Evaluation of the pullout strength of dual lead dual cored pedicle screw with cement augmentation

Pedicle screws are commonly used on the fixation of different spinal deformities. Pedicle screw loosening is a common problem for osteoporotic incidents. Cannulated screws with cement augmentation are widely used for that kind of cases. Dual lead dual cored (DLDC) pedicle screw was alternatively designed as a higher pullout providing device. It has already given promising pullout values without augmentation. However, DLDC had not been investigated with cement augmentation yet. This study concentrates on the usage of DLDC with cement augmentation as an alternative to cannulated screws with cement augmentation. Pullout tests for five groups were conducted on polyurethane foams (grade 20) and healthy bovine vertebrae. Normal and DLDC Screws were used both with and without cement. In addition, cannulated screws with cement augmentation were the fifth group of study. Test samples were prepared in accordance with surgical guidelines and ASTM F543 standard testing protocols. Pullout tests were conducted with Instron 3300 testing frame. Load versus displacement values were recorded and maximum pullout loads were stated. The DLDC pedicle screw with PMMA augmentation exhibited the highest pullout values. As expected normal pedicle screw without cement augmentation showed lowest pullout strength on both polyurethane foams and bovine vertebrae. Cement augmentated DLDC screws were exhibited nearly 40% higher pullout than cannulated screws. The DLDC pedicle screw with PMMA augmentation can be used for osteoporotic and/or severe osteoporotic patients according to its promising results on animal cadavers and synthetic foams.