Representation of passive spinal element contributions to in vitro flexion-extension using a polynomial model: illustration using the porcine lumbar spine.

A polynomial modeling approach was developed to describe the contribution of individual passive spinal elements to the lumbar spinal motion segment flexion-extension motion. Flexion-extension moment-angle curves from porcine lumbar spines tested using a robotic testing system were described using sixth-order polynomials; the polynomials describing different dissection conditions were subtracted to describe the contribution of individual spinal elements to the motion segment flexion-extension properties. This modeling approach is a powerful and straightforward method for representing the mechanics of individual spinal tissues in biomechanical models and could easily be expanded to incorporate other features such as axial load.