Patient and treatment characteristics.
| Characteristic | Value (N = 33) |
| Age, y, mean (range) | 64.9 (34–82) |
| Female, n (%) | 18 (55) |
| Body mass index, kg/m2, mean (range) | 29.5 (20.0–38.5) |
| Current smoker, n (%) | 4 (12) |
| Previous posterior fusion level, n (%) | |
| L5-S1 (1-level) | 8 (24) |
| L4-S1 (2-level) | 15 (46) |
| L3-S1 (3-level) | 8 (24) |
| L2-S1 (4-level) | 2 (6) |
| Time from fusion to ASD, y, mean (range) | 7.8 (1–25) |
| ASD pathology (35 devices), n (%) | |
| Degenerative spondylolisthesis | 12 (34) |
| Foraminal stenosis | 10 (29) |
| Canal stenosis | 8 (23) |
| Degenerative disc disease | 5 (14) |
| ASD level treated (35 devices) | |
| L1-L2, n (%) | 4 (11) |
| L2-L3, n (%) | 10 (29) |
| L3-L4, n (%) | 14 (40) |
| L4-L5, n (%) | 7 (20) |
| Psoas retraction time, min, mean (range) | |
| Total time | 30.8 (15–40) |
| Time with retractor open to 22 mm | 14.4 (8–24) |
| Time with retractor open to 25 mm | 13.9 (7–22) |
ASD, adjacent segment disease.