Absence of costal element of the foramen transversarium of atlas vertebrae

Abstract

INTRODUCTIONFirst cervical vertebra, i.e. the atlas is ring shaped, with an anterior arch, a posterior arch and two lateral masses. Its transverse processes are large, projecting out laterally and downwards from the lateral masses, they are long, and their anterior and posterior tubercles are fused into one mass. Each transverse process bears a foramen known as foramen transversarium (Figure 1).The second part of the vertebral artery traverses through this foramen before entering the occipital triangle and then the cranial cavity. Many bony variations have been described by different authors.1-3 Scanty literature is available on the absence of costal element of the first cervical vertebra and its impact on the clinical anatomy of this region. Therefore, a study was conducted on fifty atlas vertebrae to look for absence of costal element of foramen transversarium. METHODSFifty dry atlas vertebrae of adult size of unknown sex but of a mixed North Indian population were obtained from the department of Anatomy, University College of Medical Sciences and GTB Hospital, for the present study. Broken or incomplete atlases were excluded from the study. Presence or absence of foramen transversarium was grossly looked for and the boundaries carefully noted in hundred transverse processes of 50 atlas vertebrae. ABSTRACT Background:Since scanty literature is available on the absence of costal element forming foramen transversarium of atlas vertebra therefore this study was undertaken. Atlas vertebrae were examined to see the presence of foramen transversarium and their boundaries. Methods: Hundred foramina transversaria of 50 atlas vertebrae were examined grossly. Results: Foramen transversarium was seen to be present in all the transverse processes of the atlas vertebrae examined. Costal element was found to be missing in seven foramina tranversaria out of 100 foramina seen. It was found to be absent on the right side in three vertebrae and in two it was absent bilaterally. Conclusions:In case the costal element of the foramen transversarium is absent, the second part of vertebral artery passing through this foramen is liable to be damaged while operating at the level of atlanto-occipital joint the operating surgeon should be aware of such variations so as to avoid injury of second part of vertebral artery and subsequently preventing any kind of neurological involvement. Radiologists must also know about such variations so as to correctly interpret radiological image of the craniovertebral region.

Study on the Morphological Variations of the Adult Human Atlas Vertebrae

“…Anterior margin of the foramen transversarium was absent on the right side in three cases out of 100 foramina transversaria (3%). This margin was absent bilaterally in two cases out of 100 foramina seen (2%) [8]. Unilateral absence of foramen transversarium, on the left side has been reported by Vasudeva and Kumar.…”

Study of Human Atlas Vertebrae for the Presence of Retroarticular Groove or Canal in North Indians

“…A number of studies have been conducted on atlas vertebrae but little is done for incidence of retroarticular groove or foramina [12]. Retroarticular grooves or canals cause compression of artery during extreme rotator movement of neck or during surgery causing cerebrovascular incidents [13].…”

Atlas occipitalisation associated with other anomalies in a 16th century skeleton from Sardinia (Italy)

“…Recent studies demonstrated an incidence of absence of the costal element ranging from 2% [4] to 10% [18]; in unilateral defects there is a prevalence for the right side. This variation is attributed to a developmental defect or to variations in the course of the vertebral artery and should be considered in modern clinical practice as it may expose the vertebral vessels to the risk of being damaged [4].…”