Introduction: The posterior cervical approach is the most accepted approach to achieve the atlantoaxial stabilization after odontoidectomy. The primary disadvantage of this approach is that it is conducted as a second stage procedure. The goal of the current study is to assess the surgical feasibility and biomechanical results of an endoscopic endonasal surgical technique for C1-C2 fixation that may eliminate the need for posterior fixation after the odontoidectomy.
Methods: The first step of the study was to perform dissections in ten silicon-injected fixed cadaver heads to identify relevant surgical landmarks. The second step of the study was a quantitative radiographic analysis on ten reconstructed (custom software) adult cervical spine CT scans to identify the optimal screw entry point and trajectory. The third step was a biomechanical analysis of fourteen upper cervical cadaveric specimens (OC-C2) in intact and fusion conditions. A half of specimens received anterior transarticular screws and the second half received the posterior transarticular screws.
Results: The mean distance between both tubal elevations was 19.5 mm (16.8-23.1). The total vertical working distance was 45.9mm (42.3- 48.7) and the total horizontal working distance was 25.7 mm (21.8- 28.9). Radioanatomic analysis suggested that the optimal screw entry point was on the anterior aspect of the C1 lateral mass and the screw trajectory was inferiorly and laterally directed. Custom design angled instrumentation was crucial for drilling and screw placement. Based on normalized ROM, there were no significant differences (P > 0.05) between anterior and posterior fusion technique during any direction of motion.
Conclusions: The current study demonstrates the feasibility of an anterior technique for C1-C2 fusion. This novel technique may have clinical utility by abrogating the need for a second stage posterior fixation operation in certain patients undergoing odontoidectomy. The biomechanical tests demonstrated comparable stability to posteriorly placed transarticular screws.
Patient Care: The proposed technique prevents risks related to the posterior cervical approach after odontoidectomies.
Learning Objectives: By the conclusion of this section, participants should be able to identify a novel technique for atlantoaxial fusion.
References: 1. Alfieri A, Jho HD, Tschabitscher M. Endoscopic endonasal approach to the ventral cranio-cervical junction: anatomical study. Acta Neurochir (Wien ). 2002; 144:219-225.
2. Kassam AB, Snyderman C, Gardner P, Carrau R, Spiro R. The expanded endonasal approach: a fully endoscopic transnasal approach and resection of the odontoid process: technical case report. Neurosurgery. 2005; 57:E213.
3. Dickman CA, Crawford NR, Brantley AG, Sonntag VK. Biomechanical effects of transoral odontoidectomy. Neurosurgery. 1995; 36:1146-1152.
4. Dickman CA, Locantro J, Fessler RG. The influence of transoral odontoid resection on stability of the craniovertebral junction. J Neurosurg. 1992; 77:525-530.
5. Wu JC, Huang WC, Cheng H et al. Endoscopic transnasal transclival odontoidectomy: a new approach to decompression: technical case report. Neurosurgery. 2008; 63:ONSE92-ONSE94.
6. Papagelopoulos PJ, Currier BL, Hokari Y et al. Biomechanical comparison of C1-C2 posterior arthrodesis techniques. Spine (Phila Pa 1976 ). 2007; 32:E363-E370.
7. Kandziora F, Mittlmeier T, Kerschbaumer F. Stage-related surgery for cervical spine instability in rheumatoid arthritis. Eur Spine J. 1999; 8:371-381.
8. Crawford NR, Hurlbert RJ, Choi WG, Dickman CA. Differential biomechanical effects of injury and wiring at C1-C2. Spine (Phila Pa 1976 ). 1999; 24:1894-1902.