MULTI-SLICE COMPUTED TOMOGRAPHY OF THE SEVENTH CERVICAL AND FIRST THORACIC VERTEBRAE AS A NEW TOOL FOR SEX IDENTIFICATION AMONG EGYPTIANS

Background: The Biological profile (which includes sex, age, race, and stature) of human remains has an important role in forensic medicine and physical anthropology; sex is the most and first important parameter. Vertebrae exhibit morphological characteristics that make them easily identifiable if recovered from a scene. Previous studies proved sexual dimorphism of the seventh cervical and the first thoracic vertebrae, however, never investigated among Egyptians. Hence, the aim of this work is to investigate the role of these vertebrae in Sex identification among the Egyptians. Materials and Methods: This study was a cross-sectional analytical study. Seven measurements (Maximum sagittal length (XSL), Length of the vertebral foramen (LVF), Maximum width of the vertebral foramen (WVF), Sagittal maximum body diameter (SBD), Maximum transverse diameter of the body (TBD), Maximum height of anterior vertebral body (XHA), Maximum height of posterior vertebral body (XHP)) were taken from computed tomography scans of the seventh cervical (C7) and first thoracic (T1) vertebrae of 112 Egyptians whom age was from 20 to 60 years with no vertebral or bone diseases. The statistical package for social science (SPSS version 21) was used for data analysis. Results: Males were proved to have statistically significantly larger measurements than females (p > 0.005) for all measurements of C7 and T1, and sex could be determined at an accuracy of 84.4% and 89.3% for C7 and T1 respectively. Conclusion: This study showed a significant difference in measurements of the seventh cervical vertebrae and the first thoracic vertebrae for sex discrimination so this can suggest that these two vertebrae could be added to other sex-identifying tools in crime or death scenes for the Egyptian population .


INTRODUCTION
In forensic medicine and physical anthropology, sex identification is important for completing a biological profile (besides age, race, and stature) of human remains (Torimitsu et al., 2016).Regarding sex identification, big bones like the pelvis and skull are used with high accuracy 95-100 % (Badr El Dine and El Shafei, 2016), though, these bones may be absent or destroyed in a scene (Marlow and Pastor, 2011).Therefore, many previous studies have attempted to determine sex by metric analysis of other bones as femur (Cuzzullin et al., 2022)

Ethical approvals:
The ethical and scientific Committees of forensic medicine and clinical toxicology department as well as that of faculty of medicine, in Cairo University approved this study.

Inclusion criteria:
Age of patient from 20-60 with no history of bone disease.

Exclusion criteria:
Bone diseases as congenital diseases, fracture, osteoarthritis, tumors, surgery or metabolic bone diseases were excluded.

Principle:
The participant body was exposed to direct X-rays through a spinning tube.The orientation of the sensors along the length (zaxis) of the body allows the scanners to acquire 4, 8, 16, 64, or more segments with each spin of the x-ray duct.The gained scans can be remodulated into two-and three-dimensional planes.

Procedure:
The scanning process was conducted to get 1.5 mm sections thickness; bone window and clarity B70 for maximum image vision using the software program analyze (Syngo VB 42).photos that didn't show clear borders were adjusted as maximum intensity projection (MIP) images.

Statistical analysis
The data was analyzed using SPSS (statistical package for social science) version 21.We used Independent T-test for comparing qualitative data, when variables were proved to have significant association (p < 0.05) with sex we then tested it in stepwise discriminant function analysis.In this study: twenty randomly selected cases of each sample were repeated one weak apart by the same forensic pathologist to evaluate intra-observer errors.Another randomly selected twenty cases were repeated by the consultant radiologist to evaluate inter-observer errors.

Table (2)
shows relative technical error of measurement (rTEMs) and the coefficient of reliability (R) values for the consideration of intra-and inter-observer errors; they were <1.5% for rTEMs; R values were >0.75.
Males were proved to have statistically significant larger measurements than females (p > 0.005) for all measurements of C7 and T1 (table 3 &4).For S >0, the individual is assigned as male and as female if otherwise.

