Fusion surgery is usually a last resort to treat pain the patient is experiencing. Spine surgery poses several risks including infection, metallosis reaction, pseudoarthrosis (failure of a fusion), rod fracture, and pedicle screw loosening. The average cost of pseudarthrosis is reported to be $76,695 while an instrumentation failure has an average cost of $66,838. In spine surgery, pedicle screws are inserted into the pedicle from the dorsal aspect of the vertebrae, passing into the vertebral body. Currently pedicle screws are tested by measuring pullout strength (POS), or the tensile force required to pull the screw from the vertebrae. An increase in POS can be achieved by increasing the diameter of the screw, decreasing the tap size, increasing tapping insertional POS, and adjusting pedicle screw trajectory. Clinically, pedicle screw toggling (a moment or bending force applied to a fixed beam) is the physiological motion of the spine that could lead to pedicle screw loosening. There exists a need to understand how the screw acts on the bone to better understand failure. The average strain seen in extension and pullout for all specimens (n = 11) was 17.5E-6 and 8.16E-6 (p = 0.049) respectively. For flexion the average strain was 11.1E-6 and not significantly different from pullout (p > 0.05). Screws engaging cortical bone were plotted with a linear regression (R2 0.79) comparing pedicle to pedicle screw ratio and extension strains. This work showed the extension strains are significantly larger than pullout strains. Further tests should place strain gages around the bone and screw interface to better understand where strains should be measured. Also, for the most accurate comparison between all loading conditions, Rosette strain gages should be utilized.