Odontoidectomy through posterior midline approach followed by same sitting occipitocervical fixation: A cadaveric study

Abstract

Object: Atlantoaxial instability with irreducible odontoid process is one of the challenges in spine surgery. These lesions are commonly treated through anterior transoral approach which is followed by posterior atlantoaxial fusion. However, there are still many limitations, especially cerebrospinal fluid fistula with subsequent life-threatening infection, difficulty in cases with limited opening of mouth due to temporomandibular arthritis or anomalies of naso-oropharynx. Türe et al. used the extreme lateral transatlas approach for the removal of odontoid. In this study, we applied the transatlas approach but through posterior midline incision aiming to evaluate its safety and feasibility.

Methods: In four silicon injected, formalin-fixed cadaver heads, posterior removal of the odontoid was done through the familiar midline incision and subperiosteal muscle separation and elevation of muscles as on unit followed by microscopic exposure and mobilization of the vertebral artery after opening of the foramen transversarium of atlas followed by drilling of lateral mass and odontoidectomy. Occipitocervical stabilization was done between the occiput and C2, C3 (C1 lateral mass screw can be added in the contralateral side for better stabilization).

Results: Unilateral excision of the lateral mass of atlas after mobilization of the vertebral artery provided safe and excellent exposure of the odontoid process in the four cadaver heads without injury to vertebral artery or retraction of the dura.

Conclusion: Posterior removal of the odontoid can be done safely through wide and sterile operative field, and occipitocervical fixation performed at the same sitting without need for another operation and hence avoids the risk of cord injury from repositioning.

Keywords: Craniocervical junction; extreme lateral-transatlas approach; removal of the odontoid.

Figure 1

The view provided after muscle separation

Figure 2

The dissector introduced in C1 foramen transversarium

Figure 3

Opening of C1 foramen transversarium

Figure 4

Mobilization of the vertebral artery

Figure 5

Drilling of C1 lateral mass

Figure 6

Lateral view shows the exposure of the odontoid process

Figure 7

Complete removal of the odontoid process and decompression of spinal dura

Figure 8

(a and b) The entry points for screws placement in occiput and C2 pedicle and C3 lateral mass and occipitocervical stabilization