European Journal of Cardiovascular Medicine

Even in this modern era of advanced knowledge in medical science, still the human skeleton holds its medicolegal importance in forensic anthropology as before. The forensic pathologists still face the dilemma to identify and opine whether the skeletal remains are of human or not along with estimation of the relatively correct age, sex, and height of the specimen available. Determining the skeletal sex with precise accuracy almost solely depends on methods applied over available materials. [1-3]

Innumerable scientific literature is not unavailable in forensic anthropometry for the identification of human skeletons. The examination of the human skeleton is an integral part to serve medico-legal purpose. The pivotal step of forensic investigation usually starts with the sexual differentiation of the adult human bone. The whole skeleton helps to identify the sex of bone (male/ female) with almost 100% accuracy. But, when only the pelvis or the skull is available, the accuracy get reduced to 90%. If no skull and pelvis are available, it almost a mammoth task to determine the age and sex accurately [4].

In 1881,  Dwight did examination on 30 male and 26 female sterna in the Harvard Medical School. He recorded manubrium length, mesosternum length, and total length. The average manubrium length was found  51.8 mm for males and 46.7 mm for females. The average mesosternum length was found 105.8 mm for males and 89.5 mm for females. The average total length was found 157.7 mm for males and 136.2mm for females. The sternal index was found to be accurate for 60% of males, and 46.2% of females^. [5]

Later, the same scientist, Dwight recorded the measurement of  142 male and 86 female sterna from the Harvard Medical School. As together with his preceding study, measurements protected manubrium length, mesosternum length, and total length. In that study, the average manubrium length was recorded as 53.7 mm for males and 49.4 mm for females. The average mesosternum length was recorded as  110.4mm for males and 91.9 mm for females. The average  total length was found 164.1 mm for males and 141.3 mm for females. The sternal index was found to be accurate for 59.2% of males and 60.5% of females. In both studies, Dwight served a conclusion  that the Hyrtl‘s Law was successful when applied to the mean values, but it failed when applied to the individual^.[6]

In 1956 Ashley stated that the female sterna from both the European and East African samples were smaller than the male sterna. He found the largest difference in measurements occurring between the mesosternum lengths of male and female sterna. Ashley (1956) reported averages of the sternal measurements for both the European population and the East African population. The average manubrium length in the European sample was 52.2 mm for males and 47.9 mm for females. The average manubrium length in the East African sample was 45.9 mm in males and 44.2 mm in females. The average mesosternum length in the European sample was 104.7 mm in males and 90.8 mm in females. The average mesosternum length in the East -African sample was 95.5 mm in males and 82.8 mm in females. The average sternebrae  width in the European sample was 26.4 mm in males and 24.5 mm in females. The average sternebrae 1 width in the East African sample was 24 mm in males and 21.5 mm in females. The average sternebrae width in the European sample was 33.7 mm in males and 30.5 mm in females. The average sternebrae  width in the East African sample was 30.9 mm in males and 26.8 mm in females. The average total length in the European sample was found to be 156.9 mm in males and 138.7 mm in the case of females. In the East African sample, the average total length was found to be 142.6 mm in males and 127.1 mm in case of females. The sterna index was calculated and for the European sample, 52.9% of the males and 69.3% of the females conform to Hyrtl’s Law. In the East African sample, 64.7% of the males and 69.2% of the females conform to Hyrtl's Law. Following the studies mentioned above, Ashley found Hyrtl’s Law to be unreliable, due to large amounts of overlap between male and female values. This was also true for the results of the relative width index. These unreliable tests prompted Ashley to create the sectioning points, based on measurements of total length, known as ‘The 149 Rule’ for Europeans, and The 136 Rule’ for East Africans. Two issues were presented in this article. First, the length of the sternum is related to the height of the individual, meaning the sterna of a tall female could be confused with the sterna of a short male, and vice versa. Furthermore, the second concern is how the length and width of the sternum continue to increase throughout life and this could lead to a difference in the sectioning points, sternal index, and relative width index with age^. [7].

