Abstract
Spinal fixation is a common surgical method to stabilize the unstable spines using internal devices. However, excessive intervertebral motions and stresses of adjacent segments are produced. The potential use of dynamic stabilization as a novel approach to spinal fixation is currently being investigated. In this study, the virtual biomechanical test of a new spinal fixation instrument for dynamic stabilization was presented. Finite element models of an intact lumbar spine and two spinal fixations using Ti rods and SMA springs were developed. The intersegmental rotation, ligament tension force, contact force on the facet joint, and the von Mises stress on the intervertebral disc were predicted under the flexion and extension. The results showed that the spinal motion could be recovered and the maximum von Mises stress levels on the intervetebral disc, ligament tension force, and the contact force on the facet joint could be greatly reduced at the adjacent segments in the dynamic stabilization using the SMA springs in comparison with those in the rigid fixation using the Ti rods. This result agrees with the clinical experience and indicates that the spinal fixation under dynamic stabilization was more clinically appropriate. Moreover, the virtual biomechanical test technology can provide a useful tool for not only the decision of the surgical options in spinal fixation but also the development of new medical implants.
