Patient demographic characteristics between the national database and institutional cohort.
| American College of Surgeons National Surgical Quality Improvement Program (N = 13,678) | Institutional Registry (N = 940) | P Value | |
| Age, y | |||
| 18–30 | 2.2% | 2.0% | |
| 31–50 | 17.1% | 22.1%a | |
| 51–65 | 39.4% | 42.7% | |
| >65 | 41.3% | 33.2%a | < 0.001 |
| Sex | |||
| Male | 46.0% | 44.8% | |
| Female | 54.0% | 55.2% | 0.32 |
| Body mass index | 31.17 | 29.73 | < 0.001 |
| ASA classification | |||
| 1 | 2.7% | 2.1% | |
| 2 | 47.8% | 74.9%a | |
| 3 | 47.9% | 22.8%a | |
| 4 | 1.8% | 0.2%a | < 0.001 |
| Levels fused | |||
| 1 | 76.1% | 82.9% | |
| 2 | 23.9% | 17.1% | < 0.001 |
Abbreviation: ASA, American Society of Anesthesiologists.