In a relatively recent study, Menezes RG et al. stated that the length of the sternum is a liable predictor of stature in adult South Indian females and can be used as a tool for stature estimation when better predictors of stature like the long bones of the limbs are not available when examining skeletal remains. The study was undertaken to estimate stature from the length of the sternum in South Indian females using a linear regression equation. A linear regression equation [Stature = 111.599 + (3.316 × Length of the sternum)] was derived to estimate stature from the length of the sternum. The correlation coefficient was 0.639. The standard error of the estimate was 4.11 cm^. [8]

Torwalt and Hoppa reported that significant differences exist between males and females when comparing mean values, but that a large percentage of the sample fall within the indeterminate range. The average manubrium length is 54.431 mm for males and 48.793 mm for females. The average mesosternum length is 93.551 mm for females while for male it was 109.406 mm. The average total length is 163.837 mm for males and 142.344 mm for females. The sternebra 1 and sternebra     3 widths are averaged collectively to yield an average of 29.826 mm for males and 24.267 mm for females. [9]

Gautam et al. examined the sterna as it relates to both age and sex. For manubrium length, values less than 33 mm were female and values more than 63 mm were male. For mesosternum length, values less than 48 mm were female and values more than 106 mm were male. For total length, values less than 92 mm were female and values more than 161 mm were male. Any       value that was found to be in the overlapping zone of the above-mentioned cut off points was considered indeterminate. There was no significance found in manubrium width, Mesosternum width, and sternal index. Fusion rates of the sterna were determined to be independent of sex of the individual. On the other hand, they also conducted a study on the sternum in India, and found that there were no differences between sexes regarding the fusion rates of the sternal segments. They report that the lower segments fuse by 15 years of age, and the first and second segments fuse to the lower segments by 21 years of age^. [10]

Dahiphale et al. discovered that the average manubrium length was 48.46 mm for males and 43.78 mm for females. The average mesosternum length was 94.43 mm for males and 70.19 mm for females. For the length of the mesosternum, values greater than 88 mm were considered male, and values less than 76 mm were considered female, with values between 76 mm and 88 mm considered indeterminate. The average sternebra 1 width was 27.17 mm for males and 24.44 mm for females. The average sternebra 3 width was 31.95 mm for males and 28.24 mm for females. The average total length of the sternum was 142.2 mm in males and 113.87 mm in females. These averages were used to create the ―129 rule‖, meaning that sterna measuring less than 129 mm are female and sterna measuring more than 129 mm are male. The average sternal index was 52% in males and 63.01% in females. Methods that proved unreliable were manubrium length, sternal index, sternebra 1 width, and sternebra 3 width. The length of the manubrium and the sternal index were found to have over 90% of the sample falling in the overlapping zone of both sexes. Sternebra 1 width and sternebra three width had been located to nearly absolutely fall withinside the overlapping region of each sexes.[11]

McCormick et al. created an algorithm focusing on costal cartilage ossification patterns in conjunction with sternal measurements. The results relevant to this study refer to manubrium length, sterna length, sternebrae 1 width, and sternebrae 3 width. The average manubrium length was 50.3 mm in females and 55.5 mm in males respectively. Manubrium lengths greater than 60 mm were considered male, and manubrium lengths less than 46 mm were considered female, with manubrium lengths in between 46 mm and 60 mm considered indeterminate. The average sternal length (total length) was 161.6 mm in males and 138.3 mm in females. Sectioning points for sternal length were created and values less than 143 mm were females, and values greater than 157 mm were males, with values in between 143 mm and 157 mm considered indeterminate. For the sterna that did not fall in the indeterminate range, correct sex estimation was achieved in 94.3% of the cases. If the sectioning point was changed to 148 mm, the accuracy rate of the entire sample would be 85.2%. Furthermore, results revealed that sternal lengths are significantly shorter in males less than 25 years of age and in females in the 20-21year age group. The authors note, however, that the male sterna have a tendency to be wider at those factors than woman sterna. [12]

Human Sternum from the cadavers in the Kolkata Police Morgue under the Dept of Forensic Medicine and Toxicology, Medical College & Hospital, Kolkata, being brought for medico-legal autopsy examination in the Department (May 2021—April 2022) were included in this current cross-sectional observational study. The sternum was examined after getting the IEC (Ref. No.- No.- MC/KOL/IEC/NON-SPON/972/01/2021) and being screened via inclusion and exclusion criteria.

Study material –Adult Human Sternum

Study sample – 100 adult dead bodies (55 adult males and 45 adult females) had been taken via means of the complete enumeration technique from dead bodies came for medicolegal autopsies to the Kolkata Police morgue, depending on the criteria set up beforehand. 36 sterna got destroyed during the time of processing and cleaning. Finally, 64 sterna were analyzed of which 38 were Male and the rest 26 were female.

