Neurologic complications after sublaminar wiring. An experimental study in lambs.

To study possible neurologic complications, five lambs were operated on by sublaminar wiring at the thoracolumbar spine. Monitoring of the central motor pathway was carried out by percutaneous electrostimulation. A comparative anatomic study was designed to compare the magnitude of the spinal canal and the area occupied by the spinal cord at the low thoracic and lumbar level in 15 lamb, 8 pig, and 8 human spines. The following parameters were measured by slide caliper: the anteroposterior diameter of the spinal canal and the spinal cord, the length and thickness of the laminas, and the distance between each consecutive lamina. All five operated lambs showed major neurologic deficits after surgery. The results of the anatomic study suggest that there exists in humans a sufficiently ample "safety zone" that permits wire insertion without risking injury to neurologic structures. Such a "safety zone" is nonexistent in lambs and pigs unless an extensive laminectomy is performed to decrease the depth of wire penetration.