Partial Lateral Bridges And Supratransverse Foramen In Human Atlas Vertebrae: An Osteological Study In Punjab

ABSTRACT

Background: The lateral outgrowth from the superior articular facet(SAF) to the posterior root of the transverseprocess of the atlas forms the partial lateral bridge(PLB) and when complete forms the supratransverse foramen(STF). Presence of such bridges may predispose to vertebrobasilar insufficiency. Since there are fewer studies onthe lateral bridge therefore the present study was aimed to know the incidence of lateral bridges and STF and alsoto know the dimensions of STF as the knowledge about such dimensions helps in interpretation of radiologicalfindings, provide guidance for neurosurgical intervention.Materials and methods: A total of 80 undamaged, dry human atlas vertebrae were obtained from the Departmentof Anatomy, Government Medical College and SGRDIMSAR, Amritsar, Punjab, India. The Partial lateral bridge(PLB)and Supratransverse Foramen(STF) were identified following the criteria used by Mitchell (1998a, 1998b).Measurements were taken of the maximum dimensions of the STF in (Supero-inferior and Medio-lateral planes)and ipsilateral Foramen Transversarium (FT) in (Ventro-dorsal and Medio-lateral planes). The cross-sectionalarea of STF and ipsilateral FT was calculated.Results: Total 7 (8.75%) lateral bridges in atlas vertebrae occurred. 6 (7.5%) lateral bridges occurred in associationwith the posterior bridges and 1(1.25%) isolated partial lateral bridge occurred on the left side. Partial lateralbridges were found in 2 bones(2.5%) on right side and 4(2.5%)bones on left side. 1 (0.625%) Complete lateralbridges forming STF was observed on right side. Rt. Supra-Transverse Foramen Height (STFH) and Width (STFW)was found to be 5.4mm and 6.2mm. Ipsilateral Foramen Transversarium Length (FTL) and Width (FTW) was foundto be 6.4mm and 5.9mm. The cross-sectional area of Rt. STF was 26.28mm2 and the cross-sectional area ofipsilateral FT was 29.64mm2 and ipsilateral FT area was smaller than STF.Conclusion: The findings in the present study indicate a higher prevalence of lateral bridges on the left side.Difference in the cross sectional area of STF and ipsilateral FT may lead to compression of V.A and this compressionbecomes evidently symptomatic in extreme manipulations of the neck. Patients presenting with vertebrobasilarinsufûciency or cervicogenic syndromes should be evaluated to explore the possibility of the presence of lateralatlas bridges as etiological factor