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.