Morphometric evaluation of the foramen magnum in a Sri Lankan population

R Peiris,A Vadysinghe,D Nanayakkara

doi:10.4038/slaj.v3i2.60

Abstract

Objective: The foramen magnum (FM) that transmits a large number of vital structures is an important anatomical landmark in neurosurgical procedures and forensic anthropology. The aim of the present study was to determine the dimensions and shape of the FM in a Sri Lankan population. Material and method: Forty-four adult skulls (32 males and 12 females) were selected for the study. Sagittal (FMSD) and transverse (FMTD) diameters of the FM were taken using a sliding digital vernier caliper to the nearest 0.01mm by one investigator. The area of the FM was calculated using Radinsky's formula; A=1/4 X 3.14 X FMTD X FMSD and FM index was calculated using the formula: FMTD x 100 / FMSD. The skulls were visually assessed to determine the shape of the FM. The shape of the FM was recorded as round, oval, egg-shaped, tetragonal, pentagonal, hexagonal or irregular. Results: The mean sagittal and transverse diameter, area and index of the foramen magnum in males were 34.62 ±2.17 mm, 29.52±2.13 mm, 695.77±90.64 mm2 and 85.41±5.66, respectively, whereas they were 33.87±2.31 mm, 28.28±1.99 mm, 662.56±98.67 mm2 and 83.69±6.13, respectively, in females. The shape of the foramen was found to be eggshaped in 34.1%, and round in 27.2% of the cases. Conclusions: The size and shape of the foramen magnum are highly variable among different world populations. Sri Lankan skulls showed smaller foramen magnum in compare with those of African, Mediterranean and European populations. Males displayed larger mean values than females for all measured variables.

Highlights

The basicranium forms in a zone of interaction between structures with neural, skeletomotor, respiratory, auditory, masticatory, digestive, and visual functions
The shape of the foramen was found to be eggshaped in 34.1%, and round in 27.2% of the cases
The size and shape of the foramen magnum are highly variable among different world populations

Summary

Introduction

The basicranium forms in a zone of interaction between structures with neural, skeletomotor, respiratory, auditory, masticatory, digestive, and visual functions. Because of the complex structural-functional relationships in the region, the morphology of the basicranium shows compromises resulting from the. The basicranium is complex, and the Foramen Magnum (FM), is the large opening in the posterior part of the cranial base, through which the cranial cavity communicates with the vertebral canal. It is situated at the craniovertebral junction and is oval, and wider behind with its greatest diameter being the anteroposterior [2]. The margin of the FM is slightly overlapped by the occipital condyles which project down to articulate with the superior articular facets on the lateral masses of the atlas [2]

Methods

Results

Conclusion