Demographic data.
| Variable | n (%) or Mean (SD) |
| N | 49 (100%) |
| Age, y | 61.4 (11.4) |
| Woman | 30 (61.2%) |
| Body mass index (kg/m2) | 31.3 (5.1) |
| Caucasian | 38 (77.6%) |
| Not Hispanic | 48 (98.0%) |
| Operative level | |
| L1–L2 | 0 (0%) |
| L2–L3 | 3 (6.1%) |
| L3–L4 | 10 (20.4%) |
| L4–L5 | 27 (55.1%) |
| L5–S1 | 9 (18.4%) |