Table 3 Radiological results
|  | Rheumatoid arthritis group (n = 32) | p value between before and after | No rheumatoid arthritis group (n = 22) | p value between before and after | p value between RA and non-RA |
|---|---|---|---|---|---|
Atlanto-dental interval (mm) | |||||
 Pre-operation | 7.93 ± 2.32 (3.7–13) |  | 7.90 ± 2.39 (5.1–14.2) |  | 0.9717 |
 Just after operation | 2.47 ± 1.27 (0–5.7) | < 0.001* | 3.79 ± 1.59 (0.5–6.3) | < 0.001* | 0.0059* |
 At final follow-up | 2.41 ± 1.42 (0–6.1) | 0.1480 | 4.49 ± 2.16 (1.5–8.9) | 0.1965 | < 0.001* |
Atlanto-axial angle (degree) | |||||
 Pre-operation | 21.5 ± 9.57 (4.0–42.0) |  | 19.14 ± 2.39 (8.0–35.2) |  | 0.4540 |
 Just after operation | 22.3 ± 9.50 (0–36.0) | 0.1796 | 25.07 ± 5.47 (15.2–36.1) | 0.0849 | 0.3042 |
 At final follow-up | 20.9 ± 8.21 (3.0–36.0) | 0.2437 | 23.0 ± 6.89 (13.4–39.2) | 0.3373 | 0.4073 |
Range of motion of occipito-atlas (degree) | |||||
 Pre-operation | 4.45 ± 3.59 (0–12.0) |  | 8.25 ± 4.90 (3.0–12.0) |  | 0.1171 |
 At final operation | 5.96 ± 5.03 (0–16.4) | 0.8116 | 7.08 ± 6.13 (1.4–22.1) | 0.6721 | 0.5600 |
Atlanto-axial height(mm) | |||||
 Pre-operation | 40.87 ± 18.49 (0–16.6) |  | 43.70 ± 4.42 (37.4–51.2) |  | 0.0899 |
 Just after operation | 43.47 ± 6.30 (24.2–53.5) | 0.1882 | 46.87 ± 4.49 (39.1–53.8) | 0.0018* | 0.0758 |
 At final follow-up | 41.24 ± 6.17 (19.8–52.2) | 0.3385 | 44.33 ± 5.22 (37.4–53.6) | 0.0019* | 0.1051 |
Cervical alignment (C1-C7) | L, St, S, K | Â | L, St, S, K | Â | Â |
Pre-operation | 18, 4, 6, 0 | Â | 9, 2, 9, 0 | Â | 0.5690 |
At final follow-up | 15, 4, 7, 2 | 0.3209 | 8, 2, 10, 0 | 0.7531 | 0.2563 |