Basic Study And Application Of Percutaneous Pedicle Screw In Minimally Invasive Spinal Surgery

To provide minimally invasive spinal surgery with the anatomical basis for the percutaneous pedicle screw. The origin,branch and distribution of the posterior rami of spinal nerves and the dorsal branches of the segmental artery,vein in the thoracolumbar region were observed on 10 adult specimens. The posterior branch of the segmental artery in the thoracolumbar region asises lateral to the intervertebral foramen and runs dorsocaudal,inferior to the superior articular process of the vertebral below,and the dorsal branchs of the segmental veins parallel their corresponding arteries.The posterior rami emerge from the intervertebral foramen posterior to the superior articular process of the vertebral below,and divide into their terminal medial and lateral branchs.The medial branch of the posterior ramus of the spinal nerve courses dorsally from the lateral aspect of the superior articular process to the root of the transverse,and it is attached to the periosteum by fibers,and the lateral one enters into the deep muscles of the the back. Only the percutaneous pedicle screw can we avoid mechanical damage to the posterior ramus of the spinal nerve as well as intraopretive bleeding that may require cautery.To derive theoretical accuracy requirements for spinal pedicle screw placement without navigation system. A geometric model was developed relating spinal pedicle anatomy to accuracy requirements for pedicle screw insertion without navigation system.This model was used to derive error tolerances for pedicle screw placement when using clinically relevant screw diameters in thoracolumbar spine (6.5 mm ; 6.0mm or 5.5mm).The error tolerances were represented as the permissible rotational and translational deviations from the ideal screw trajectory that would avoid pedicle wall perforation. As anticipated, accuracy requirements were greatest at spinal levels where the relevant screw diameter approximated the dimensions of the pedicle. The translational deviation requirements were highest for T12 followed in descending order by T11, L1, L2,L3 and the rotational deviation requirements were highest for L1 followed in descending order by T12, T11, L2,L3 in thoracolumbar spine with the pedicle screwdiameter 6.5mm. These results demonstrate that extremely high accuracy is necessary for the pedicle screw insertion at certain levels of the spine without perforating the pedicle wall. The relevant dimensions of the pedicle and the distance from entry point to ismuths should be measured before operation for these accuracy requirements .The use of pedicle screws for spinal stabilization has become increasingly popular worldwide. Pedicle screw systems engage all three columns of the spine and can resist motion in all planes. Several studies suggest that pedicle screw fixation is a safe and effective treatment for many spinal disorders. Standard techniques for pedicle screw placement, however, require extensive tissue dissection to expose entry points and to provide for lateral-to-medial orientation for optimal screw trajectory. Open pedicle fixation and spinal fusion have been associated with extensive blood loss, lengthy hospital stays, and significant cost. The purpose of this paper is to describe a new technique and instrumentation designed by the research team for minimally invasive posterior fixation of the thoracolumbar spine by using percutaneous screws and rods. Our initial clinical experience will also be included. Although percutaneous lumbar pedicle screw insertion has been previously reported, a minimally invasive approach to inserting a longitudinal connector for these screws and treating thoracolumbar fracture has proven more challenging. An cannula pedicle screw system was designed so that screws could be placed percutaneously by using a guided K-wire that would allow for manipulation of the angular screw-rod conjunction and reduction of the injured segment . The insertion of the rod can be placed through a small wound. Because the thoracolumbar spine is more nearly to the skin than other segments and the rod...