Evaluating the Shape of Foramen Magnum and Overlapping of Occipital Condyle on the Foramen

Objective The objective of this study is to conduct the morphometric analysis of the foramen magnum (FM) and overlapping of occipital condyles on it and also determination of shape of foramen magnum. Method 53 dried human skulls of unknown age and sex were examined from department of Anatomy, Saveetha Dental College and Hospital. Foramen magnum were examined macroscopically for their different shapes. Anteroposterior and transverse diameters was measured using a manual vernier calliper. Also the presence of overlap of occipital condyles was observed. Result The various shapes of foramen magnum observed was egg, oval, hexagonal, pentagonal, circular. Egg shaped foramen was observed in 35.85 %, oval shaped foramen in 26.42 %, hexagonal shaped in foramen magnum in 20.75 %, circular/round shaped foramen in 13 % and pentagonal shaped foramen in 3.77 %. In 72 % of the skull the occipital condyles were observed to protruded into the foramen magnum. The mean antero-posterior and transeverse diameters of the foramen magnum was recorded as 3.822cm and 3.515cm respectively. The mean area of FM was recorded as 11.025 cm2. Conclusion Morphometric analysis of the foramen magnum can be used as supportive findings in estimation of sex of fragmented in- complete or damaged dry human skulls. The knowledge of dimensions of the FM also helpful in determination of malformation (Arnold Chiari Syndrome) and in transcondylar approach to make a safe occipital condyle resection. Though the present study has a limitations as the age and sexes of the skull were not determined, this study may provide an important reference and the measurement may be used as a data for the description of morphological variant of FM.