Evaluation of the bony landmarks in transcondylar approach

The aim of this study is to define the anatomic landmarks which are necessary for transcondylar approach and to determine the importance of these structures during surgical resection.

56 dry skulls were included in this study. Landmarks were detected. Some distances and angles, which were determined before, were measured and the anatomical structures were observed. 21 parameters were examined and analysed in totally 56 dry skulls using 56 foramen magnum, 112 hypoglossal canal and 112 occipital condyles. The landmarks which were used were the anterior and posterior borders of the occipital condyle, the medial and lateral margin of the occipital condyle, basion, opisthion, hypoglossal canal and posterior condylar canal. The measurements were made separately for the right and left sides.

The mean length of the occipital condyle was found as 23.1 mm. The distance between the intracranial edge of the hypoglossal canal and anterior margin of the occipital condyle was measured as 11.2 mm in both sides. The distance between the intracranial edge of the hypoglossal canal and posterior margin of the occipital condyle was measured as 12.5 mm at the right side and 12.6 mm at the left one. The mean length of the hypoglossal canal was measured as 10.5 mm at the right side and 10.6 mm at the left one. 14 hypoglossal canals were divided into two compartments by a septum.

In transcondylar approach, the anatomical landmarks should be well known in order to make a safe occipital condyle resection. The distance between the intracranial edge of the hypoglossal canal and posterior margin of the occipital condyle is important for a safe occipital condyle resection, and it was found to be 12.55 +/-0.05 mm in our study. Approximately 12 mm occipital condyle resection can be made without giving damage to the neural tissue. This value is appropriate to the (1/2) of the occipital condyle.