C1-C2 transarticular screw fixation for atlantoaxial instability due to rheumatoid arthritis: a seven-year analysis of outcome.

STUDY DESIGN.: Observational study. Retrospective analysis of prospectively collected data. OBJECTIVE.: The purpose of this article was to report long-term (minimum 7 years) clinical and radiologic outcome of our series of patients with Rheumatoid Arthritis who underwent transarticular screw fixation to treat atlantoaxial subluxation. SUMMARY OF BACKGROUND DATA.: The indications for intervention in patients with atlantoaxial instability are pain, myelopathy, and progressive neurologic deficit. The various treatment options available for these patients are isolated C1-C2 fusion, occipitocervical fusion with or without transoral surgery. Review of current literature suggests that C1-C2 transarticular screw fixation has significant functional benefits, although there is discrepancy in this literature regarding improvement in function following surgery. METHODS.: Myelopathy was assessed using Ranawat myelopathy score and Myelopathy Disability Index. Pain scores were assessed using Visual Analogue Scale. The radiologic imaging was assessed and the following data were extracted; atlanto-dens interval, space available for cord, presence of signal change on T2 weighted image, and fusion rates. RESULTS.: Thirty-seven patients, median age 56, were included in the study. Average duration of neck symptoms was 15.8 months. Average duration of rheumatoid arthritis before surgery was 20.6 years. Preoperative symptoms: suboccipital pain in 26 patients; neck pain, 32; myelopathy, 22; and 5 were asymptomatic. After surgery: suboccipital pain, 2; neck pain, 3; and myelopathy, 10. Ninety percent patients with neck and suboccipital pain improved after surgery in their Visual Analogue pain scores, with all of them having >50% improvement in VAS scores (6.94-2.12 [P < 0.05]).Preoperative Ranawat grade was as follows: grade 1 in 15 patients, grade 2 in 7, and grade 3a in 14, grade 3b in 1.After surgery: grade 1 in 27 patients, grade 2 in 7, grade 3a in 1, and grade 3b in 2. The mean myelopathy score improved after surgery (59.62-32.75, P < 0.05).The space available for the cord was improved in 63%, unchanged in 33%, and worse in 4%.Twenty-seven percent had T2 signal change and 18% had cervicomedullary compression; 97% had bony fusion. BILATERAL SCREWS WERE USED IN 33 PATIENTS AND UNILATERAL SCREWS IN 4 PATIENTS (ABERRANT VERTEBRAL ARTERY).: Computer image guidance was used in 73%. CONCLUSION.: C1-C2 transarticular screw fixation is a safe technique for atlantoaxial subluxation for patients with rheumatoid arthritis. This study clearly demonstrates improvement in Visual Analogue Scale, Ranawat grading and the Myelopathy Disability Index even at long-term follow up.