POSTERIOR C1-C2 TRANSARTICULAR SCREW FIXATION FOR ATLANTOAXIAL ARTHRODESIS

OBJECTIVE: To assess the outcomes associated with C1-C2 transarticular screw fixation. METHODS: The clinical outcomes of 121 patients treate d with posterior C1-C2 transarticular screws and wired posterior C1-C2 autologous bone struts were evaluated prospectively. Atlantoaxial ins tability was caused by rheumatoid arthritis in 48 patients, C1 or C2 f ractures in 45, transverse ligament disruption in 11, os odontoideum i n 9, tumors in 6, and infection in 2. RESULTS: Altogether, 226 screws were placed under lateral fluoroscopic guidance. Bilateral C1-C2 screw s were placed in 105 patients; each of 16 patients had only one screw placed because of an anomalous vertebral artery (n = 13) or other path ological abnormality. Postoperatively, each patient underwent radiogra phy and computed tomography to assess the position of the screw and he aling. Most screws (221 screws, 98%) were positioned satisfactorily. F ive screws were malpositioned (2%), but none were associated with clin ical sequelae. Four malpositioned screws were reoperated on (one was r epositioned, and three were removed). No patients had neurological com plications, strokes, or transient ischemic attacks. Long-term follow-u p (mean, 22 mo) of 114 patients demonstrated a 98% fusion rate. Two no nunions (2%) required occipitocervical fixation. In comparison, our C1 -C2 fixations with wires and autograft (n = 74) had an 86% union rate. CONCLUSION: Rigidly fixating C1-C2 instability with transarticular sc rews was associated with a significantly higher fusion rate than that achieved using wired grafts alone. The risk of screw malpositioning an d catastrophic vascular or neural injury is small and can be minimized by assessing the position of the foramen transversaria on preoperativ e computed tomographic scans and by using intraoperative fluoroscopy a nd frameless stereotaxy to guide the screw trajectory.