Biomechanics of the cervical spine Part 2. Cervical spine soft tissue responses and biomechanical modeling.

OBJECTIVE: The responses and contributions of the soft tissue structures of the human neck are described with a focus on mathematical modeling. Spinal ligaments, intervertebral discs, zygapophysial joints, and uncovertebral joints of the cervical spine are included. Finite element modeling approaches have been emphasized. Representative data relevant to the development and execution of the model are discussed. A brief description is given on the functional mechanical role of the soft tissue components. Geometrical characteristics such as length and cross-sectional areas, and material properties such as force-displacement and stress-strain responses, are described for all components. Modeling approaches are discussed for each soft tissue structure. The final discussion emphasizes the normal and abnormal (e.g., degenerative joint disease, iatrogenic alteration, trauma) behaviors of the cervical spine with a focus on all these soft tissue responses. A brief description is provided on the modeling of the developmental biomechanics of the pediatric spine with a focus on soft tissues. Relevance. Experimentally validated models based on accurate geometry, material property, boundary, and loading conditions are useful to delineate the clinical biomechanics of the spine. Both external and internal responses of the various spinal components, a data set not obtainable directly from experiments, can be determined using computational models. Since soft tissues control the complex structural response, an accurate simulation of their anatomic, functional, and biomechanical characteristics is necessary to understand the behavior of the cervical spine under normal and abnormal conditions such as facetectomy, discectomy, laminectomy, and fusion.