THE EFFECT OF DIFFERENT SURGICAL RELEASES ON THORACIC SPINAL MOTION -A CADAVERIC STUDY

Study Design. Two separate experiments (A and B), each involving six h uman cadaveric torsos with intact rib cages and sternums, were done to determine the effect of two different sequences of surgical releases fat T8-T9) on thoracic spinal motion. Objectives. Experiment A was des igned to test the effects of three releases in sequence from anterior to posterior, analogous to a two-stage operative treatment with anteri or and posterior releases. Experiment B, which involved three releases , was designed to determine 1) it unilateral posterior total facetecto my alone allowed a significant increase in motion and 2) if rib head r esection without discectomy allowed a significant increase in motion. Summary of Background Data. In the surgical treatment of thoracic spin al deformity, surgical release is often done to impart additional flex ibility to the spine. Available releases include discectomy, rib head resection, and facetectomy. There is little work to date on the relati ve importance of the disc, rib head, and facet joint in the stability of the thoracic spine. Methods. In experiment A and experiment B, the cadaveric torsos were mounted on a custom-made loading frame. Mechanic al 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). Results. The combin ation of rib head resection and radical discectomy provided the greate st increase in thoracic spinal motion. Standard discectomy alone did n ot 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. Conclusions. These experiments indicate that the combination of rib head resection and radical discectomy may be the optimal thorac ic spinal release.