The internal carotid artery and the atlas: anatomical relationship and implications for C1 lateral mass fixation

Abdominal Arterial Translation in Lower Lumbar Spine Level Due to Positional Change: A Clinical Survey Using Intraoperative Computed Tomography

Background: Abdominal vascular injury, a fatal complication of lumbar disc surgery, should concern spine surgeons. This study aimed to compare the position of the abdominal arteries in the supine and prone positions and the factors involved. Thirty patients who underwent lumbar surgery by posterior approach were included. Methods: All patients underwent computed tomography (CT) preoperatively in the supine position and intraoperatively in the prone position. In the CT axial image, at the L4, L4/5 disc, L5, and L5/S1 disc level, we measured the shortest distance between the abdominal arteries and the vertebral body (SDA: shortest distance to the aorta), and the amount of abdominal arterial translation, defined as "SDA on intraoperative CT" minus "SDA on preoperative CT". Additionally, the preoperative CT axial images were evaluated for the presence of aortic calcification. Results: No significant difference in SDA values based on patients' positions was observed at each level. In males, the supine position brought the abdominal artery significantly closer to the spine at the left side of the L5/S level (p = 0.037), and, in cases of calcification of the abdominal artery, the abdominal artery was found to be closer to the spine at the left side of the L4/5 level (p = 0.026). Conclusions: It is important to confirm preoperative images correctly to prevent great vessel injuries in lumbar spine surgery using a posterior approach.

Morphometric analysis of dry atlas vertebrae in a northeastern Thai population and possible correlation with sex

PURPOSE

The uppermost segment of the cervical vertebra or atlas (C1) is a critically important anatomical structure, housing the medulla oblongata and containing the grooves for the C1 spinal nerve and the vertebral vessels. Variations of the C1 vertebra can affect upper spine stability, and morphometric parameters have been reported to differ by population. However, there are few data regarding these parameters in Thais. The use of this bone to predict sex and age has never been reported.

METHODS

This study aimed to examine C1 morphometry and determine its ability to predict sex. Twelve diameter parameters were taken from the C1 vertebrae of identified skeletons (n = 104, males [n, 54], females [n, 50]). Correlation analysis was also performed for sex and age, which were predicted using machine learning algorithms.

RESULTS

The results showed that 8 of the 12 measured parameters were significantly longer in the male atlas (p < 0.05), while the remaining 4 (distance between both medial-most edges of the transverse foramen, transverse dimension of the superior articular surface, frontal plane passing through the canal's midpoint, and anteroposterior dimension of the inferior articular surface) did not differ significantly by sex. There was no statistically significant difference in these parameters on the lateral side. The decision stump classifier was trained on C1 parameters, and the resulting model could predict sex with 82.6% accuracy (root mean square error = 0.38).

CONCLUSION

Assertation of the morphometric parameters of the atlas is important for preoperative assessment, especially for the treatment of atlas dislocation. Our findings also highlighted the potential use of atlas measurements for sex prediction.

Strategies to avoid internal carotid artery injury in “sandwich” atlantoaxial dislocation patients during surgery

PURPOSE

To elucidate the anatomic relationship between the internal carotid artery (ICA) and the bony structures of the craniovertebral junction among "sandwich" atlantoaxial dislocation (AAD) patients, and to analyze the risks of injury during surgical procedures.

METHODS

The distance from the medial wall of ICA to the midsagittal plane (D1), the shortest distance between the ICA wall and the anterior cortex of the lateral mass of atlas (LMA) (D2) on the most caudal and cranial levels of LMA and the angle (A) between the sagittal plane passing through the screw entry point of C1 lateral mass(C1LM) screw and the medial tangent line of the vessel passing through the entry point were measured. Besides, the location of ICA in front of the atlantoaxial vertebra was divided into 4 categories (Z1-Z4).

RESULTS

There was a statistically difference between the male and female patients regarding D1, and the difference between D2 at level a and level b as well as angle A between the left and right sides were statistically different (p < 0.05). Ninety-two ICAs (57.5%) were anteriorly located in Z3, 50 (31.3%) were located in Z4, 17 were located in Z2, and only one ICA was located in Z1 in all 80 patients.

CONCLUSIONS

In "sandwich" AAD patients, particular attention should be paid to excessively medialized ICA to avoid ICA injury during trans-oral procedures, and the risk of injuring the ICA with more cranially and medially angulated C1LM screw placement was relatively less during posterior fixation procedures. A novel classification of ICA location was used to describe the relationship between ICA and LMA.

Cervical Spine Navigation and Enabled Robotics: A New Frontier in Minimally Invasive Surgery

Background: Robotic-assisted and computer-assisted navigation (CAN) systems utilization has been rapidly increasing in recent years. Most existing data using these systems are performed in the thoracic, lumbar, and sacral spine. The unique anatomy of the cervical spine maybe where these technologies have the greatest potential. To date, the role of navigation-enabled robotics in the cervical spine remains in its early stages of development and study. Purpose: This review article describes the early experience, case descriptions and technical considerations with cervical spine screw fixation and decompression using CAN and robotic-assisted surgery. Methods: Representative cervical cases with early surgical experience with cervical and robotic assisted surgery with CAN. Surgical set up, technique considerations, instrumentation, screw accuracy and screw placement were elevated and recorded for each representative cervical case. Results: Existing robotic assisted spine surgical systems are reviewed as they pertain to the cervical spine. Method for cervical reference and positioning on radiolucent Mayfield tongs are presented. C1 lateral mass, odontoid fracture fixation, C2 pedicle, translaminar, subaxial lateral mass, mid cervical pedicle, navigated decompression and ACDF cases and techniques are presented. Conclusion: In conclusion, within the last several years, the use of CANs in spinal surgery has grown and the cervical spine shows the greatest potential. Several robotic systems have had FDA clearance for use in the spine, but such use requires simultaneous intraoperative fluoroscopic confirmation. In the coming years, this recommendation will likely be dropped as accuracy improves.