Morphometry of foramen transversarium and prevalence of accessory transverse foramina in the cervical spine of an adult Kenyan population: An osteological study

Abstract

Introduction: The foramen transversaria (FT) are unique to the transverse processes of the cervical vertebrae. They normally transmit the second part of the vertebral artery, the vertebral vein and sympathetic nerves with the exception of the seventh cervical vertebrae foramen transversarium that transmits the vertebral vein only. Published data indicate that the foramina transversaria exhibit several variations in their size, number, shape, and maybe present or absent. These variations could raise concerns about the integrity of the structures that traverse them and bring up the possibility of an extraosseous course of the vertebral artery. There is need for more information on foramen transversaria variations to improve surgical and patient outcomes. Objective: To describe the morphometry of foramen transversaria and determine the prevalence of accessory foramen transversaria in intact dried cervical vertebrae of Kenyan population. Methods: This was a descriptive, cross-sectional anatomical study done on 224 dried cervical vertebrae archived at the National Museums of Kenya. Dried intact adult skeletons that met the eligibility criteria were purposively sampled to saturation. Morphometric measurements (anteroposterior and transverse diameters) were obtained using a 150 mm steel ruler. Accessory foramen transversaria were noted, photographed and documented on a structured data collection sheet. Descriptive statistical analysis techniques of frequency (with corresponding proportions), mean (with corresponding standard deviation), median (with corresponding interquartile range) were used to describe the study participants and outcomes. A student t-test was conducted to compare the statistical difference in the means of the left and right transverse and anteroposterior diameters. Results: This study reviewed 224 dried cervical vertebrae of which 47 had accessory foramen transversaria and 1 was missing foramen transversaria bilaterally. The prevalence of accessory foramen transversarium was 21% of the cervical vertebrae sampled and 55.3% (n=26) of these were unilateral while 44.7% (n=21) were bilateral. The overall mean anteroposterior (AP) diameter of foramen transversarium was 5.333 ± 1.218 mm while on the right it was 5.348 ± 1.273 mm and 5.365 ± 1.212 mm on the left. The overall mean transverse diameter was 5.703 ± 1.129 mm, while the mean right transverse diameter of foramen transversaria was 5.590 ± 1.195 mm and 5.868 ± 1.132 mm on the left. There was a statistically significant difference in the left and right mean transverse diameter of C3 (p=0.044) and C5 (p=0.043) as well as the mean anterior posterior diameter of C3 (p=0.015) and C6 (p=0.040). A single (0.5%) cervical vertebra (C7) exhibited bilateral absence of foramen transversaria. No unilateral absence of FT was noted. The most common shape of foramen transversarium was round (51.3%) followed by oval (43.3%) and irregular (4.9%). Conclusions: The prevalence of accessory foramina is high. It indicates an anomalous course of the vertebral artery; that requires consideration by orthopedic and spine surgeons in the care of patients with cervical spine diseases.