Bivariate analysis of risk ratio for demographic and perioperative characteristics.
| Characteristic | Among Extended Length of Stays, % | Relative Risk | CI | P Valuea |
| Age | ||||
| <50 y | 42.3% | Reference | ||
| ≥50 y | 57.7% | 1.1 | (0.8–1.7) | 0.559 |
| Gender | ||||
| Women | 48.1% | Reference | ||
| Men | 51.9% | 1.0 | (0.7–1.5) | 0.845 |
| Body mass index | ||||
| <30 kg/m2 | 53.9% | Reference | ||
| ≥30 kg/m2 | 46.2% | 0.9 | (0.6–1.4) | 0.697 |
| Smoking status | ||||
| Nonsmoker | 84.6% | Reference | ||
| Smoker | 15.4% | 0.8 | (0.5–1.4) | 0.476 |
| American Society of Anesthesiologists score | ||||
| <2 | 71.2% | Reference | ||
| ≥2 | 28.9% | 1.7 | (1.2–2.4) | 0.003 |
| Charlson Comorbidity Index score | ||||
| <1 | 20.5% | Reference | ||
| ≥1 | 79.6% | 1.0 | (0.6–1.7) | 0.851 |
| Hypertension | ||||
| Nonhypertensive | 63.5% | Reference | ||
| Hypertensive | 36.5% | 1.4 | (1.0–2.1) | 0.066 |
| Diabetes | ||||
| Nondiabetic | 80.8% | Reference | ||
| Diabetic | 19.2% | 1.5 | (1.0–2.3) | 0.037 |
| Preoperative VAS backb | ||||
| <7 | - | - | - | - |
| ≥7 | - | - | - | - |
| Preoperative VAS leg | ||||
| <7 | 17.3% | Reference | ||
| ≥7 | 82.7% | 2.1 | (1.2–3.8) | 0.012 |
| Operative time | ||||
| ≤127 min | 44.2% | Reference | ||
| >127 min | 55.8% | 1.1 | (0.8–1.7) | 0.560 |
| Estimated blood loss | ||||
| ≤63 mL | 57.7% | Reference | ||
| >63 mL | 42.3% | 1.2 | (0.8–1.7) | 0.415 |