Multiple regression analysis of risk factors for surgical site infection.
| Risk Factor | OR | 95% CI | P Value |
| Body mass index | 1.114 | 1.020–1.217 | 0.016 |
| Skin to SP on x-ray imaging | 1.077 | 1.021–1.135 | 0.006 |
| Skin to SP on sagittal magnetic resonance imaging | 1.057 | 1.009–1.107 | 0.020 |
Abbreviations: SP, spinous process.