| Timing for evaluation of back pain | Range of VAS |
| Before surgery | 4 - 9 |
| 1 day postoperative | 4 - 7 |
| 1 week postoperative | 3 - 5 |
| 1 month postoperative | 0 - 4 |
| 3 months postoperative | 0 - 2 |
| 6 months postoperative | 0 |