Inclusion Criteria –

• Dead subjects with known sex & age.

Age Group---18 years & above. The age of the deceased was acquired from the next to the kin of the deceased and from the inquests. The age of the deceased was rounded off to full figures.

• Sex --Both male &

Exclusion Criteria –

1. Subjects with apparent fracture of the
2. Subjects with apparent pathology of the
3. Subjects with apparent deformities of sternum.
4. Unknown or unclaimed dead bodies where age cannot be

Technique - The sterna had been removed from the cadavers through sectioning the costal cartilages, beside the costochondral junction. Then after processing with chemicals, the measurements were recorded

Measurements had been taken in millimetres, with the assist of Vernier Calliper

• Width of Manubrium (MW): It was the maximum distance in centimeters up to two decimals between the midpoints of facets for the costal cartilages on both side of the bone. (Figure-4)
• Width of Mesosternum (SW): The It was distance between the left and right third sternebra (depressions between the articulation notches for the fourth and fifth costal cartilage)

Table 1:- Distribution of the study population according to age. (n = 64)

From the above table, we can see the greatest number of cases were from the age group of 18-39 years.

Table 2 :- Distribution of the study population according to sex. (n = 64)

Table 3 :- Overall descriptive statistics for the study population for both sexes.

Table no.3 represents the summary of the descriptive statistics as mean, standard deviation, and standard error of the mean for the transverse metric parameters of the sternum bone considering the overall data without categorizing into age groups for both sexes.

The overall mean along with the standard deviation for males were 50.75 ± 5.35 mm, 34.47 ± 3.40 mm. for Manubrial width and Mesosternal width respectively. Whereas, in the case of female subjects these measurements were 46.15 ± 5.54 mm and 28.63 ± 6.09 mm. respectively.

Table.4 :- Statistical discussion of width of Manubrium (MW) for sexual dimorphism

Table.5 :- Independent Samples T test of Width of Manubrium (MW) for Male and Female Comparison

The above table represents the independent “t” test done to compare the mean manubrial width of the sternum between males and females. There were significant differences in the mean manubrial width of the sternum between the male and female groups.

An independent samples t-test was used to compare the mean manubrial width (MW) score of males (n=38) and females (n=26) Deceased. Neither Shapiro-Wilk statistic was significant, indicating that the assumption of normality was not violated. Levene’s test was also non-significant; thus, an equal variance can be assumed for both groups. The t-test was statistically significant, with mean MW score of males (M=50.75, SD=5.34) was significantly higher (mean difference 4.60, 95% CI [1.83, 7.39]), than the females (M= 46.15, SD=5.54), t (64) =3.32, p<.001, two-tailed, Hedges’s gs = 0.836555. The common language (CL) effect size indicates that the chance that for a randomly selected pair of individuals the MW score of a male is higher than the score of a female is 80%.

Table 6. :- Mean difference of Length of Manubrium (MW) scores between male and female students

Table.7 :- Statistical discussion of Width of Mesosternum (SW) for sexual dimorphism.

Table 8. :- Independent Samples T test of Width of Mesosternum (SW) for Male and Female Comparison

An independent samples t-test was used to compare the mean mesosternal width (SW) score of males (n=38) and females (n=26) Deceased. Neither Shapiro-Wilk statistic was significant, indicating that the assumption of normality was not violated. Levene’s test was also non-significant; thus, an equal variance can be assumed for both groups. The t-test was statistically significant, with mean SW score of males (M=34.47, SD=3.40) was significantly higher (mean difference 5.81, 95% CI [3.17, 8.51]), than the females (M= 28.63, SD=6.09), t (64) =4.43, p<.001, two-tailed, Hedges’s gs = 1.233. The common language (CL) effect size indicates that the chance that for a randomly selected pair of individuals the SW score of a male is higher than the score of a female is 80%.

Table 9.:- Mean difference of Width of Mesosternum (SW) scores between male and female students

For the present study a total of 64 cases have been selected according to the specified sample design; during the period May 2021 to june2022 depending upon the inclusion and exclusion criteria.

