## Sexing The Human Sternum In Marathwada Region

#### Author(s): Dahiphale V.P., Baheete B.H., Kamkhedkar S.G.

#### Vol. 51, No. 2 (2002-07 - 2002-12)

Department of Anatomy, S.R.T.R. Medical College, Ambajogai. Maharashtra, INDIA

### Abstract

For differentiating a male from a female sternum, a metrical study of 143 adult human sterna consisting of 96 male and 47 female was done. These sterna were obtained from - S.R.T.R. Medical College, Ambajogai & Govt, Medical College, Aurangabad.

If the length of mesosternum was more than 88 mm, the sternum was male and if less than 76mm, it was female. While no opinion could be given if the length was between 76-88 mm; by its measurement 69.80% male and 76.60% female sterna could be sexed.

The combined length of manubrium and mesosternum could also determine the sex correctly in 38.54% male and 57.45% female specimens. The other parameters like the length of manubrium, manubrium- corpus index, width of 1st and 3rd sternebrae were not found to be so useful in sexing a given sternum.

By applying multivariate analysis the probability of correctly identifying the sex of sternum was increased upto to 89%.

**Key words:** Human Sternum, Marathwada region, metrical study, sexing

### Introduction:

A difference in the ratio between the length of the manubrium and that of mesosternum in the two sexes was first described by Wenzel (1788). His findings were supported by Hyrtl (1853), and Dwight (1890). According to the Hyrtl's law the ratio between the length of the manubrium and that of the mesosternum is more than 1:2 in the case of women, and less in men. Paterson (1904) recorded that the mesosternum was longer and narrower in the males than in females.

For sexing the European sterna Ashley (1956) formulated the " rule," according to which a male sternum exceeded 149 mm in length, where as the female sternum was less than 149 mm. To sex the North Indian sterna Jit et al (1980) showed that the said rule was not applicable to Indian sterna, which were shorter in length.

The present work is an attempt to sex the sterna in Marathwada region of Maharashtra on the basis of metrical study.

### Material and Methods:

Material for the present study consisted of 143 sterna (96 male and 47 female) obtained from medical colleges at Ambajogai and Aurangabad. Random sampling of fully ossified and normal sterna was done and measured with the help of vernier caliper. Measurements were taken in millimeters, according to technique described by Jit et al (1980).

**1. Length of manubrium (M):** It is the distance
from suprasternal notch to manubriomesosternal
junction in midline. (X_{1})

**2. Length of mesosternum (B) :** It is the
distance from manubriomesosternal junction to
the mesosterno-xiphoidal junction in the
midline. (X_{2})

**3. Combined length of manubrium and mesosternum= M + B (X _{3}) **

**4. Breadth of first sternebra at its waist = S _{1} (X_{4}) **

**5. Breadth of third sternebra at its waist = S _{3} (X_{5})**

From above measurements following indices were obtained.

**6. Manubrio-corpus index = M/B ×100 (X _{6}) **

**7. Relative width index of first and third sternebrae = S _{1}/S_{3} ×100 (X_{7}) **

The data obtained was analysed statistically to find out the mean and standard deviation. The 'z'- test was applied to find out wheather the sexual differences between means were significant or not. The bar diagram of each parameter was plotted taking measurements on X axis and number of cases on Y axis. From the bar diagram the overlapping zone, identification point and percentage of cases beyond the identification point were determined for each parameter.

#### In the bar diagram.

- Violet Colour indicates male cases
- Sky blue colour indicates female cases
- Faint brown colour indicates overlapping zone

To increase the accuracy in sexual determination, discriminant functions were generated on the basis of five variables (quantitative traits) mentioned above.

### Observations:

The results of various measurements and indices are shown in Table No. 1. It shows that the level
of significance of the difference between the means of each of five parameters, & manubrium corpus
index is statistically highly significant (P<0.001). But
the incidence of overlapping is greater than 93%
with regard of M, S_{1}/S_{3}and sternal index. Only the length of mesosternum and M+B are the measurements seen to be valuable in determining the sex.
The level of significance between the means of the
relative width indices (S_{1}/S_{3} X 100) of two sexes is insignificant (P>0.05), as bar diagram also proved
that the indices overlap in 99% cases.

**Length of mesosternum:** In 67 (69.80%)
male sterna, the length of mesosternum was more
than 88 mm which was the maximum length recorded in the female specimens. While in case of 36
(76.60%) female sterna, it was less than 76 mm
which was the smallest length in a male sternum,
these results are illustrated in Fig-1.

