Unilateral posterior atlantoaxial transarticular screw fixation

Abstract

Bilateral posterior C 1-2 transfacet screw placement with associated posterior bone graft wiring is the accepted treatment for patients with atlantoaxial instability. This technique was modified to treat 19 patients with atlantoaxial instability and unilateral anomalies that prevented placement of a screw across the C1-2 facet. In these cases, a single contralateral transarticular screw was placed in conjunction with interspinous bone graft wiring to avoid neural or vertebral artery injury and to provide C1-2 stability. Postoperatively, all 19 patients were placed in Philadelphia collars (mean immobilization 8 weeks, range 6-12 weeks). Unilateral C1-2 facet screw fixation was needed for the following reasons: a high-riding transverse foramen of the C-2 vertebra present in 13 patients (left side in eight, right side in five), poor screw purchase in two (left side in both), screw malposition in one (left side), severe degenerative arthritis in one (right side), neurofibroma in one (right side), and fracture of the C-1 lateral mass in one (left side). Six weeks postsurgery, one patient presented with a broken screw and required occipitocervical fusion with a Steinmann pin and wire cable from the occiput to C-3 to achieve solid fusion. Solid fusions were achieved in the other 18 patients (mean follow-up period 31 months, range 14-54 months); there was no delayed screw breakage, wire breakage, or spinal instability. There were no operative or postoperative neurological or vascular complications. The authors' experience demonstrates that unilateral C1-2 facet screw fixation with interspinous bone graft wiring is an excellent alternative in the treatment of atlantoaxial instability when bilateral screw fixation is contraindicated.

Transarticular screw fixation for osteoarthritis of the atlanto axial segment

“…Confirming previous studies [16,26], the present series showed that solid fusion can be achieved even if only one screw is placed ideally (e.g. following the inadvertent misplacement of the screw on the opposite side) and is combined with appropriate midline bone grafting.…”

Unilateral Posterior Atlantoaxial Transarticular Screw Fixation in Patients with Atlantoaxial Instability : Comparison with Bilateral Method

“…It is the most effective biomechanical technique to attain C1-2 stability, and is superior to conventional wiring methods by virtue of more rigid fixation 18) . Solid atlantoaxial fusion has been reported in 80 to 100% of patients who were treated with this method 14,18) .…”

“…It is the most effective biomechanical technique to attain C1-2 stability, and is superior to conventional wiring methods by virtue of more rigid fixation 18) . Solid atlantoaxial fusion has been reported in 80 to 100% of patients who were treated with this method 14,18) . However, bilateral TAF across the C1-2 may be contraindicated or impossible in up to 20% of patients because of its structural disfigurements such as anomalous course of the vertebral artery (VA), comminuted fractures of C-1 or C-2, or other pathological processes 14) .…”

“…Simultaneous bilateral posterior transarticular screw fixation (TAF) and bone grafting with wire loop provides immediate, rigid internal fixation for atlantoaxial instability (AAI) 18) . It is the most effective biomechanical technique to attain C1-2 stability, and is superior to conventional wiring methods by virtue of more rigid fixation 18) .…”

Left-right axial rotation within C1–2 after implant removal

“…Some advantages connected with this technique have been described: first, it can be used even in the case of a so-called high-riding vertebral artery, which has been described to be as frequent as 10%-25%. 1,19,24 Second, repositioning of an anteriorly placed fragment is easy by soft tension applied to the atlas, especially if combined with pressure to the spinous process of C-2. Third, it was hypothesized that the segmental mobility within C1-2 could be preserved in case of implant removal.…”