Posterior atlantoaxial facet screw fixation
✓ Eighteen patients with atlantoaxial instability were treated with posterior atlantoaxial facet screws to obtain immediate rigid fixation of C1–2. Of these 18 patients, instability occurred due to trauma in nine, rheumatoid arthritis in six, neoplasms in two, and os odontoideum in one. Four patients presented with nonunion after failed C1–2 wire and graft procedures. In all cases in this series the screw fixations were augmented with an interspinous C1–2 strut graft which was wired in place to provide three-point stabilization and to facilitate bone fusion. In every case fixation was satisfactory, and C1–2 alignment and stability were restored without complications due to instrumentation. One patient died 3 months postoperatively from metastatic tumor; the spinal fixation was intact. All 17 surviving patients have developed osseous unions (mean follow-up period 12 months, range 6 to 16 months). Posterior atlantoaxial facet screw fixation provides immediate multidirectional rigid fixation of C1–2 that is mechanically superior to wiring or clamp fixation. This technique maximizes success without the need for a supplemental rigid external orthosis, and is particularly useful for pseudoarthrosis.