Arcuate foramen: "Anatomical variation shape or adaptation legacy?"

Assessment of failure risks during C2 vertebra pedicle screw insertion using three-dimensional computed tomography angiography analysis: the role of high-riding vertebral artery and narrow pedicles

BACKGROUND

Cervical fixation is a common treatment for conditions like vertebral fractures, osteosarcoma, osteomyelitis, arthritis, and congenital disorders. The study was designed to assess the occurrence of high-riding vertebral artery (HRVA), narrow C2 pedicles (NC2P) and ponticulus posticus (PP), which pose risks of injuring vertebral artery (VA) during screw placement in cervical fixation procedures.

METHODS

The study examined the prevalence of HRVA, NC2P and PP in 382 pedicle sides of the C2 vertebra using computed tomographic angiography scans. Specific measurements were taken, including the internal height (C2InH), and isthmus height (C2IsH) of C2, as well as NC2P width.

RESULTS

HRVA was identified by specific measurements: C2IsH of ≤ 5 mm and/or C2InHof ≤ 2 mm. NC2P was defined as NC2P width ≤ 4 mm. The reliability between observers and within the same observer, along with the consistency across different software, was assessed. At least one HRVA was found in 9.6% of patients and at least one NC2P in 13% of patients. Females demonstrated higher rates of HRVA and NC2Ps on the left side, with right-side figures at 10.5% and 11.7% for HRVA and NC2Ps respectively, and left side figures at 14.1% for both. Males exhibited a reserve pattern, with higher rates on the right side, marked by 10.3% HRVA and 15% NC2Ps, compared to 5.6% and 11.3% on the left. Furthermore, males showed a significantly higher occurrence of NC2Ps over HRVA on both sides. The presence of PP with NC2Ps detected in 44% of cases, and with HRVA in 16% of cases, a difference found to be statistically significant.

CONCLUSIONS

The digital models incorporating HRVA, NC2P, and PP facilitated a comprehensive analysis of the VA pattern, assessment of the virtual screw trajectory line for VA pedicles, and the designation of specific regions during the procedure, ensuring increased safety planning instrumentation.

Anatomical variations of the atlas arches: prevalence assessment, systematic review and proposition for an updated classification system

Objective and background

This study focuses on the atlas, a pivotal component of the craniovertebral junction, bridging the cranium and spinal column. Notably, variations in its arches are documented globally, necessitating a thorough assessment and categorization due to their significant implications in clinical, diagnostic, functional, and therapeutic contexts. The primary objective is to ascertain the frequency of these anatomical deviations in the atlas arches among a Colombian cohort using cone-beam computed tomography (CBCT).

Methodology

Employing a descriptive, cross-sectional approach, this research scrutinizes the structural intricacies of the atlas arches in CBCT scans. Analytical parameters included sex distribution and the nature of anatomical deviations as per Currarino's classification. Statistical analyses were conducted to identify significant differences, including descriptive statistics and Chi-square tests. A systematic review of the literature was conducted in order to enhance the current Currarino's classification.

Results

The study examined 839 CBCT images, with a nearly equal sex distribution (49.7% female, 50.3% male). Anatomical variations were identified in 26 instances (3%), displaying a higher incidence in females (X2 [(1, N = 839) = 4.0933, p = 0.0430]). The most prevalent variation was Type A (2.5%), followed by Type B (0.4%), and Type G (0.2%) without documenting any other variation. The systematic review yielded 7 studies. A novel classification system for these variations is proposed, considering global prevalence data in the cervical region.

Conclusion

The study highlights a statistically significant predominance of Type A variations in the female subset. Given the critical nature of the craniovertebral junction and supporting evidence, it recommends an amendment to Currarino's classification to better reflect these clinical observations. A thorough study of anatomical variations of the upper cervical spine is relevant as they can impact important functional aspects such as mobility as well as stability. Considering the intricate anatomy of this area and the pivotal function of the atlas, accurately categorizing the variations of its arches is crucial for clinical practice. This classification aids in diagnosis, surgical planning, preventing iatrogenic incidents, and designing rehabilitation strategies.

The morphological classification and clinical significance of atlas vertebral artery sulcus based on computed tomography three-dimensional reconstruction

OBJECTIVE

The purpose of this study was to research the morphological classification and clinical significance of vertebral artery sulcus on atlas based on CT three-dimensional reconstruction.

