The effect of different surgical releases on thoracic spinal motion. A cadaveric study

Two separate experiments (A and B), each involving six human cadaveric torsos with intact rib cages and sternums, were done to determine the effect of two different sequences of surgical releases (at T8-T9) on thoracic spinal motion.

Experiment A was designed to test the effects of three releases in sequence from anterior to posterior, analogous to a two-stage operative treatment with anterior and posterior releases. Experiment B, which involved three releases, was designed to determine 1) if unilateral posterior total facetectomy alone allowed a significant increase in motion and 2) if rib head resection without discectomy allowed a significant increase in motion.

In the surgical treatment of thoracic spinal deformity, surgical release is often done to impart additional flexibility to the spine. Available releases include discectomy, rib head resection, and facetectomy. There is little work to date on the relative importance of the disc, rib head, and facet joint in the stability of the thoracic spine.

In experiment A and experiment B, the cadaveric torsos were mounted on a custom-made loading frame. Mechanical testing (using weights, pulleys, and digital goniometers) was done after each surgical release to measure the extent of angular rotation in the coronal plane (right lateral bending and left lateral bending) and in the sagittal plane (flexion and extension).

The combination of rib head resection and radical discectomy provided the greatest increase in thoracic spinal motion. Standard discectomy alone did not allow a significant increase in motion. Rib head resection without discectomy did not allow a significant increase in motion. Unilateral posterior total facet excision did not allow a significant increase in motion.

These experiments indicate that the combination of rib head resection and radical discectomy may be the optimal thoracic spinal release.