Surgical approach and number of levels treated.
| No. of Levels Treated | Overall n = 252 (100%) n (%) | Anterior n = 63 (25%) n (%) | Lateral n = 63 (25%) n (%) | Posterior n = 126 (50%) n (%) |
| 1 Level | 189 (75.0) | 39 (61.9) | 46 (73.0) | 104 (82.5) |
| 2 Levels | 61 (24.2) | 22 (34.9) | 17 (27.0) | 22 (17.5) |
| 3 Levels | 2 (0.8) | 2 (3.2) | 0 (0.0) | 0 (0.0) |