Morphometric analysis of the foramen magnum in a sample of adult Sri Lankan skulls

The foramen magnum (FM) that transmits a large number of vital structures is an important anatomical landmark in neurosurgical procedures and forensic anthropology. The objective of the present study was to determine the dimensions and shape of the FM in a sample of adult Sri Lankan skulls. Forty-four adult skulls (32male and 12female) were selected for the study. The sagittal (FMSD) and transverse (FMTD) diameters of the FM were measured 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=1/4×3.14×FMTD×FMSD and the index was calculated using the formula: FMTD×100/FMSD. The skulls were visually assessed to determine the shape of the FM. The shape of the FM was recorded as round, oval, eggshaped, pentagonal, hexagonal or irregular. The mean sagittal and transverse diameter, area and index of FM in males were 34.62±2.17mm, 29.52±2.13mm, 695.77±90.64mm2 and 85.41±5.66 respectively, whereas they were 33.87±2.31mm, 28.28±1,99mm, 662.56±98.67mm2 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 cases. The size and shape of the FM are highly variable among different world populations. Skulls in the studied sample showed smaller FM in comparison with those of African, Mediterranean and European populations. Males displayed larger mean values than females for all measured variables. Morphometric analysis of the foramen magnum in a sample of adult Sri Lankan skulls