Anatomy of subaxial cervical foramens: the safety zone for lateral mass screwing

Abstract

AbstractsIntroduction The purpose of this study was to measure the structures of the ventral of lateral masses using cadaver specimens and to quantitatively compare the safety zone for the two major techniques used on each vertebral level from C3 to C6. Methods This study is based on 52 cervical vertebrae of 13 cadavers. The anatomical measurements focused on the anterior surface of the lateral mass. We investigated the safety width, heights, and the height of nerve roots. Results The mean values of the safety width of the Magerl technique from C3 to C6 were 6.1, 7.3, 6.4 and 4.3 mm, respectively. The mean values of the safety width of the Roy-Camille technique were 6.7, 6.6, 5.8 and 5.4 mm, respectively. The mean values of the safety height of the Magerl technique were 5.0, 5.4, 5.8 and 5.2 mm, respectively. The mean values of the safety height of the Roy-Camille technique were 4.9, 4.0, 1.0 and -1.2 mm, respectively. The mean values of the nerve root height were 3.9, 4.9, 5.9 and 6.9 mm, respectively. Conclusion The safety width of the Magerl technique was shorter at C6 because the vertebral artery runs more laterally at C6. The height for the Magerl technique was not significantly different from C3 to C6, however, the safety height for the Roy-Camille technique was significantly shorter at C5 and C6. Our findings suggest that it is important to ensure that the screw(s) penetrate through the cranial side of the ventral aspect of a lateral mass when performing the Magerl technique at all vertebral levels, and to carefully select the screw length when using the RoyCamille technique, especially at C5 and C6, in order to avoid nerve root injury.

An analysis of the anatomic features of the cervical spine using computed tomography to select safer screw insertion techniques

“…Morphometric studies using cadavers [11][12][13][14][15] have been reported, which noted the quantitative three-dimensional anatomy of middle cervical regions with measurements of the vertebral bodies, spinal canal, pedicles, lateral masses and transverse foramen. With advances in imaging technology, multiplanar reconstructed CT scans now enable the desired morphology of the cervical spine to be analyzed in three dimensions.…”

Is the Vertebral Posterior Line a Safety Landmark for Cervical Posterior Screw Insertion? – Radiological Study of the Vertebral Artery in the Cervical Spine

“…As the placement of such screws may result in VA injury, the location of the VA in the cervical spine must be identified. Although Nishinome et al 3) examined the safety zone for lateral mass screws in 13 cadavers, they did not address the safe distance between the posterior VA surface and the anterior aspect of the lateral mass. Ebraheim et al 2) reported that VA injury can be avoided by screwing perpendicular to the posterior aspect of the lateral mass at C3-C5 and 10° lateral to the sagittal plane at C6 starting at the lateral mass midpoint.…”

“…Although the risk for VA injury is lower than upon the insertion of pedicle screws, when lateral mass-or transarticular screws are too long or incorrectly directed, the VA may be injured because the vessel is located close to the front of the lateral mass. [1][2][3] Intraoperative lateral Neurologia medico-chirurgica Advance Publication Date: March 5, 2020 perpendicular distance between the posterior VA surface and the posterior line of the vertebral body in 105 patients. We also examined the impact of VA anomalies on the usefulness of the safety line in patients subjected to the insertion of cervical posterior lateral mass-or transarticular screws.…”

Four lateral mass screw fixation techniques in lower cervical spine following laminectomy: a finite element analysis study of stress distribution

“…In fact, all LSF techniques may result to diverse complications, depending on the surgeon’s optimization of the LSF techniques [ 4 , 5 ]. For the last two decades, many studies have evaluated the advantages of different LSF techniques, based on its complications [ 6 - 8 ]. However, we are unaware of any report that directly compares LSF techniques by analyzing fixation fractures as a severe complication -- which has a relatively low incident rate [ 9 , 10 ].…”