Distribution of the 2 groups of buckling (groups A and B) by cervical level.
| Level | No. of Levels (%) | |
| Group A, Buckling≤0.1 mm (n = 798) | Group B, Buckling>0.1 mm (n = 216) | |
| C2-C3 | 156 (19.5) | 13 (6.0) |
| C3-C4 | 136(17.0) | 33 (15.3) |
| C4-C5 | 97 (12.2) | 72 (33.3) |
| C5-C6 | 112 (14.0) | 57 (26.4) |
| C6-C7 | 148 (18.6) | 21 (9.7) |
| C7-T1 | 149 (18.7) | 20 (9.3) |