Validity of Metric Assessment of Mastoid Triangle in Sex Determination: An Anatomical Study

Cranial anatomical structures with high sexual dimorphism in metric and morphological evaluation: A systematic review

The mastoid process has attracted the attention of several researchers due to its protected position at the base of the skull and the fact that it is relatively compact, in addition to being highly resistant and dimorphic, considered as a gold standard anatomical structure in the determination of the sexual dimorphism of skulls. However, intrinsic and extrinsic factors may influence this anatomical structure over time, providing contradictory and ambiguous data. Therefore, other anatomical structures need to be evaluated concurrently with the mastoid process to provide better accuracy and reliability of skull sexual dimorphism data. Thus, the objective of this systematic review was to evaluate the degree of reliability of the mastoid process to determine sexual dimorphism compared to other dimorphic structures, since there are still no systematic reviews on the subject in the literature. This review follows the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) and was recorded in the Prospective International Systematic Reviews Registry (PROSPERO) (CRD 42023395167 Systematic Registry) (CRD420223). The inclusion criteria for selecting the studies were based on the PICO question: "Are skull anatomical structures reliable as alternatives to determine sexual dimorphism compared to the mastoid process?". A literature search for studies was performed in the MEDLINE Scopus, Web of Science, LILACS, and Cochrane Library databases. The Kappa agreement presented an approval level of (k = 0.93). This systematic review analyzed 13 ex-vivo studies published between 2008 and 2023. The risk of bias was considered low in 12 of the studies, and high in 1 study. Based on the findings, it can be concluded that even with the limitations of this systematic review, quantitative and qualitative analyses are essential in sexual identification of human skulls, and different anatomical structures can be used as references in addition to the mastoid process, with high reliability and precision, among them the; glabella, frontal profile, superciliary arch, bizygomatic width, maximum cranial length, and nasal height.

Anatomy of the mastoid triangle and morphometric sex differences

OBJECTIVE OF THE STUDY

This study aimed to quantify the area of the mastoid triangle (MT) and assess potential morphometric differences between males and females.

PATIENTS

The sample consisted of 244 dry human skulls, with biological sex known based on genetic analysis, collected from a medicolegal osteological database from Central-Western Brazil.

MATERIALS AND METHODS

The study was observational, analytical, and cross-sectional. The skulls were analyzed using Heron's equation to calculate the area of the MT. The landmarks connecting each of the sides of the triangle were: Porion (Po)>Mastoidale (Ma)>Asterion (Ast). Morphometric references were calculated and compared based on sex.

RESULTS

The area of the MT was nearly 14% larger in males compared to females (p<0.05). The mean MT area for the right and left sides of males were 684.11±93.25mm² and 668.94±111.95mm², respectively. In females, the mean MT for the right and left sides were 588.93±91.09mm² and 582.88±102.98mm², respectively. Right and left side measurements were significantly different (p<0.05), except for Po-Ast (p=0.232).

CONCLUSION

Morphometric features regarding the MT were slightly different between males and females. Application of the MT as a dimorphic tool should be adjuvant. Moreover, this tool should be considered carefully, especially because the sex-based differences were statistically significant, but discrete between males and females.