Search Results

Cervical spine behavior for generalized loading is often characterized using a full three-dimensional flexibility matrix. While experimental studies have been aimed at determining cervical motion segment behavior, their accuracy and utility have been limited both experimentally and analytically. For example, the nondiagonal terms, describing coupled motions, of the matrices have often been omitted. Flexibility terms have been primarily represented as constants despite the known nonlinear stiffening response of the spine. Moreover, there is presently no study validating the flexibility approach for predicting vertebral motions; nor have the effects of approximations and simplifications to the matrix representations been quantified. Yet, the flexibility matrix currently forms the basis for all multibody dynamics models of cervical spine motion.

Unlike other modes of loading, the tolerance of the human neck in tension depends heavily on the load bearing capabilities of the muscles of the neck. Because of limitations in animal models, human cadaver, and volunteer studies, computational modeling of the cervical spine is the best way to understand the influence of muscle on whole neck tolerance to tension. Muscle forces are a function of the muscle's geometry, constitutive properties, and state of activation. To generate biofidelic responses for muscle, we obtained accurate three-dimensional muscle geometry for 23 pairs of cervical muscles from a combination of human cadaver dissection and 50th percentile male human volunteer magnetic resonance imaging and incorporated those muscles into a computational model of the ligamentous spine that has been previously validated against human cadaver studies.