Table (4):
The difference between males and females in measurements of the first thoracic vertebrae among a sample of Egyptian population (n=112) (p<0.05*)significant, (p<0.001**)highly significant

DISCUSSION
The current work was able to prove that all measurements taken both from the 7th cervical vertebra and also, the 1st thoracic vertebra exhibited statistical significance between different sexes.Furthermore, the current study revealed that sex could be determined from C7 and T1 at high accuracy 84.4 % and 89.3% respectively.
This proved sexual dimorphism of these vertebrae thought to be explained by greater growth in transverse diameter and growth spurt in height of vertebra in males (Marlow and Pastor, 2011), or may be due to other factors as, genetic, physical activity, socioeconomic status, dietary intake (calories, protein, vitamin D, and calcium), and hormonal levels (Rozendaal, 2016).

Amores et al. (2014) conducted a study in
Spain and, reached to nearly similar results for C7; they showed that males were significantly larger than females.However, they reached that LVF of C7 was the most accurate for sex determination with accuracy rate 65.5% -80.2% (table 5).Also Unluturk and Iscan (2014) by studying a Turkish sample, were able to identify sex from measurements of T1 at accuracy rates ranging from 84% to 89%.
In addition, Kibii et al, (2010), by studying a South African sample proved Sexual dimorphism in vertebral body and foramen dimensions with more accurate body dimensions.2018), in which they considered a sample of African Americans, that foramen dimensions of C7 were significantly different between males and females.However, Rozendaal, (2016) reported that on a study carried out on white European populations, WVF was only significant to differentiate between males and females besides vertebral body heights (XH) while LVF wasn't significant.

Males
The study of Palancar et al., (2021) which was carried out on a sample of Europeans, Africans, and Greenland Inuit, proved that the differences in sagittal diameter of body and foramen of C7 between males and females were statistically significant, despite that they took measurements on lateral radiographs.Also Rohmani et al., (2021) on their study on lateral radiographs of C7 of French sample proved sexual dimorphism in LMA and SBD which is similar to this study.
In addition, Sharma et al., (2017) on their study which was conducted in India, reported significant sexual dimorphism in the vertebral bodies of cervical vertebrae (from third to seventh) with the sagittal diameter more significant than transverse diameter.Hora and Sládek, (2018) also observed that vertebral body diameters were larger in males with accuracy of 95%.
Amores and Viciano, (2022) showed significant sexual dimorphism in a sample collected from Portugal when comparing cervical vertebrae, from the second to the seventh vertebrae with accuracy ranging from 80.0% to 92.5%.
In contrast to the current findings, Ruhli et al, (2006) revealed a slight greater vertebral foramen diameter (LVF) of C7 and T1 in Swiss females than in males.

CONCLUSION&RECOMMENDATIONS
This study showed significant difference in measurements of the 7th cervical and the 1 st thoracic vertebrae for sex discrimination so this can recommend that theses vertebrae can be added to other sex identifying tools in crime or death scene for Egyptian population.

CONFLICTS OF INTEREST STATEMENT AND FUNDING
Seven measurements [Maximum sagittal length (XSL), vertebral foramen length (LVF), Maximum width of the vertebral foramen (WVF), Sagittal maximum body diameter (SBD), Maximum transverse diameter of the body (TBD), the Maximum height of anterior vertebral body (XHA), Maximum height of posterior vertebral body (XHP)] were measured for C7 and T1 as shown in figure 1, table 1(Amores et al., 2014, Albright, 2007).The Calibrated ruler of the system was used for measurements; approximation to the nearest 0.1 millimeter was done.

Figure ( 1 ):
Figure (1): Measurements of the seventh cervical and the first thoracic vertebrae from multi-slice computed tomography of our study.(A) in sagittal plane, (B) in axial plane.Each line takes the same color of its written measurement name abbreviation Maximum sagittal length (XSL), Length of the vertebral foramen (LVF), Maximum width of the vertebral foramen (WVF), Sagittal maximum body diameter (SBD), Maximum transverse diameter of the body (TBD), Maximum height of anterior vertebral body (XHA), Maximum height of posterior vertebral body (XHP) (Amores et al.,2014, Albright, 2007).

Table ( 2):Inter-observer and
intra-observer error rates for the seventh cervical and first thoracic vertebrae.

Maximum width of the vertebral foramen (WVF), and also, Maximum sagittal length (XSL) were the most accurate sex identifying measurements of C7 (table 3), while for T1 Maximum height of posterior vertebral body (XHP), Maximum sagittal length (XSL), and Maximum width of the vertebral foramen (WVF) were the most accurate measurements (table 4) Table (3): Difference
between males and females in measurements of seventh cervical vertebrae among a sample of Egyptian population (n=112)

Table ( 5
); Stepwise discriminant function analysis of measurements of seventh cervical and first thoracic