Assessing the range of cervical rotation in patients with rheumatoid arthritis after atlantoaxial screw fixation using axial CT.

STUDY DESIGN: Case-series study.

OBJECTIVE: To assess range of cervical rotation possible after atlantoaxial fixation in rheumatoid arthritis (RA) patients using axial CT.

SUMMARY OF BACKGROUND DATA: The atlantoaxial complex is primarily responsible for rotation, and the percentage of global cervical rotation dependent on C1-C2 is 60%. Fusion of C1-C2 was expected to cause a loss of almost half the normal cervical rotation. However, some authors had reported that cervical rotation in RA patients increased after atlantoaxial fixation because of pain relief.

METHODS: Nineteen consecutive patients with atlantoaxial instability secondary to RA who had undergone transarticular fixation were included in our study. Visual analog scale was used for assessment of neck pain. We recorded functional CTs to assess C1 to T1 rotation angles before surgery and 6 months after surgery. The patient actively rotated his neck toward right as far as possible, taking care that the shoulders remained in the horizontal plane.

RESULTS: The average visual analog scale for neck pain decreased significantly from 7 (range, 4-9) before surgery to 3 (range, 0-5) at 6 months after surgery. The average preoperative C1-T1 rotation angles that were measured using axial CT were 80 degrees in total. C1-T1 rotation angle significantly decreased (55% decrease) after surgery, but there was no difference between right and left motion. Average subaxial rotation (C2-T1) was 31 degrees before surgery and did not increase after surgery.

CONCLUSION: All 19 patients with RA and atlantoaxial instability in our study had relief of pain and a significant decrease in the C1-T1 rotation angle after atlantoaxial fixation. Subaxial rotation did not change from before to after the operation.