Mastoid and Opisthion-Bimastoid Triangles for Sex Determination in a Brazilian Sample

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Silvana Regina Prado Penteado de Castro; Juliana Haddad; Alexandre Rodrigues Freire; Olavo Barbosa de Oliveira Neto; Felippe Bevilacqua Prado; Ana Cláudia Rossi & Fausto Bérzin


Human identification involving mutilation, advanced decomposition, and skeletonized materials is a challenge for professionals in forensic medicine and dentistry. This study was aimed at a morphometric analysis of the mastoid and bimastoid triangles to determine sex in a Brazilian population. The sample included 80 human skulls (34 females and 46 males; age: 18 to 60 years) from individuals with death certificates. Linear measurements (mm) of the mastoid process — right (n=3) and left (n=3) — and the opisthion- bimastoid (n=3) triangles were taken (digital caliper) by two previously trained researchers. Three cranial points — asterion, porion and process — were determined for the right and left mastoid triangle and three others — (1) opisthion and (2) right and (3) left mastoid — for the bimastoid triangle. Heron’s formula was used to calculate the area of the triangles assessed. Data were submitted to the Shapiro- Wilk normality test, followed by the unpaired Student's t test or the Mann-Whitney U test, depending on the data distribution verified in the normality test (GraphPad Prism 5.01; p<0.05). The ROC curve was used to measure the accuracy of the variables toward sex determination. The opisthion-bimastoid triangle showed high accuracy and significant differences in all the variables assessed and thus was considered a potential element for sex determination in the Brazilian population assessed.

KEYWORDS: Sex differences; Skull; Craniometry; Mastoid process.

How to cite this article

DE CASTRO, S. R. P. P.; HADDAD, J.; FREIRE, A. R.; NETO, O. B. O.; PRADO, F. B.; ROSSI, A. C. & BÉRZIN, F. Mastoid and opisthion-bimastoid triangles for sex determination in a Brazilian sample. Int. J. Morphol., 39(4):1068-1073, 2021.