Foramen magnum, occipital condyles and hypoglossal canals morphometry: anatomical study with clinical implications

Abstract

Background: Current study examines morphometric alterations of the foramen magnum (FM), occipital condyles (OCs) and hypoglossal canals (HCs) and highlights all the morphometric parameters of the FM area that present side asymmetry, gender dimorphism and are affected by the ageing.

Materials and methods: One hundred and forty-one (73 male and 68 female) Greek adult dry skulls were examined.

Results: Short and long OCs were detected in 27.7% and 26.2%. A combination of short OCs and long HCs was presented in 27.5%. A complete septum was found in 23.6% of the HCs and osseous spurs in 12.9%. Side asymmetry was detected regarding the HCs length (p = 0.046), the maximum extracranial (p = 0.001) and minimum intracranial (p = 0.001) diameters. Mean FM anteroposterior and transverse diameters, FM perimeter and FM surface area were significantly larger in male than in female skulls (p = 0.001 for each parameter). Similarly, the OCs length (right, p = 0.004 and left, p = 0.024) and width (right, p = 0.008 and left, p = 0.006) the left distance HC-OC posterior border (p = 0.048), the anterior (p = 0.011) and posterior (p = 0.001) intercondylar distances and the HCs right length (p = 0.046) were significantly greater in males. A significant decrease was observed with ageing in FM anteroposterior diameter (p = 0.038), FM surface area (p = 0.05), anterior intercondylar distance (p = 0.014) and HC-OC posterior border (p = 0.013).

Conclusions: The study confirmed that only specific HC dimensions showed side asymmetry (HCs maximum extracranial and minimum intracranial diameters and HCs length), gender dimorphism (HCs right length and left distance HC-OC posterior border) and age influence (HC-OC posterior border and HC left extracranial minimum diameter) among young, adults and elderly individuals. FM and OCs dimensions presented gender dimorphism and the age influenced only FM anteroposterior diameter and surface area and the anterior intercondylar distance. The safe zone of OCs drilling in Greeks, calculated by the distance HC-OC posterior border represents the maximum HC depth and is among the lowest values reported in the literature. The significant decrease of this distance with ageing confirms the existence of a drilling safe zone for young, adults and elder individuals. Regarding OCs length, the same probability exists dealing with a short or a long OC during condylectomy. Before planning a transcondylar approach, the coexistence of short OCs and long HCs should be taken into account. These outcomes will be useful for a safe surgery in the craniocervical region in Greeks.

Keywords: age; asymmetry; foramen magnum; gender; hypoglossal canal; occipital condyle.