Applied anatomy for the prevention of the vertebral artery injury during the procedure of far-lateral trans-condylar approach

Objective: To supply microsurgical anatomic materials for protecting vertebral artery during the procedure of the far-lateral trans-condylar approach. Method: Twenty adult cadaveric head specimens fixed with 10% formalin were studied. Results: Transverse process of atlas, ventral ramus of C2, levator scapulae muscle, vertebral venous plexus which surrounding vertebral artery, rectus capitis lateralis were important signs for identifying the second and third segments of vertebral artery. The distances between the transverse foramina of the atlas and axis were 15. 3±1. 6 mm(left) and 15. 8±2. 2 mm (right). The distances from the middle point of the posterior margin of the foramen magnum to the site of the vertebral artery penetrating the dura were 21. 6± 2. 0 (left) and 21. 5±2. 0 (right). Above the posterior arch of the atlas, the vertebral artery looped posteriorly and the outer width of the loop were 17. 9± 3. 2 mm (left) and 17. 6±3. 2 mm (right); its inside width were 9. 8± 2. 5 mm (left); 9. 8± 2. 2 mm (right); its height to the posterior arch of the atlas were 7. 4± 2. 3 mm (left) and 6. 3±3. 3 mm (right). Conclusions: The anatomic materials of the second, third and fourth segments of vertebral artery are very important for protecting the artery and helpful for the far-lateral trans-condylar surgical approach.