A hierarchical approach to finite element modeling of the human spine.
Finite element modeling has become an important part of biomechanics research in the last 30 years. In particular, virtual experimentation on the spine bypasses several limitations on mechanical testing: any load and constraint may be applied to a finite element model, and experiments may be repeated with slight alterations on the same specimen. Because computer power is still limited, each virtual model is designed with a particular scale in mind. To analyze spinal motion, a motion segment consisting of two or more vertebrae and the connective tissue is modeled. For vertebral strength, a single vertebra, with or without posterior elements, is analyzed. To understand the biomechanics of the cancellous bone and to examine bone remodeling, the individual trabeculae comprising the cancellous bone are examined. These three areas represent the bulk of current research. Scientists also explore whole-spine mechanics and ultrastructural dynamics, but these suffer greatly from a lack of physiological data on the observed phenomena. To a large extent, the spinal physiological loading scenario and the load distribution at the different structural levels are unknown. As in vivo measurement techniques and computational power grow, so will the usefulness of finite element modeling.