C2-3 Fusion, C3-4 Cord Compression and C1-2 Posterior Facetal Instability: An Evaluation of Treatment Strategy Based on Four Surgically Treated Cases

Abstract

Study design: Four patients had C2-3 vertebral fusion and radiologically demonstrated cord compression at C3-4 level related to disc bulge with or without association of osteophytes and C1-2 posterior facetal dislocation. The outcome of treatment by atlantoaxial and subaxial facetal fixation is discussed.

Purpose: The article evaluates the significance of atlantoaxial facetal instability in cases having C2-3 vertebral fusion and cord compression at the level of C3-4 disc.

Overview of literature: C2-3 vertebral fusions are frequently encountered in association with basilar invagination and chornic atlantoaxial dislocations. Even when basilar invagination and atlantoaxial dislocation are not identified by conventional parameters, atlantoaxial instability can be the nodal point of pathogenesis in cases with C2-3 vertebral fusion.

Methods: Between June 2013 and November 2014 four patients having C2-3 fusion presented with progressive symptoms of myelopathy that were related to cord compression at the level opposite the C3-4 disc space. Further investigations revealed C1-2 posterior facetal dislocation.

Results: All patients were males. Ages ranged from 18 to 50 years (average, 36 years). All patients were treated by atlantoaxial facetal plate and screw, and subaxial single or multi-segmental transarticular screw fixation. Follow-up (average, 15 months) using a recently described clinical grading system and the Japanese Orthopaedic Association scoring system confirmed marked improvement of symptoms.

Conclusions: Identification and treatment of atlantoaxial facetal instability may be crucial for a successful outcome in cases having C2-3 fusion and high cervical (C3-4) disc related cord compression.

Keywords: Atlantoaxial dislocation; High cervical disc prolapse; Transarticular fixation.

Fig. 1. Images of a 50-year-old male patient. (A) T2-weighted magnetic resonance imaging (MRI) shows C2–3 fusion and altered cord signal opposite C3–4 disc space. There is no evidence of any cord compression at the level of tip of odontoid process. (B) Sagittal cut of MRI at the level of facets showing Goel type B atlantoaxial facetal instability. (C) Computed tomography (CT) scan showing the C2–3 fusion. (D) Three-dimensional (3D) CT scan of the cervical spine showing the fusion of C2–3 vertebrae and the facets. (E) Posterior view of the 3D CT scan showing the bifid arch of atlas. (F) Postoperative CT scan findings. (G) Postoperative scan shows fixation of C1–2 (lateral mass plate and screw technique) and C3–4 and C4–5 by transarticular method of fixation.