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External Occipital Protuberance: Can It Be Used as a Criterion in the Determination of Sex?

NCJ Number
Journal of Forensic Sciences Volume: 48 Issue: 3 Dated: May 2003 Pages: 513-516
I. Nadir Gulekon Ph.D.; H. Basri Turgut Ph.D.
Date Published
May 2003
4 pages
This research sought to determine whether the external occipital protuberance (EOP) can be useful in determining sex, especially in lateral cranium radiographs, when the body has been severely damaged.
The EOP is the insertion site of the nuchal ligament and the neck muscles, so it reflects shape changes that depend on the power of the stretching neck muscles. The fact that the muscle mass/body weight ratio is less in females than males may be the reason why the EOP is more prominent in males with the accordance of the power of neck muscles. To determine the usefulness of the EOP as a determinant of sex, this study used randomly selected right lateral cranium radiographs of 1,000 patients (500 female and 500 male) who were investigated for illness, but found to be normal. Radiographs were taken of females and males 25-50 years old. The EOP was determined by using a classification system modified from Broca. According to this classification, subjects who showed the smooth form of EOP were classified as Type 1; those in whom the EOP was represented as a crest were classified as Type 2; and those who had a spine were classified as Type 3. The second part of the study involved the investigation of dry-skull remains of subjects from the 16th century who had lived in central Anatolia. The sex of the individuals was determined on the basis of cranial morphology and other criteria. The remains of 694 subjects with known sex (323 females and 371 males) were examined for the appearance of the EOP by using the same criteria that were applied in the radiologic investigation. Chi-square statistical analysis was applied to the data of both study groups to determine the difference between sex and EOP types. In the radiographic examination, the incidence of less prominent (Type 1) EOP was found to be 85.4 percent in females and 17.8 percent in males. The spine type (Type 3) EOP was found to be 63.4 percent in males and 4.2 percent in females. The studies of dry-skull remains, however, revealed the incidence of Type 1 EOP to be 67.5 percent in females and Type 3 EOP to be 55.2 percent in males. The crest type (Type 2) EOP was approximately equal in both sexes and thus less valuable for sex determination in both groups. Thus, although the types of EOP can indicate differences in various populations and are not definitive criteria in determining sex, a smooth form of EOP strongly suggests a female identification and a spine form a male identification. A lateral cranium radiograph can therefore be helpful in the determination of sex in forensic cases in which corpses are damaged. 5 figures, 2 tables, and 20 references