#### Table I. Various measurements of the sterna in the two sexes. Number of observations Male-96, Female-47

Parameters | Sex | Range | Mean | S.D. | Level of Significance for the difference between the means |
No. and (%) of Cases falling within the Overlapping Zone |
---|---|---|---|---|---|---|

Length of Manubrium (M) | M | 35-65 | 48.458 | 5.586 | P < 0.001 | 91 (94.79) |

F | 33-56 | 43.781 | 5.238 | 45 (93.61) | ||

Length of Mesosternum (B) | M | 77-120 | 94.427 | 9.521 | P < 0.001 | 29 (30.20) |

F | 51-88 | 70.191 | 8.541 | 11 (23.40) | ||

Combined length (M+B) | M | 114-170 | 142.196 | 11.297 | P < 0.001 | 59 (61.45) |

F | 91-144 | 113.872 | 12.024 | 20 (42.55) | ||

Width of 1st Sternebra (S_{1}) |
M | 20-38 | 27.166 | 3.885 | P < 0.001 | 95 (98.95) |

F | 18-36 | 24.444 | 4.129 | 42 (89.36) | ||

Width of 3rd Sternebra (S_{3}) |
M | 20-56 | 31.947 | 5.77 | P < 0.01 | 85 (88.54) |

F | 18-38 | 28.236 | 4.719 | 43 (91.48) | ||

Manubrium-Corpus Index (M/B × 100) | M | 36-77 | 51.995 | 8.34 | P < 0.001 | 4 (44.79) |

F | 51-91 | 63.01 | 8.507 | 2 (95.74) | ||

Relative Width Index (S_{1}/S_{3} X 100) |
M | 63-123 | 86.291 | 12.678 | P > 0.05 | 93 (95.74) |

F | 68-114 | 87.16 | 12.423 | 43 (100) |

**Combined length of manubrium and
mesosternum: **It was more than 144 mm in
27(38.54%) male specimens which was the maximum length in female specimens, While in
27(57.45%) female specimens it was less than 114
mm, which was the minimum length in male sterna
(Fig. 2).

### Discriminant Functions

A multivariate linear discriminant analysis technique (Armitage 1971) was applied to the data, and discriminant functions were generated.

The linear function is given by
Z=b_{0}+x_{1}b_{1}+x_{2}b_{2}+x_{3} b_{3}+x_{4} b_{4} + x_{5} b_{5} + x_{6} b_{6} + x_{7} b_{7}

(1)

Where, x_{1} to x_{7} are the variables mentioned earlier,
b_{0} = Constant, b_{1} to b_{7} - are the coefficients

The values of b_{0}, b_{1} to b_{7} were obtained by using standard computer programe. On substituting
values of b_{0}, b_{1} to b_{7} in equation 1, we get.

Z = -10.996 + (0.046) x_{1} + (0.064) x_{2} + (0.013) x_{3} + (-0.01) x_{4} + (0.073) x_{5} + (-0.038) x_{6} + (0.02) x_{7}

(2)

By substituting average values corresponding
to males and females in the discriminant function.
The mean value of Z_{M} and Z_{F} are obtained for
male and female group respectively. The respective
functions for Z_{M} and Z_{F} are as follows,

and

X_{M1} to X_{M7} are the average values of the variables

corresponding to male and x_{f1} to X_{F7} corresponding to female. On substituting average values in
equation 3 and 4 we get

Further, for allocating an individual specimen to one of the two groups the end point Z is obtained as follows.

If Z_{M} ×Z_{F} the allocation rule is: Allocate an
individual specimen to the male group if Z>Z_{0} and

to the female group if Z<Z_{0}.

In the present study the value of Z for each specimen is calculated by substituting the values of the variables in the linear function (equation No. 1). The sternum is allocated to the male category when the value of Z was more than - 0.441237 and to the female group if less than - 0.441237. By using this rule 92% male and 87% female sterna can be sexed correctly.

### Discussion:

The observations of various workers regarding the sexual differences in the length of manubrium, mesosternum and combined length of manubrium and mesosternum are given in the table no II.

#### Length of Manubrium

The present observations indicate that although the difference between the average length of male and female manubria is 4.7 mm which is statistically highly significant (p<0.001), this parameter is not so helpful for sexing the individual specimens, because in this study 94% cases lie in overlapping zone. This is in accordance with Ashley (1956) and Jit et al (1980). Dwight (1890) found that the variations in the length of manubrium in two sexes is very small.

