Introduction: Atlantoaxial fixation remains technically challenging. Atlantoaxial arthrodesis can be complicated by pseudoarthroses caused by insufficient surface area for fusion and chronic postoperative pain resultant from C2-nerve-root sacrifice. This study presents a novel, safe, and reliable C1-2 fixation technique using a C1 lateral mass and C2 pedicle screw construct with intra-articular-arthrodesis to maximize surface area under direct axial load, while sparing the C2-nerve-root.

Methods: A retrospective review was performed on 39 patients with radiographically documented C1-2 instability who underwent the described procedure from 2000-2011 (mean age 63.62 years; range 27-83 years; 20fm/19m). Underlying causes of C1-2 instability included degenerative facet disease (23.08%), rheumatoid arthritis (12.82%), os odontoideum (10.26%), neoplasm (10.26%), and odontoid fracture (23.08%). Eleven patients had myelopathy (28.21%). Comorbidities included hypertension (43.59%), hyperlipidemia (20.51%), hypothyroidism (20.51%), and heart disease (33.33%). All patients underwent isolated C1 lateral mass and C2 pedicle screw placement with fluoroscopy/image-guidance. The C1-2 joint was accessed by retracting the C2-nerve-root superiorly and drilling out the joint using a high-speed burr and resultant cavity packed with a combination of local autologous bone with BMP. Outcome measures included radiographically demonstrated fusion/alignment, Ranawat’s Neural and Pain Levels. Data were analyzed using Fischer’s, Mann-Whitney, ANOVA, and Bonferroni, as appropriate.

Results: Radiographic/clinical evidence of C1-2 fusion/stability was achieved in all patients at mean 7.45 months (range 1–80.73). Mean postoperative hospital stay was 4.85 days (range 1–19). Mean operative time was 165.52 minutes (range 87–414). Mean EBL was 363.97cc (range 50-1100). No vertebral artery or spinal cord injuries occurred. In all patients, occipital/neck pain and neural deficits improved, with a significant (P<0.00001) reduction (88.99%) in pain.

Conclusions: Atlantoaxial fusion using C1 lateral mass and C2 pedicle screws with C2-nerve-sparing C1-2 intra-articular arthrodesis is a safe and reliable technique for C1-2 fusion, suitable for traumatic, neoplastic, degenerative, and other causes of atlantoaxial instability.

Patient Care: C1-2 instability remains a difficult problem to treat surgically. The use of C1 lateral mass and C2 pedicle screws by Harms et al. (2001) improved on high non-union rates sustained in early posterior wiring procedures. A more recent modification of the Harms procedure (Aryan et al., 2008) entailed curette arthrodesis requiring sacrifice of the C2 nerve root bilaterally. However, this technique can lead to occipital headaches associated with C2 nerve root sacrifice. We present a novel alternative technique for C1-2 fixation that does not require sacrificing the C2 nerve root. During the C1 lateral mass screw placement procedure, injury can occur to the exiting C2 nerve root. Due to proximity, the placed C1 screw can irritate the C2 nerve root, resulting in pain and discomfort for the patient. Our technique employs a C2 nerve-sparing mobilization step, in which the C2 nerve root is lifted superiorly out of harm’s way during drilling the C1-2 facet joint. Intraoperative fluoroscopy and image-guidance systems are also key to establishing proper screw placement trajectory. This novel procedure can potentially decrease pain and discomfort for the patient while still achieving a high rate of fusion.

Learning Objectives: C2 nerve-sparing mobilization is a critical step in the C1-2 joint intra-articular-arthrodesis that can be employed to achieve significant reduction in patient pain levels. The C2 nerve root is lifted superiorly out of harm’s way during drilling the C1-2 facet joint.

References: 1. Aryan HE et al. J Neurosurg Spine. 2008;8(3):222-229. 2. Brooks AL et al. J Bone Joint Surg Am. 1978;60(3):279-284. 3. Dickman CA et al. J Neurosurg. 1991;74:190-198. 4. Harms J et al. Spine 2001;26:2467-2471. 5. Tokuhashi Y et al. Spine 2000;25(3):337-341.