Entry Point of Pedicle Screw in the Lower Lumbar Spine

Park, Heui Jeon; Rah, Jung Ho; Lee, Doo Hee

Abstract

STUDY DESIGN: We analysed retrospectively the entry point of pedicle screw in the lower lumbar spine using computed tomoscan.
OBJECTIVES
The purpose of this study is to find the ideal entry point of pedicle screw in the lower lumbar spine.
MATERIALS AND METHODS
We evaluated 98 patients with each second, third, fourth, fifth lumbar spine, and divide three group into normal group(NP), osteoarthritis group(OA), degenerative spondylolisthesis group(DS). We collected the two axial images of lower lumbar spine from CT at the same level. One image is parallel to upper end plate and again, the facet joint is well visuable, another image is the pedicle which cross the center, and the size of the both sides of pedicle is same and largest. And then we were superimposed mathematically above two images with computer. With the use of these three images, facet joint and pedicle axis orientation, pedicle isthmus width, distance between facet joint and pedicle axis, distance between lateral surface of facet and pedicle axis are measured. RESULT: The ideal entry point of pedicle screw is 3mm lateral from lateral end of facet joint in NP group, in OA 0.5~1mm medial and in DS 0.3mm medial from lateral end of facet joint.
CONCLUSION
The selected anatomical landmark using the pedicle screw insertion is not advisable because of the variations of pedicle width and orientation depend on pathologic state of the lower lumbar spine, especially facet joint. We suggest that the sugeon should selected well the ideal entry point of the pedicle screw, knowing the shape and any anatomical variations of the pedicle in details before screw insertion with peroperative computed tomoscan.