Posterior element loads in lumbar motion segments.

This report concerns the manner in which the intervertebral disc and the posterior elements share loads placed on a lumbar motion segment. A two-dimensional biomechanical model was used to examine this. The model incorporated two rigid bodies to represent the vertebrae and six elastic springs to represent the tissues of the intervertebral disc and the posterior elements. Compression loads were resisted almost totally by the model intervertebral disc, but both the intervertebral disc and the posterior elements contributed substantially to resisting anteroposterior shear and flexion-extension loads. Motion segment morphology was a major determinant of load-sharing in model response to anteroposterior shear.