Sex Determination Using Mastoid Process Measurement in Thais
Chayanit Manoonpol MS*, Vasana Plakornkul DVM, MS*
Affiliation : * Department of Anatomy, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand
Background : Analysis of skeleton is necessary for sex determination. There are several pieces of bone that are used such as
pelvic bone and zygomatic arch etc. In the fieldwork of physical anthropologist and forensic physician, the skull or some
pieces of the skull can be very useful. In the skull, the mastoid process is a compact and permanent process. Craniometric
measurements of mastoid process are interesting parameters to distinguish sex.
Objective : To study the craniometric measurements of mastoid process of dry skulls in Thais and provide a method for sex
determination.
Material and Method: One hundred normal skulls of Thais from the central region, 60 male and 40 female, were studied.
The measurement of mastoid process between the three points, porion (po), mastoidale (ma), and asterion (as) were made.
The three distances (po-ma, ma-as, po-as) were recorded (mm) and the mastoid triangular areas were calculated by using
Heron’s formula (mm2). The student’s t-test and linear discriminant analysis were used for data analysis.
Results : The means of mastoid dimensions and mastoid triangular area in male are significantly larger than those of the
female (p < 0.01). The linear discriminant analysis shows that using the mastoid process dimensions and mastoid triangular
area for determining sex in Thais are convincing. The average accuracy is 67.00 to 76.90%. The better mastoid dimension
is ma-as of the right mastoid process. It shows a high average accuracy at 76.90%.
Conclusion : Means of the mastoid dimensions and mastoid triangular area of Thai skulls (whole skull or fragments) provide
an accurate method for determining sex.
Keywords : Physical anthropology, Mastoid process, Sexual dimorphism, Thai skull
