USE OF CT FOR ANALYSIS OF THE VERTEBRAL FORAMEN IN THE HOSPITAL OF QUERÉTARO USO DE TC PARA ANÁLISE DO FORAME VERTEBRAL NO HOSPITAL DE QUERÉTARO USO DE TC PARA ANÁLISIS DEL FORAMEN VERTEBRAL EN EL HOSPITAL

Objective: To determine the morphology of the vertebral foramen and its distance to the midline. Methods: Twenty cervical CT scans from the radiographic record of 12 men and 8 women, 18 to 74 years old, of C1 to C6 segments were evaluated, measuring the foramen diameter and its distance to the midline. We look for anomalies of vertebral foramen morphology, using Philips Ingenuity CT equipment with Philips IntelliSpace Portal software. Results: The mean age was 47 years; the segment with the most anomalies was C1, with 10% (increase in foramen diameter), followed by C2 and C6, with 5% (vertebral foramen hypotrophy); the mean diameter of the C1 to C6 segment was 6.081 mm, and the median distance from the midline to the vertebral foramen of C2 to C6 was 13.215 mm. The largest diameter of the vertebral foramen was C2, with a mean of 6.67 mm and the smallest was C4, with a mean of 5.75 mm; the greatest distance from the midline to the vertebral foramen was C1, with a mean of 22.59 mm and the shortest was C4, with a mean of 12.13 mm. Conclusions: The mean diameter of the vertebral foramen and its distance to the midline was determined, setting a safety region for procedures. In our city, there is no study that determines the means of the vertebral foramina diameters, the distance from the midline and its anomalies. It is necessary to rely on CT scans and to make a preoperative plan to avoid complications associated with morphological alterations.


INTRODUCTION
3][4][5] In posterior approach surgeries, the rates reported are variable and depend on the instrumentation technique used.They range from 4.1% to 8.2% for transarticular screws (C1-C2), and there are no lesions reported for subaxial lateral mass screws. 6urrently, morphometric evaluations of the cervical pedicles have already been reported in studies involving small numbers of vertebrae in cadavers, as well as in older adults, who, because of their condition, present degenerative changes. 7revious studies include patients with degenerative symptoms of the cervical spine or are specifically focused on the Asian population.
We believe that such data will provide the surgery with an improved understanding of pedicle anatomy and improve decision-making.
Therefore, the purpose of this review is to understand the morphology of the vertebral foramen through operative planning using computed axial tomography, which improves the understanding of the specific morphology of each patient, benefiting preoperative decision making and reducing the risk of a lesion of the vertebral artery.

METHODS
For this study, 20 simple cervical tomographies from the digital radiography archive were evaluated.
Patients with a history of chronic or acute traumatic cervical abnormalities, symptoms suggesting degenerative or inflammatory disease, evidence of infectious or neoplastic conditions, and congenital malformations of the cervical spine were included.
Patients with incomplete or not assessable tomographies were excluded.
An informed consent form was obtained from all the study participants and the study was approved by the Institutional Review Board as registration number (304/17-10-20 VI).
PHILIPS Ingenuity CT equipment and IntelliSpacePortal software were used for all patients, with 3.0 mm helical scans of the cervical spine and reconstruction intervals of 1.5 mm.The scans were performed with the patients in a supine position and the neck in a neutral position.The morphological characteristics were obtained for cervical vertebrae C1 to C6.A total of 12 men and 8 women ranging from 18 to 74 years of age were analyzed.
The program measured the diameter of the vertebral foramen and the distance from the foramen to the midline.We looked for anomalies in the morphology of the vertebral foramen (VF).(Figure 1) The mean age was 47 years.The segment where the most anomalies were found was C1, with 10% (increase in the diameter of the foramen), (Figure 2), followed by C2 and C6, each with 5% (hypotrophy of the vertebral foramen).
The mean diameter of the vertebral foramen of the C1 to C6 segment was 6.081 and the mean distance from the midline to the vertebral foramen of C2 to C6 was 13.215 mm.(Table 1) The vertebral foramen of C2 had the greatest mean diameter at 6.67 mm and of C4, the smallest mean diameter at 5.75 mm.C1 had the greatest mean distance from the midline to the vertebral foramen at 22.59 mm and C4 had the smallest mean distance at 12.13 mm.(Table 1)

DISCUSSION
In this study, the mean diameter of the vertebral foramen and the mean distance from the foramen to the midline were determined, establishing a safety zone for procedures.No study exists for our population that determines the mean of the vertebral foramen and the midline, or their anomalies.It is necessary to have a tomography and to conduct preoperative planning to avoid possible complications associated with morphological changes.

CONCLUSION
At present, there are no studies to determine which is the morphological change most common in the vertebral foramen, in our study it is a decrease in the diameter of the foramen, which could affect the diameter of the vertebral artery, so that a lesion of the foramen and consequently of the contralateral side of said anomaly It was also determined that the mean distance from the vertebral foramen to the midline in the corresponding bodies from C2 to C6 is 13.12 mm, which could be used as a safety range when working with the drill in this area during anterior approach surgery.(Figure 3) Figure 3. Example of anterior approach cervical decompression surgery, after placement of the plate. 9

Figure 1 .
Figure 1.Example of an axial section of C1, showing the measuring of the diameter of the vertebral foramen and the distance from the foramen to the midline. 8

Figure 2 .
Figure 2. Example of a cervical vertebral foramen deformity. 8 USE OF CT FOR ANALYSIS OF THE VERTEBRAL FORAMEN IN THE HOSPITAL OF QUERÉTAROcould have catastrophic consequences, as previously mentioned.

Table 1 .
This table shows the mean diameter of the vertebral foramen at the midline, and the distance from the vertebral foramen to the midline.(Source: Department of Imageology, Digital Radiography Archive of the Hospital General de Querétaro).