Morphological variations and morphometric analysis of the foramen magnum in adult human skulls: An osteological study

Background: The foramen magnum (FM), the largest cranial base opening, serves as a vital passage between the cranial cavity and vertebral canal. Its morphology and morphometry are clinically relevant in neurosurgery, radiology, forensic anthropology, and craniovertebral junction assessment. Aims and Objectives: This study aimed to evaluate morphological variations and analyze morphometric characteristics of the FM in adult human skulls. Materials and Methods: A cross-sectional osteological study was conducted on 100 adult dry human skulls from the Departments of Anatomy, Rani Durgavati Medical College, Banda, and KGMU, Lucknow.Anteroposterior diameter (APD) and transverse diameter (TD) were measured using a digital Vernier caliper. The FM index (FMI) and surface area were calculated using standard formulae. Statistical analysis was performed using the Statistical Package for the Social Sciences version 26.0, with P<0.05 considered significant. Results: Oval-shaped FM was the most common morphology (38%), followed by round (18%) and egg-shaped (15%). The mean APD was 34.7±3.0 mm, TD 29.0±2.7 mm, and FMI 1.19±0.06. Significant differences were observed in APD (P=0.012), TD (P=0.019), and surface area (P<0.001) among different shapes. Strong positive correlations were noted between APD and surface area (r=0.842, P<0.001) and between TD and surface area (r=0.791, P<0.001). Conclusion: The oval shape predominates and exhibits the largest dimensions. Significant associations between FM shape and morphometric parameters underscore their anatomical and clinical importance in neurosurgical, radiological, and forensic applications.