METHODS

Three-dimensional reconstruction images of 300 adult atlases were collected. A total of 600 atlas vertebral artery sulci were selected in this study. The parameters required for placement of C1 pedicle screw, including depth of grinding drilling (ao), width (cd), length ab), height (H), lateral wall thickness (L1), inner wall thickness (L2), medial angle (∠α), and the cephalad angle to the transverse plane of atlas pedicle (∠β), were measured.

RESULTS

CT three-dimensional reconstruction images showed that there were five types of atlas vertebral artery sulci: no process type (n = 494 cases, 82.33%), upper process type (n = 29, 4.83%), lower process type (n = 25, 4.17%), double process type (n = 19, 3.17%), and posterior ring type (33, 5.50%). One-way ANOVA tests showed that the five groups differed significantly in the parameter of ao, L2, H, ∠α and ∠β. One-way ANOVA with the LSD post hoc tests showed that the parameter ao of the group of no process type was less than that of the group of upper or lower process type (P < 0.05), and ao of the group of lower process or posterior ring type was less than that of the group of the upper type (P < 0.05). The parameter of ao of the male group was larger than that of the female group.

CONCLUSION

No process type of the atlas vertebral artery sulcus was the most common, and the medial angle and cephalad angle of the atlas pedicle in this type were the smallest. When pedicle screws are inserted, the above two angles should not be too large. Male's ao was larger than that of female's. All these findings should be considered to avoid the deviation of the nail track.

CT anatomy of cervical vertebrae of Asian elephant ( Elephas maximus )

Background

Elephants are currently the largest mammals on earth. A comprehensive examination of the anatomy of this animal to diagnose various disorders is required. In addition, due to the heavy head of these animals, adaptations have been made in the anatomical structure of the neck that is worth studying.

Objective

This study aimed to investigate a standard morphologic and morphometric description of the elephant cervical spine. Another aim of this study was to compare the changes in the cervical skeleton of elephants with horses and cattle.

Methods

For this study, the cervical vertebrae of the Asian elephant, cattle and horse were examined. CT Images were obtained using Somatom Spirit II CT Machine. Statistical analysis was done by SPSS 24 software.

Results

Two dorsal tubercles and a groove between them were observed on the dorsal arch of the atlas vertebra of the Asian elephant. In elephant samples, the variation of vertebral body height, spinous process height, transverse process width, vertebral body length and vertebral foramen volume indices were statistically significant. The volume of the vertebral foramen in the elephant decreases in the second vertebra compared to the first vertebra, decreases in the third vertebra, decreases in the fourth, increases in the fifth, decreases in the sixth and increases in the seventh.

Conclusions

In this study, the structure of the cervical vertebrae of the Asian elephant was examined, and certain features were observed. One of the main features was the reduction of the length of the vertebrae, which leads to the decrease of the ratio of neck length to the size of the body. This condition can be due to the high weight of the head in the elephant. To maintain this weight, it is necessary to reduce the length of the neck and confer less mobility.

Anatomical Variations of the Vertebral Artery: Analysis by Three-Dimensional Computed Tomography Angiography in Chinese Population

OBJECTIVE

To analyze the anatomical variations of V3 and V2 segments of the vertebral artery in the Chinese population.

METHODS

The current retrospective study was an observational, anatomical, radiological research. Between 1 January 2018 to 31 December 2019, the data of 589 continuous head-and-neck three-dimensional computed tomography angiography were observed and analyzed using the open-source software of Horos. There were 415 males and 174 females with an average age of 44.63 ± 2.5(18-74) years. The variations of the V3 segment were defined as persistent first intersegmental artery (PFIA) and paracondylar processes (PP). The variations of V2 segments were unusual vertebral artery entrance transverse foreman (UE-V2S) and midline migration (MM). The incidences of all variations were summarized and the gender, side characters were compared.

RESULTS

Among the patients, 4.34% (18/415) males and 4.60% (8/174) females were with the variation of PFIA. Meanwhile, 12.29% (51/415) males and 10.92% (19/174) females were with the variation of PP. Then 18.80% (78/415) males and 16.67% (29/174) females were with UE-V2S. All the variations above were not different in genders. As for the variation of MM, 3.86% (16/415) males and 8.62% (15/174) females were identified, and the difference of genders was significant for this type of variation (P < 0.05). The differences between each side were also observed and analyzed for all variations and no differences were found.

CONCLUSION

There are several variations of V3 and V2 segments of the vertebral artery are associated with the cervical surgeries, most were without differences in genders and sides, except the variation of MM.