Congenital Agenesis of the Obturator Foramen in an Asian Population and Its Clinical Significance

The obturator foramen, an ovoid opening in the hip bone formed by the ischium and pubis, allows passage of the obturator artery, vein, and nerve through the obturator canal. Mostly covered by the obturator membrane, its congenital agenesis or partial underdevelopment is extremely rare and scarcely documented, yet it carries significant implications for pelvic surgery, orthopedic, vascular procedures, and radiological interpretation.

This study aimed to determine the prevalence, morphological characteristics, and clinical relevance of congenital agenesis of the obturator foramen in an Asian population.

The study was conducted between 2019 and 2025 in the department of Anatomy on 228 dried human hip bones belonging to 114 pelvises, irrespective of age and sex. All hip bones were examined macroscopically for evidence of congenital agenesis complete or incomplete of the obturator foramen. Thickness measurements of the abnormal bony plate replacing the foramen were recorded using digital callipers. High-resolution photographs were taken for documentation.

Overall, congenital agenesis complete, incomplete, or mixed was observed in 15 of 114 pelvises (13.2%). Unilateral complete agenesis of the obturator foramen and canal was identified in 3 right-sided (2.6%) and 4 left-sided (3.5%) hip bones, with an average bony plate thickness of 2.1 mm. Unilateral complete agenesis of the obturator foramen with a narrowed bony obturator canal occurred in 3 right-sided (2.6%) and 3 left-sided (2.6%) hip bones, demonstrating an average thickness of 2.2 mm. One pelvis (0.9%) exhibited mixed agenesis complete on the right and incomplete on the left, with an average thickness of 2.0 mm. In addition, one hip bones (0.9%) demonstrated bilateral complete agenesis of the obturator foramen and canal, showing a markedly increased average thickness of 1.9 mm. The thinnest bony plate recorded in the present study measured 0.5 mm.

Congenital agenesis of the obturator foramen is an exceptionally rare anatomical variant in the studied Asian population. Awareness of this anomaly is clinically important, as it can alter pelvic biomechanics, obscure radiological interpretation, and affect the surgical approach to the obturator region. Detailed anatomical knowledge may help prevent intraoperative complications and improve diagnostic accuracy.