Evaluation of the obturator foramen as a sex assessment trait

Abstract

Correctly assessing sex from skeletal remains is one of the main elements of creating a biological profile. Many traits allow for this, the obturator foramen being one. However, research on its accuracy has provided mixed results. This study examines the obturator foramen using a 5-point grading scale to assess the degree of sexual dimorphism in four known age and sex skeletal collections from the UK and South Africa. Overall, sexual dimorphism was found in the obturator foramen when using the new scoring system; however, accuracies for correct sex classification ranged from ~ 46 to ~ 75%. Considering its wide range in accuracy rates across the four samples and difficulty in identifying the subtle changes in morphology, the obturator foramen should only be used as part of a multifactorial assessment of sex.

Keywords: Forensic anthropology; Obturator foramen; Pelvis; Sex determination; Sexual dimorphism.

Fig. 1

CAS 2070 Female, 35 years old, Spitalfields, London, UK (Natural History Museum, UK) (image taken by author). Dorsal view of the left anterior pelvis. A Os pubis, B ischiopubic ramus, C obturator groove, and D iliopubic ramus

Fig. 2

Morphological scoring of the obturator foramen (dorsal view) ranging from female (score 1) to male (score 5)

Fig. 3

Illustration of the landmarks used A anterior superior angle (solid circle) and anterior inferior angle (dashed circle) are more defined/angular in score 2 than in score 3. B Posterior inferior angle (solid circle) is more defined in score 3 than in score 4. In score 3, the anterior superior angle (dashed circle) is present whilst in score 4, it is not

Fig. 4

Frequency of obturator foramen scores. A Spitalfields, B South African White, C South African Black, and D South African Coloured