Morphological study of the foramen magnum and occipital condyle and its surgical implications in transcondylar approach

Abstract

The transcondylar approach is being increasingly used to access lesions ventral to the brain stem and cervicomedullary junction. Understanding the anatomy of the occipital condyles is important for this approach. The present work aimed to clarify the morphometric data of the occipital condyle and its importance in transcondylar approach. The study was performed on 200 occipital condyles of 100 adult human dry skulls of unknown age and sex. Metric and morphological analysis was performed for the specimens. The parameters were, the length, width, height, the anterior and posterior inlercondylar distances and the distances from the occipital condyle to the midline of the foramen magnum. En addition, the different locations of the hypoglossal canal orifices relative to the occipital condyle were assessed. The different shapes of the occipital condyles and their rates were detected. The length, width and height of the occipital condyle were found to be 23.5, 13.58 and 9.64 mm in the right and 23.75, 13.62 and 9.5mm in the left respectively. The anterior and posterior intercondylar distances were 20.64 and 41.4mm respectively. The intracranial orifice of hypoglossal canal was found to be present against the junction of the 2nd and quarter or against the 3rd quarter of the occipital condyle in 65%. The extracranial orifice of the hypoglossal canal was found to be present against the junction of the 1st and 2nd quarter or against the 2d quarter of the occipital condyle in 69%. The more frequent type of occipital condyle detected is kidney shaped. It could be concluded that, the safest area to be drilled in the occipital condyle is the posterior quarter (4.5-78mm from the posterior end) as there is no location for the hypoglossal canal orifice was found against this area. In the other locations the extent of bony resection of the occipital condyle can be anticipated by the available recent radiological techniques by using the meicioiiJ5örphometric parameters.