Gender Determination Using Sacral Anthropometry – Systematic Review

ABSTRACT

Background:  The sex determination parameters in humans plays a vital role in the antemortem analysis.

Aim: To aim of this systematic review is to analyze the differences and similarities in the anthropometrical values of various sacral parameters in males and females.  And to find out the best criteria for studying sexual dimorphism of the sacrum.

Materials & Methods: This study included 140 human sacral bones from the Anatomy Department, Quaid-e-Azam Medical College, Bahawalpur, Punjab – 83 male and 57 female known bones. The measurements that were taken, tabulated, and analyzed statistically were sacral index, ventral straight length and breadth of sacrum, index of the body of the first sacral vertebra, and anteroposterior and transverse diameter of the sacrum.

Results: The mean values for the sacral index were 98.44±4.69 mm in male and 113.23±5.61 mm in the female. The average measurement for straight ventral length was 104.7±5.94 mm in male and 92.6±6.1 mm in female, and maximum breadth was 102.93±4.83 mm in male and 104.77±6.48 mm in the female. The average transverse diameter values of the first sacral vertebra were 48.48±4.21 mm in male and 40.75±3.51 mm in female, and anteroposterior diameter was 29.12±2.47 mm in male and 26.93±2 mm in the female. And the index of the body of the first sacral vertebra was 60.28±4.96 mm in male and 66.36±5.04 mm in the female.

Conclusion: The systematic review demonstrated that the sacral index was the most accurate and optimal indicator for sex determination sacrum. Though no single parameter can is good enough for identifying 100% of the bones – but sacral index alone was able to identify 56.8% of bones in females and 26.61% of bones in males.

Keywords: Sacrum, Sacral anthropometry, Sacral index

 

INTRODUCTION

Gender determination is the most vital part in establishing the biological profile in human osteology. Sex determination is essential for making age, race, and height estimations. Anthropologists regard sacrum as an integral component in the gender determination process of a deceased individual.

The sacrum is the main supporting bone of the pelvic cavity that forms its posterosuperior walls of it. It is a triangular bone which is formed by the fusion of five sacral vertebrae. It marks the caudal end of the vertebral column.

‘Sacral index’ is long acknowledged by anatomists as the most significant metrical parameter to differentiate between male and female sacral bones. The following formula calculates it; Sacral Index = (sacral breadth/sacral length) X 100

The focus of this systematic review is on identifying the best metrical parameter for establishing and defining the gender, based on studying sexual dimorphism of the sacrum.

 

MATERIAL AND METHODS

The present systematic review relies on a total of 140 human sacral bones, of which 57 are female, and 83 are male adult sacral bones. The bones used in this review were parched, fully ossified, and deformity-free. The data used in this systematic study is from the Anatomy Department of Quaid-e-Azam Medical College, Bahawalpur, Punjab. The values recorded were taken via vernier calipers, steel measuring scale, and a pair of dividers. The observed parameters and protocols are as follows:

  1. Ventral Straight Length: From the midpoint of the anterosuperior border of sacral promontory, along the midsagittal plane, to the mid of anteroinferior border of the last sacral vertebra
  2. Sacral Breadth: From the midpoint of the left and right alae of the sacrum.
  3. Sacral Index: By using formula: (sacral breadth/sacral length) X 100
  4. 1st Sacral Body Transverse Diameter: noted by Vernier calipers
  5. 1st Sacral Body Anteroposterior Diameter: noted Vernier calipers
  6. 1st Sacral Vertebra Index: Calculated by using the following formula: (A-P Diameter of S1 body/transverse diameter of S1) x 100

The demarking point (D.P.) of a certain metrical value for identifying male sacrum was more than 3 S.D. of the mean value for females. And for female sacrum identification, the D.P. for the same values were less than 3 S.D. of the mean value of the male sacrum. The study data is present in a tabular form, and calculation of various statistical markers is as below:

 

Table 1: Results for straight ventral length, maximum breadth, and sacral index. [H.S. = highly significant, N.S. + not significant] all values in mm.

Parameters Ventral straight length Maximum breadth Sacral index
Male Female Male Female Male Female
No.# of bones 83 57 83 57 83 57
Range 90.35-122.39 81-110.64 92.65-115.65 88.98-126.54 86.78-116.09 99.13-123.11
Mean 104.73 92.64 102.93 104.77 98.44 113.23
S.D. 5.94 6.10 4.83 6.48 4.69 5.61
Mean ± 3 S.D. 86.91-122.55 74.34-110.94 88.44-117.42 85.33-124.21 84.37-112.51 96.4-130.06
Demarking point >110.94 <86.91 >124.21 <88.44 <96.4 >112.51
% of bones identified 16.86 19.30 0 0 27.71 57.9
t value 11.71 1.923 16.93
p value <0.0001 (H.S.) <0.0566 (N.S.) <0.0001 (H.S.)

 

Table 2: Results for maximum transverse diameter, anteroposterior diameter, and 1st sacral body vertebra index. [H.S. = highly significant, N.S. + not significant] all values in mm.

Parameters Maximum transverse diameter Anteroposterior diameter 1st sacral body vertebra index
Male Female Male Female Male Female
No.# of bones 83 57 83 57 83 57
Range 40-62.1 34-48.02 22.26-37.42 23.09-30.73 48.47-72.02 56.08-77.52
Mean 48.48 40.75 29.12 26.93 60.28 66.36
S.D. 4.21 3.51 2.47 2.00 4.96 5.04
Mean ± 3 S.D. 35.85-61.11 30.22-51.282 21.71-36-53 20.93-32-93 25.4-75.16 51.24-81.48
Demarking point >51.28 <35.85 >32.93 <21.71 <51.24 >45.4
% of bones identified 18.07 10.53 2.40 0 1.43 0.71
t value 11.39 5.577 7.085
p value <0.0001 (H.S.) <0.0001 (H.S.) <0.0001 (H.S.)

 

DISCUSSION

In this systematic review of a gender determination study based on sacral anthropometry, values of the sacral index, width sacrum, first sacral vertebra index were significantly higher in female sacral bones. In contrast, parameters like length of sacrum and diameters of first sacral bone were more elevated in male sacral bones. The sacral index means value for male bones was 98.44, and for females, it was 113.23. The D.P. in males was less than 96.4, while in females, it was higher than 112.51. By using the sacral index, 57.9% of sacral bones in females, and 27.71% of bones in males were accurately identified. This parameter offers a high level of significance (P<0.0001).

Though some other studies in the past showed slight variations in the sacral indexes of both sexes, sacral indexes remained a significant parameter. It is still the best parameter amongst other metrical measurements. All other parameters demonstrated a low level of significance when compared to the sacral index. It is best to incorporate the sacral index with other different metrics to help increase the accuracy and efficiency of gender determination.

CONCLUSION

In this systematic review highlighted the accuracy and effectiveness of sacral index in gender identification of sacrum. 57.9% of the female bones and 27.71% of the male bones were accurately identified by using the sacral index alone. All the other parameters, including breadth of sacrum, length of sacrum, transverse diameter, first sacral body index, were of very low significance for gender identification. However, no single parameter could demonstrate 100% sex determination in human sacral bones. So, we can safely imply that a combination of all sacral parameters is to be used to attain the best possible results with 100% accuracy.

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