies and fusion of the cervical spine

Cervical spine injuries and degeneration of cervical spinal components as well as surgical intervention such as discectomy and fusion are among the major concerns that spinal surgeons have to deal with on a continuous basis. Physico-geometrical and medical considerations taken into account during the surgery will affect the long-term (biomechanical and medical) outcomes of the surgical procedure.; To simulate sport injury mechanisms and the long-term biomechanical effect of the cervical discectomy surgery, two complete 3D Finite Element models (FEM) of the human c-spine (C1-T1) were created.; The first model was a geometrically simplified model that was used to study the vertebrae and disc stresses under high G-z and G-y accelerations while considering the dynamic nature of the forces and visco-elastic properties of the disc and ligaments. The primary results using this model revealed that the stresses in the vertebral bodies, for 10 to 12 G-z accelerations, were under the injury threshold level.; The second complete model was an improved and geometrically detailed nonlinear 3D FE model of the human c-spine (C1-T1). The modeling took into consideration the inhomogeneity and the non-linearity of the hard and soft tissues of the cervical spine. The major components of the c-spine were individually materialized in the second model. The model was validated against existing in-vivo experimental studies. This model was first utilized to investigate sport and accident injuries. The results showed that minimal shear forces and eccentric compression forces could generate enough flexion moment to put the c-spine at the onset of discs injuries and/or clinically instability.; The second model was further utilized to investigate the change in stresses in adjacent discs after partial discectomies and fusion. Discectomy and fusion is a surgical procedure commonly used to correct and/or stabilize an injured or degenerated cervical spine. After fusion, the stresses in adjacent intervertebral discs change and could lead to another surgery. It was determined that the percentage of the contact area between the bone graft and the vertebral body is directly related to the changes in stresses in adjacent discs and to the extent of the bone graft subsidence into the vertebral body.