#### Length of mesosternum

In the present study the average difference in the length of mesosternum is 24.24 mm which is statistically highly significant (p<0.001). Here it is found that the length of mesosternum is extremely useful in determining the sex of sterna in Marathwada region of Maharasthra, because the length of mesosternum is twice or more the length of manubrium in male and less than twice in female.

#### Table 2: Sexual Differences recorded by various workers in the lengths of the manubriua, mesosterna and combined lengths of manubriua and mesosterna

Manubrium (M) | Mesosternum (B) | Manubrium + Mesosternum (M + B) | |||||||
---|---|---|---|---|---|---|---|---|---|

Sr. No. | Name of Workers | sex | No of Specimens | Mean Length | Diff in mean | Mean Length | Diff in mean | Mean Length | Diff in mean |

1 | Dwight (1881) | M | 30 | 51.8 | 5.1 | 105.9 | 16.5 | - | - |

F | 26 | 46.7 | 89.4 | - | |||||

2 | Strauch (1881) | M | 200 | - | - | 110 | 20 | - | - |

F | - | - | 90 | - | |||||

3 | Dwight (1890) | M | 142 | 53.7 | 4.3 | 110.4 | 18.5 | 164.1 | 22.8 |

F | 86 | 49.4 | 91.9 | 141.3 | |||||

4 | Paterson (1904) | M | 310 | 52 | 4.7 | 103.7 | 12.7 | - | - |

F | 126 | 47.3 | 91 | - | |||||

5 | Ashley (1956) African | M | 85 | 45.9 | 1.7 | 96.5 | 13.6 | 142.6 | 15.5 |

F | 13 | 44.2 | 82.9 | 127.1 | |||||

6 | European | M | 378 | 52.2 | 4.3 | 104.7 | 13.9 | 156.9 | 18.2 |

F | 168 | 47.9 | 90.8 | 138.7 | |||||

7 | Jit et al, (1980) | M | 312 | 51.73 | 3.31 | 95.35 | 16.75 | 147.08 | 20.06 |

F | 88 | 48.42 | 78.6 | 127.02 | |||||

Present Study (2000) | M | 96 | 48.458 | 4.677 | 94.427 | 24.236 | 142.196 | 29.324 | |

F | 47 | 43.781 | 70.191 | 113.872 |

Fig. 1 indicates the co-extensive range which lies between 76 to 88 mm, so 30.20% male and 23.40% female sterna fall within the range of other sex. These findings are co-related with Ashley (1956) and Jit et al (1980.)

### Manubrio - Corpus index (Sternal Index)

According to Wenzel (1788) the manubrium in the two sexes, is almost equal in length, but the mesosternum is proportionally longer in males than the females. This led to enunciation of Hyrtl's law, according to which manubrio corpus index (sternal index) exceeds 50 in females and is less than 50 in males. Table No. III gives the percentage of cases obeying the law in the two sexes.

In the present study 100% female and 52.20% male specimens obey the law. However, the manbrium - corpus indices of one sex fall within the range of other sex n 95% cases. Therefore, the law when applied to an individual specimen is not helpful in determining the sex. This is in agreement with Ashley (1956) and Jit et al (1980) who found the law to be 'unreliable.'

### Combined Length of the manubrium and mesosternum.

Ashley (1956) recorded the average combined length (M+B) in European sterna to be 156.9 mm in males and 138.7 mm in females, giving an absolute difference of 18.2 mm. By "Trial and error", he concluded that a combined length of 149 mm was the dividing line between the two sexes. According to him 'The 149 rule', was applicable to 76.7% male and 80.4% female European sterna. Similarly for East Africans he derived "the 136 rule", which was applicable to 77.6% male and 84.6% female sterna.

#### Table 3: Ablitty of Hyrti's Law (M/B × 100=<50 Males >50 Female) as recorded by various workers

Observer | Year | Number of Specimens |
Sex | % Obeying Law |
---|---|---|---|---|

Dwight | 1890 | 142 | M | 59.10 |

86 | F | 60.40 | ||

Patermoller | 1890 | 55 | M | 65.00 |

33 | F | - | ||

Krause | 1897 | - | M | - |

14 | F | 43 | ||

Ashley (African) | 1956 | 85 | M | 64.70 |

13 | F | 69.20 | ||

European | 1956 | 378 | M | 52.90 |

171 | F | 69.30 | ||

Narayan and Varma | 1958 | 126 | M | 34.12 |

27 | F | 81.48 | ||

Jit, et al | 1980 | 312 | M | 31.08 |

88 | F | 88.64 | ||

Present study | 2000 | 96 | M | 52.20 |

47 | F | 100 |

However, he shows that the cut off point can be arrived by halving the co-extensive range of the combined lengths in the two sexes. He shows that coextensive range of the two sexes in European sterna extends from 126 mm to 171 mm, and therefore any sternum of unknown sex having a combined length (M+B) within this range can not be sexed with certainty. The co-extensive range covered 341 out of 378 male (90.2%) and 153 out of 160 female (91.1%) sterna.

