Lumbar pedicle: surgical anatomic evaluation and relationships

Abstract

IntroductionTranspedicular screw fixation can be used for the treatment of unstable lumbar spine caused by trauma, tumors, infections, and degenerative conditions. Instrumentation techniques of the spine using the pedicle from posterior into the vertebral body have become popular recently, because of the advantages of these systems [1, 3,4,5,6,10,11,12,13]. Pedicle screw placement does not pose the same high risk of damage to the spinal cord, dural sac, and nerve roots in the lumbar region as it does in thoracic and cervical spine. However, accurate anatomic knowledge is needed to perform a safe surgical intervention in the lumbar region [2,9,11]. Despite the growing interest in pedicle instrumentation in the lumbar spine, the anatomic relationships of lumbar pedicle have not yet been analyzed adequately for the safe performance of these clinical applications. Even though some of the measurements duplicate previous studies, and the data presented in this study are limited to the surrounding tissues of the pedicle, we consider such that information is necessary for building Abstract Although several clinical applications of transpedicular screw fixation in the lumbar spine have been documented for many years, few anatomic studies concerning the lumbar pedicle and adjacent neural structures have been published. The lumbar pedicle and its relationships to adjacent neural structures were investigated through an anatomic study. Our objective is to highlight important considerations in performing transpedicular screw fixation in the lumbar spine. Twenty cadavers were used for observation of the lumbar pedicle and its relations. After removal of whole posterior bony elements including spinous processes, laminae, lateral masses, and inferior and superior facets, the isthmus of the pedicle was exposed. Pedicle width and height (PW and PH), interpedicular distance (IPD), pedicle-inferior nerve root distance (PIRD), pedicle-superior nerve root distance (PSRD), pedicle-dural sac distance (PDSD), root exit angle (REA), and nerve root diameter (NRD) were measured. The results indicated that the average distance from the lumbar pedicle to the adjacent nerve roots superiorly, inferiorly and to the dural sac medially at all levels ranged from 2.9 to 6.2 mm, 0.8 to 2.8 mm, and 0.9 to 2.1 mm, respectively. The mean PH and PW at L1-L5 ranged from 10.4 to 18.2 mm and 5.9 to 23.8 mm, respectively. The IPD gradually increased from L1 to L5. The mean REA increased consistently from 35°to 39°. The NRD was between 3.3 and 3.9 mm. Levels of significance were shown for the P<0.05 and P<0.01 levels. On the basis of this study, we can say that improper placement of the pedicle screw medially and inferiorly should be avoided.

Postoperative computed tomography assessment of pedicle screw placement accuracy

“…Although successful and encouraging results have been presented in some studies, the complications which may emerge during surgery can be very serious. Reported studies are few in this area, and the true incidence of complications is not certain; it may be much higher than current estimates, owing to possible under-reporting (8).…”

“…This was because of the anatomy of the pedicle (8). In our study, the superior and inferior walls were not penetrated.…”

“…Although instrumentation techniques of the spine, using the pedicle as a source of purchase from posterior into the vertebral body, have become an increasingly popular form of spinal fixation, they are not without complications. Relevant studies present the potential risk of damaging the nerve roots, dural sac, vascular structures, and pleura as a major limitation of pedicle screw instrumentation in lumbar spine (4,8,22).…”

“…However, accurate anatomic knowledge is needed to perform a safe surgical intervention in the lumbar region (8).…”

“…Further, the accuracy of pedicle screw insertion is crucial for the efficiency and stability of the surgical procedure (5,10). For accuracy, pedicle screw instrumentation may be guided by anatomic landmarks, preoperative imaging, and intraoperative imaging tools such as plain radiography, fluoroscopy, and, more recently, image-guided technology (3,4,5,8,12,18,21,22).…”