A Morphological study of Shapes, Overlapping of Occipital Condyles and the Anterior Tubercle of Foramen Magnum in Human Skull with Comparison in Adolescent, Adult and Foetal age and in Males and Females

Introduction: Foramen Magnum (FM) transmits many important structures. Standard literature states this foramen to be roughly oval shaped. However, recent researches suggest that the FM can of varied shapes. The FM can be overlapped by occipital condyles causing hindrance for the traversing structures. Rarely the FM shows a tubercle at its anterior end, which can also cause problems for the traversing structures. Aim of study: 1. To observe different shapes of the FM and their frequency 2. To observe frequency of overlapping of occipital condyles on the FM 3. To observe the frequency of a rare tubercle at the anterior end of FM Materials and methods: 181 adult skulls (known sex) and 54 foetal skulls (total 235), were studied from different medical institutes in India. These skulls were arranged in Foetal (A), Adolescent Female (B-f), Adolescent Male (B-m), Adult Female (C-f) and Adult Male (C-m) groups. Results: The FM had the following shapes overall (percentage wise) Circular 13.2%, Oval 16.6%, Egg Shaped 18.3%, Rhomboid 14%, Pentagonal 5.95%, Hexagonal 15.3%, Heptagonal 4.6%, and Irregular 11.9% Overall, the occipital condyles overlapped the FM in 21.27% cases; most frequently in oval shaped FM. Given, percentage wise occurrence for each group: A group- 00%, B-f group- 23.07%, B-m group- 15.9%, C-f group- 44.1%, and C-m group- 28.5% 10.63% of the FM had the anterior tubercle, most frequent in oval shaped FM. Given, percentage wise occurrence in each group: A group- 00%, B-f group- 15.38%, B-m group- 13.63%, C-f group- 14.7%, and C-m group- 11.6%.