Results from multiple regression analyses
| Variables | Relative risk | 95% CI | p Value |
| Relative risk of OSF from a model including only significant predictors (excluding BSA, based on valves with complete serial numbers; n of OSF = 56) | |||
| Age at implantation (in years) | 0.96 | 0.94 to 0.98 | < 0.001 |
| Valve size | |||
| ⩽ 21 and 25 | 1.0 | – | 0.004 |
| 23 | 5.5 | 1.1 to 26.4 | |
| 27 | 4.2 | 0.8 to 20.1 | |
| 29 | 4.4 | 1.0 to 20.7 | |
| 31 | 8.5 | 1.9 to 37.4 | |
| 33 | 13.5 | 2.5 to 71.4 | |
| Shop order fracture rate | 1.4 | 1.2 to 1.5 | < 0.001 |
| Manufacturing date | |||
| Before 1981 | 1.0 | – | < 0.001 |
| 1981–1984 | 4.4 | 1.6 - 12.3 | |
| Relative risk of OSF from a model including only significant predictors (based on valves with complete serial numbers and known BSA; n of OSF = 34) | |||
| Age at implantation (in years) | 0.97 | 0.94 to 1.0 | 0.057 |
| BSA (0.5 m2) | 5.3 | 2.1 to 13.1 | < 0.001 |
| Valve size | 0.02 | ||
| ⩽ 21 and 25 | 1.0 | – | |
| 23 | 3.2 | 0.6 to 17.6 | |
| 27 | 2.6 | 0.5 to 14.5 | |
| 29 | 2.2 | 0.4 to 12.0 | |
| 31 | 6.4 | 1.4 to 29.6 | |
| 33 | 12.0 | 1.9 to 74.6 | |
| Shop order fracture rate | 1.4 | 1.2 to 1.6 | < 0.001 |
| Manufacturing date | |||
| Before 1981 | 1.00 | 0.006 | |
| 1981–1984 | 5.0 | 1.2 to 21.0 | |
BSA, body surface area.