A range of same-sized screws are sterilized and shelved together for surgical procedures enabling rapid intra-operative selection based on need. Most screws are not used and sterilized multiple times before selection. The effect of multiple sterilizations on screw properties is currently unknown. The purpose of this study is to determine if repeated sterilization cycles affect the biomechanical properties of surgical screws used for orthopedic procedures. Our hypothesis is that repeated sterilizations will have a negative effect on the mechanical properties of surgical screws. Both 3.5 mm and 2.0 mm self-tapping, cortical screws underwent autoclave sterilization for 1, 50, or 100 cycles.After sterilization, screws were inserted into canine cadaver femurs and biomechanical properties were measured including peak insertional torque, torque to failure, and pullout strength. For 3.5 mm screws, there was a significant decrease in mean insertional torque between 1 and 50 sterilizations.The mean torque to failure for 3.5 mm screws was significantly decreased between 1 and both 50 and 100 sterilizations.For 2.0 mm screws, there was no significant difference in any tests. The results suggest that numerous sterilizations alter physical-mechanical properties of certain screw sizes. As only 3.5 mm screws were affected the changes may be more apparent in larger screws. The study was limited to 2.0 and 3.5 mm screws. Further testing is needed with different size screws to understand how to screw size affects results. There is evidence that numerous sterilizations produce altered physical-mechanical properties of certain screw sizes.
