In the treatment of intractable pain, CT-guided cordotomy is an option in specially selected cases with malignancy. In this study, anatomic and technical details of the procedure and the experience gained from treating 207 patients over a 20-year period are discussed.

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This study indicates that improper placement of the pedicle screw medially and superiorly in the middle and lower cervical spine should be avoided and that the anatomic variations between individuals should be established by measurement.

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.

Object. The cervical uncinate processes (UPs), their variations, and the relationships between the neurovascular structures and surrounding bone were investigated in this anatomical study. The object of this study was to highlight the important surgery-related considerations associated with ventral, ventrolateral, and posterior decompressive surgery. Methods. Forty-nine adult C3–7 dry bone samples were used, and 10 measurements were obtained for each vertebra. The anterior measurements involved the cervical uncinate process (UP): height, width, length, distance between its tip and vertebral foramina, interuncinate process distance, sagittal angle with the superior margin of the vertebral body (VB), VB anteroposterior diameter, and VB width. Posterior measurements involved the vertical distance between the superior border of the lamina at the lamina—facet joint and the tip of the UP, as well as the horizontal distance between the medial-most border of the superior facet and the tip of the UP. All symmetrical structures were measured bilaterally. There were no statistically significant differences between right- and left-sided measurements in this series. The height of the UP increased gradually at each segmental level between C-3 and C-7. The width of the UP did not change with segmental level (5.0 mm at C-3 compared with 5.3 mm at C-7). On average, the length of the UP was relatively constant. The distance from the tip of the UP to vertebral foramina averaged 1 mm at the C2–3 level and 1.5 mm at the C5–6 level. Interuncinate distance and VB width gradually increased and were highly variable, which appeared to be related with osteophyte formation. There was a slight gradual increase from C-3 to lower segments, and it paralleled with the midline anteroposterior diameter of the same VB. The angle between the UP and the superior margin of the VB exhibited great variety. The posterior measurements decreased gradually from C-3 to C-7. Conclusions. Based on the data obtained in this study, a surgeon is provided with a three-dimensional orientation as well as anatomical knowledge. This knowledge also allows for a more effective neurovascular decompression by minimizing the surgery-related complications.

In each hemisphere, the vascularization pattern of the distal ACA is different to a greater or lesser extent. An awareness of this fact will contribute significantly to surgical interventions.

The fossa navicularis is a relatively rare anatomic variation of the skull base. Awareness of its existence will avoid misinterpretations of radiological images and unnecessary investigations. This study describes the appearance of the fossa navicularis, and investigates its incidence and whether it is related to pathology at the basiocciput. We studied 492 dry human skulls and 525 computer tomography (CT) images of patients. Dry skulls showing a fossa navicularis were investigated by CT scan, whereas patients identified as having a fossa navicularis were further examined with magnetic resonance imaging (MRI). To document the position of the fossa more precisely, measurements were made between the fossa navicularis and certain anatomic landmarks such as the foramen ovale, the pharyngeal tubercle, the posterior border of the vomer, the foramen lacerum, the carotid canal, and the occipital condyle. Upon examination, 26 of 492 skulls (5.3%) were found to have a fossa navicularis. Twelve were <2 mm in depth and the other 14 had a depth of >/=2 mm. Of the 525 patients, 16 (3.0%) were identified as having a fossa navicularis in CT images. Evaluation of MRIs showed no soft tissue lesions in any of these patients. Comprehensive anatomic details of the fossa navicularis have not been reported in the literature. The results of this study may be useful to radiologists, anatomists, and surgeons interested in the skull base.

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