Description of the study population.
| Characteristic | Measure |
| Age, y, mean (range) | 47.8 (20–77) |
| Body mass index, kg/m2, mean (range) | 28.0 (20.4–40.6) |
| Gender, n (%) | |
| Women | 30 (51.7%) |
| Men | 28 (48.3%) |
| Prior lumbar spine surgery, n (%) | 25 (43.1%) |
| Level(s) implanted, n (%) | |
| L4-L5 | 11 (19.0%) |
| L5-S1 | 44 (75.9%) |
| L4-L5 and L5-S1 | 2 (3.4%) |
| L3-L4 and L5-S1 | 1 (1.7%) |