Introduction:
Pedicle screw loosening and failure pose challenges in spinal surgery, especially for patients with poor bone quality due to osteopenia or osteoporosis. As the aging population grows, these issues are increasingly common, yet there is no consensus on the optimal screw design. Cement augmentation improves screw stability but introduces local and systemic risks. This study investigates the biomechanical differences between single-threaded and double-threaded pedicle screws without cement augmentation to evaluate their effectiveness in compromised bone.
Methods:
This experimental study compared two polyaxial pedicle screw types—single-threaded (Group ST) and double-threaded (Group DT)—using sawbone models to simulate normal (n=12), osteopenic (n=12), and osteoporotic (n=12) bone. Screw dimensions were standardized (length: 45 mm, diameter: 6.5 mm), and pullout strength was assessed according to ASTM-F543 standards.
Results:
In normal bone, pullout strength differences between groups were not statistically significant (Group ST: 2271 ± 197N, Group DT: 2196 ± 178N, p=0.5). However, in osteopenic bone, double-threaded screws showed significantly higher pullout strength than single-threaded screws (Group DT: 631 ± 17N vs. Group ST: 600 ± 23N, p=0.02). In osteoporotic bone, double-threaded screws also demonstrated superior holding power with a 180° rotation before failure (p=0.0163).
Conclusion:
Double-threaded pedicle screws appear to offer enhanced pullout and holding strength in osteopenic and osteoporotic bone, suggesting an advantage in spinal stabilization for patients with compromised bone quality. These screws may serve as an effective alternative to cement augmentation, potentially improving patient safety and stabilization outcomes. Further studies are needed to confirm these findings and support clinical application.
no