Effects of patient-related factors on screw loosening.
| Factor | Univariate | Multivariate | ||
| OR (95% CI) | P | OR (95% CI) | P | |
| Age (+1 y) | 0.99 (0.95–1.03) | 0.75 | - | |
| Gender (women) | 0.67 (0.16–2.73) | 0.58 | - | |
| Rheumatoid arthritis | 4.11e-08 (0.00–inf) | 0.99 | - | |
| Screw perforation (Grade 2 or 3) | 1.78e-07 (0.00–inf) | 0.99 | - | |
| Unilateral insertion | 8.50 (1.53–47.2) | 0.014 | 8.25 (1.49–45.8) | 0.015 |
Abbreviation: inf, infinity.