DOI: 10.5061/dryad.5qfttdz8w
title: Morphometric analysis of the foramen magnum in sex determination: An additional 3DCT study from Nepal on a larger sample

description: Background: Determination of sex of the skeletal remains plays a vital
 part in the identification of an individual. This study is focused on the
 morphometric measurement of the foramen magnum region and examining the
 accuracy of sexual dimorphism in the Nepalese population. 
   Methods: Measurements were obtained from 3D computed tomography
 (CT) scan of 261 Nepalese adult cranial bases with known age and sex.
 Length and breadth of the foramen magnum, length and breadth of right and
 left occipital condyles and maximum and minimum intercondylar distance
 were measured on the base of the skull CT images. Results: The mean values
 for all parameters were higher in males than females except for the
 maximum intercondylar distance. Sex prediction done with discriminant
 function scores could classify the skull with an overall accuracy of
 70.5%. Conclusions: It can be concluded from the results that the
 morphometric study of the foramen magnum is not suitable for sex
 determination in the Nepalese population.
description: The present study was a descriptive cross-sectional study
 conducted upon the three-dimensional computed tomography (3DCT) images of
 the base of the skull of 261 Nepali individuals whose age and sex were
 known. All the CT images during the study period were from adults who
 presented to the Department of Radiology of Lumbini Medical College
 Teaching Hospital, Palpa for the CT of the head as indicated in the course
 of their management for diagnostic purposes during the period between
 February and September 2021. The study was conducted on
 a normal human skull (more than 20 years of both sexes and matched ages)
 who had a CT scan for various diagnostic medical or surgical indications.
 Only the high-quality reconstructed CT images were included and
 low-quality blurred images or those with artefacts and those which did not
 cover the entire area of the foramen magnum were excluded. Non-contrast CT
 head was done on SIEMENS SOMATOM scope 16 slice CT machine with 0.5 slice
 thickness and studied with OsiriX MD software. Scans of subjects where
 there was gross pathology or injury or any deformity in the skull base
 region were excluded. For the purpose of the study 3DCT
 images were analyzed and various parameters were measured on the console
 of the scanner on a centimetre scale (Figure 1). The measurements less
 than 1 cm were expressed in millimetres which were converted to
 centimetres during data analysis. The parameters that were measured
 were: 
 Foramen magnum length (FML): the distance between the basion and
 opisthion was taken as the antero-posterior length of the foramen magnum
 in the mid-sagittal plane Foramen magnum width (FMW):
 the distance between the lateral margins of the foramen magnum at the
 point of the greatest lateral curvature on either side was taken as the
 transverse diameter of the foramen magnum; perpendicular to the
 mid-sagittal plane Length of right occipital condyle
 (LROC): the distance between the most anterior to the most posterior point
 on the margin of the right occipital condyle along the long
 axis Length of left occipital condyle (LLOC): the
 distance between the most anterior to the most posterior point on the
 margin of the left occipital condyle along the long axis
 Width of right occipital condyle (WROC): the distance between
 the most lateral to the most medial point on the margin of the right
 occipital condyle perpendicular to the long axis
 Width of Left occipital condyle (WLOC): the distance between the
 most lateral to the most medial point on the margin of the left occipital
 condyle perpendicular to the long axis Minimum
 intercondylar distance (MnICD): the distance from the most medial point on
 the margin of the right and left occipital condyles
 Maximum intercondylar distance (MxICD): the distance from the
 most lateral point on the margin of the right and left occipital
 condyles Two radiologists from the
 Department of Radiology obtained the data independently. The observers
 were allowed to manipulate the contrast and brightness features and to use
 the zoom tool of the software for optimal visualization.
 The intra- and interobserver reliability were assessed by
 intraclass correlation coefficient (ICC). The measurements of FM and
 occipital condyles of nearly 10% sample (twenty-five scans) were taken
 twice by one observer with a time interval of 15 days and once by a second
 observer. The recalculated measurements were tested, and the ICC values
 were compared.
description: The measurements thus obtained were then noted into a proforma
 and then entered into IBM SPSS Statistics software v 25 and analyzed. The
 normal distribution of the data was determined by normality plots. The
 continuous variables were presented as mean ± standard deviation (SD).
 Male-female differences were tested using an independent t-test and the
 significance level of the test was defined at p&lt;0.05. Pearson test
 was applied to examine the correlation between the measured foramen magnum
 dimension in both sexes. The foramen magnum dimensions were further
 analyzed using discriminate function analysis using a step-wise method for
 sex predictability.