The study population comprises of both male and female, from 18yrs to old age. For the sake of analysis and description, the study population has been divided into three age groups; 18years to 39years (group-1), 40years to 59years (group-2), 60years to 90years (group-3). Maximum number of cases i.e., 28(43.8%) are found in the age group of 18 to 39years; followed by 22(34.4%) in the age group of 40 to 59years and 14(21.9%) in the age group of 60 to 90years. [Table-1]

Regarding the sex composition of the study population, male dominance was prevalent as among 64 cases, there were 38 male subjects (59.4%) and 26 female subjects (40.6%). The male: Female ratio in the present study population was 1.46:1. [Table-2]

In the present study, we analysed sexual dimorphism of the Sternum in adults more than 18 years with morphometric analysis of two parameters namely Width of Manubrium and Width of Mesosternum. The final analysis was done keeping in mind the following points-

• Whether the Sternum bone is sexually dimorphic or not.

From Table no.3 it is apparent that for the two transverse linear parameters- Width of Manubrium, and Width of Mesosternum., the measurement is greater in male. It is evident enough the overall mean and standard deviations and the age-group-wise statistics.

From Table no.5 and 8,the Independent ‘t test’ results show that there is a statistically significant (<0.001) difference between mean measurements of male and female samples for each of the four parameters.

The esteemed Professor Bernard Knight articulated that the determination of sex serves as the most significant statistical criterion, as it effectively eliminates nearly half of the population from consideration, in contrast to age, stature, and race, which each encompass a broader spectrum of variables. The present investigation demonstrated that the established linear transverse linear parameters of the sternum serves as a nearly precise indicator of sex. By employing sternum metrics, one can estimate an individual's sex with corresponding accuracy rates. This metric-based approach offers an objective assessment of sex, distinguishing it from the subjective nature of visual evaluations. Furthermore, the use of metrics enables less experienced practitioners to engage with this research and deliver accurate sex estimations without the necessity of extensive experience or familiarity with visual assessment techniques. This study endeavours to facilitate a shift from a morphological to a morphometrical perspective.

Funding

This research received no specific grant from any funding agency in the public, commercial or not-for-profit sectors.

Acknowledgment

We are sincerely thankful and grateful from core of our heart to Prof (Dr.) Biswajit Sukul, Professor and Head of the Department, FMT of Gouri Devi Medical College to act as the orchestra master of our study

Conflict Of Interest

The authors declare that there is no conflict of interest. This research work is a part of the dissertation of the First Author, submitted at the West Bengal University of health sciences in compliance with partial fulfilment of eligibility for the MD Examination for the year 2022.

1. Osunwoke EA, Gwunireama IU, Orish CN, et al. A study of sexual dimorphism of the human sternum in the south Nigerian population. Journal of Applied Biosciences.2010;26: 1636-9.
2. Jit I, Bakshi V. Time of fusion of the human mesosternum with manubrium and xiphoid process. Indian Journal of Medical Research.1986;83:322-31.
3. Ashley GT. The human sternum- The influence of sex & age on its measurements. Journal of Forensic Medicine.1956;3:27-43.
4. Gautam RS, Shah GV, Jadav HR, Gohil, B.J. The Human Sternum – as An Index of Age & Sex. Anat. Soc. India 2003;52(1):20-3.
5. Dwight T. The Sternum as an index of sex and age. I. Journal of Anatomy.1881;15:327-30
6. Dwight T. The Sternum as an index of sex, height and age. I. Journal of Anatomy. 1890;24: 527-35.
7. Ashley GT. The human sternum- The relationship between the pattern of ossification and the definitive shape of the mesosternum in man. J Anat.1956;90(1):87-105.
8. Meneges RG, Kanchan T, Kumar GP, et al. Stature estimation from the length of the sternum in South Indian males: a preliminary study. Journal of Forensic Legal Medicine. 2009;16(8):441-3.
9. Torwalt CRMM, Hoppa RD. A Test of Sex Determination from Measurements of Chest Radiographs. Journal of Forensic Sciences.2005;50(4):1-8
10. Gautam RS, Shah GV, Jadav HR, Gohil BJ. The Human Sternum- as An Index of Age & Sex. Journal of the Anatomical Society of India.2003;52(1):20-3
11. Dahiphale VP, Baheete BH, Kamkhedkar SG. Sexing The human Sternum in Marathwada Region. Journal of Anatomical Society of India.2002;51(2):162-7
12. McCormick WF, Steward JH, Langford LA. Sex Determination from Chest Plate Roentgenograms. American Journal of Physical Anthropology.1985;68:173-95