Jit et al (1980) found that the combined length is extremely useful in determining the sex of North Indian sterna. The average difference between the means is 20.06 mm which is statistically highly significant (P<0.001). They also applied "the 136 rule", given by Ashley (1956). By which they determined the sex of 86% male and 78% female sterna, but individually they cant's say if any particular sternum given is definitely male or female.

In the present study the difference between the average combined length is 29.324 mm which is statistically highly significant. The co-extensive range is 114-144 mm and by halving the same, we can come to "The 129 rule", similar to that given by Ashley (1956). By applying this rule 91.66% male and 82.97% female sterna can be identified correctly. In this study 61.46% male and 42.55% female sterna fall within the range of overlapping zone (Fig. 2.).

### Width of 1st and 3rd Sternebrae

In the present study also the measurement of sternbrae 1 and 3 in both sexes fall in overlapping zone almost completely. So in the present study these parameters were not found to be helpful in determination of sex. Similar findings were recorded by Jit et al (1980).

Relative width index of sternebrae 1st and 3rd
Ashley (1956) described an index S_{1} /S_{3} X 100.

He showed that the range of values in males and females overlapping were practically co-extensive. He, therefore did not give any further consideration to this difference.

Jit et al (1980) also concluded the same as that of Ashley (1956). In the present study as shown in Table-I the difference between the means of indices was statistically insignificant (P>0.05). Therefore, this index is not useful for sexing the sternum.

### Multivariate Analysis

In the present study we subjected our data to multivariate discriminant analysis technique as given by Armitage (1971) and by this method 92% male and 87% female sterna can be sexed correctly.

Penrose (1947) and Jit et al (1980) also applied multivariate analysis and they found that 89% male and 82% female sterna could be sexed correctly.

### Conclusion:

1. Out of all the parameters, the length of mesosternum (B) distinguishes 69.80% male and 76.60% female sterna and with the combined length of manubrium and mesosternum (M+B) 38.54% male and 57.45% female sterna can be sexed correctly.

2. By applying the multivariate linear discriminant analysis technique 92% male and 87% female sterna can be sexed correctly.

### References:

- Armitage, P. : Statistical methods in medical research, Blackwell Scientific Publications, Oxford and Edinburgh : pp. 332-335. (1971)
- Ashley G.T. (1956) : Typing of the human sternum. The influence of sex and age on its measurements. Journal of Forensic Medicine, 3: 27-43.
- Dwight, T. (1890) : The sternum is an index of sex, height and age, Journal of Anatomy, 24: 527-535.
- Hyrtl, J. (1893) : handbuch der Topographischen Anatomic percentage Bd. 1, S. 348.
- Jit, I., Jhingan, V. and Kulkarni, M. (1980) : Sexing the human sternum. American Journal of Physical Anthropology, 53: 217-224.
- Krause, W. (1897) : Ueber das weibliche sternum. Int. mschr. Anat. Physiol; Bd. 14, S. 21-26.
- Narayan, D. and Varma, H.C. (1958) : Sternal index for male and female in U.P. Journal of Anatomical Society of India 7: 71-72.
- Patermoller, F. (1890) : Uberden Sogen, Geschlechstypus des menschichen Brustbeings. Diss med. Kiel.
- Paterson, A.M. : The Human sternum. Williams and Norgate, London: University Press of Liverpool pp 36-37 and 77. (1904)
- Penrose, L.S. (1947) : Some notes on discrimination. Annales of Eugenics, 13: 228-237.
- Pons, J. (1955) : The sexual diagnosis of isolated bones of the skeleton. Human Biology, 27: 12-21.
- Strauch, M. (1881) : Anatom. Untersuch ungen uber des Brustbeing des menschen Dissertat. Dorpat.
- Wenzel, J. (1788) : Quoted by Ashley. 1956.

#### Fig. 1: Length of Mesosternum

Number of specimens are ploted against the length of the mesosternum in the two sexes. Measurements between 76 and 88mm in one sex fall within the range of other sex.

#### Fig-2 : Combined Length of the Manubrium and Mesosternum.

Number of specimens are ploted against the combined length of the manubrium and mesosternum in the two sexes. Measurements between 114 and 144 mm in one sex fall within the range of the other sex.