AN ANATOMICAL PERSPECTIVE OF HUMAN OCCIPITAL CONDYLES AND FORAMEN MAGNUM WITH NEUROSURGICAL CORRELATES

Objectives: Knowledge of condylar anatomy helps the surgeon in making important decisions regarding extent and direction of condylar drilling and minimizing injury and retraction of neural structures. Important preoperative information includes length, width, axis/directions and overriding of occipital condyle in foramen magnum, relationships of condyles to foramen magnum and to hypoglossal canal. The anteroposterior and transverse diameters of foramen magnum and amount of overriding of occipital condyle in foramen magnum are useful in calculating area of surgical field. The present study aims to provide important anatomical parameters for the far lateral transcondylar approach. Methods: The morphometric analysis of human occipital condyles and foramen magnum in 126 dried human skulls and 50 separated occipital bones was performed. The parameters significant to the far lateral transcondylar approach were measured using a digital vernier caliper. In addition, morphometric analysis was also done on 40 patients using thin section CT scans. The paired ‘t’test was performed. Results: The difference between the measurements for the right side and left side and those done on CT scans and using vernier calipers on bones came out to be statistically insignificant (p>0.05). Conclusion: The far lateral transcondylar approach provides better exposure of the ventrolateral foramen magnum and inferior clivus. Lesion removal from this site can be considerably made easier by utilizing a shorter and widened angle of exposure. Preoperative assessment using CT imaging facilitates the far lateral transcondylar approach without damage to vital functional structures.