Morphological and Morphometric Analysis of Foramen Magnum: An Anatomical Aspect

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To investigate the detailed morphological and morphometric analysis of foramen magnum (FM) in dry cranii.


One hundred fifty skulls of unidentified sex were macroscopically examined and were photographed with Canon 400B (55 mm objective). According to tooth eruption of the skulls, they were accepted as adults. None of the examined skulls showed signs of prior cranial surgery, malformation, or trauma. The evaluated study parameters that were recorded with Vernier caliper in millimeter were as follows: antero-posterior diameter from Basion to Opisthion, transverse diameter (largest distance between the lateral margins of the FM), and the shape of the FM (Fig. 1). The shape of the FM was determined according to FM index that was calculated by dividing antero-posterior diameter by transverse diameter. When FM index was found greater than or equal to 1.2, the foramen was accepted to be oval in shape. Whereas the FM index was found less than 1.2, the foramen was accepted to be round in shape The area of the FM was calculated by using 2 different formulas as described previously by Radinsky (1/4 × π × w × h) and Teixeira (π × {(h + w)/4}2), and “π” was accepted as 3.14 in both formulas.


The results of descriptive statistics and areas of the FMs were presented in Table 1. The mean antero-posterior diameter and transverse diameter of anteroposterior diameter by transverse diameters were found as 34.38 ± 2.38 and 28.95 ± 2.19, respectively. The mean area of the FMs estimated by Teixeria formula was determined significantly larger than the mean area of the FMs estimated by Radinsky formula (P <0.001). According to estimated FM index of the 150 adult dry skulls, 87 (58%) of skulls were described as being round in shape and 63 (42%) of skulls were described as being oval in shape (Fig. 1).


The surgeons must comprehend regarding the detailed morphological and morphometric features of FM to avoid vital complications during the surgical procedures.

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