Some anatomical and morphometric observations in the transverse foramina of the atlas among Kenyans

The transverse foramen, which transmits the vertebral vessels, is the result of special formation of the cervical transverse processes. It is formed by a vestigial costal element fused to the body of the originally true transverse process of the vertebra. In the atlas, where the vertebral artery exits the transverse foramen to enter the cranium, many bony variations have been described, and some are attributable to tortuosity of the vessel, as well as stress forces on the neck. The transverse foramen of the atlas has not been studied in terms of shape, morphometry, presence or absence and bilateral differences. This may shed light on the side differences in neck and vertebra-basilar pathology. A hundred and two atlases obtained from the Osteology Department of National Museums of Kenya were observed for presence, shape and variations of the transverse foramen. Accessory transverse foramina were noted, as well as missing foramina. Anteroposterior and mediolateral diameters of the foramina were taken and the area calculated. Out of the 102 vertebra studied (204 foramina transversaria), 8 incomplete foramina were observed, 6 on the right side and 2 bilateral. There were 4 double transverse foramina observed, 1 on the left and 3 on the right side. All atlases had foramina transversaria. The foramina categorized into types 1 to 5 using a recognized criterion. On the right side, type 4 was predominant (40.2%), while on the left, types 2 and 5 were predominant (39.2% each). Morphometrically, the right and left transverse foramina had mean cross-sectional area of 36.30mm2 and 37.20mm2 respectively. The presence of variations in the foramen transversaria is predominant on the right side. Further, the right foramina have a smaller cross-sectional area. These should be taken into account during posterior cervical approaches, as well as during evaluation of cervicogenic syndromes.Keywords: Atlas vertebrae, transverse foramina, morphometr