Turkish Neurosurgery
How to Reduce Stress on the Pedicle Screws In Thoracic Spine? Importance of Screw Trajectory: A Finite Element Analysis
Yahya Güvenç1, Göktuğ Akyoldaş2, Salim Şentürk2, Deniz Erbulut3, Onur Yaman2, Ali Fahir Özer2
1Marmara University, Neurosurgery, Istanbul,
2Koç University Hospital, Neurosurgery, Istanbul,
3Medipol University , Biomedical Engineering, Istanbul,
DOI: 10.5137/1019-5149.JTN.21895-17.2

Aim:With wide application of the pedicle screw, clinical concerns have focused on accurate placement of the screws. Anatomic trajectory (AT) and straightforward trajectory (ST) are two popular techniques of pedicle screw insertion. Herein, we investigated the biomechanical comparison of thoracic transpedicular screw trajectories on the sagittal plane. To the best of our knowledge, this is the first comparative finite element analysis (FEA) on the different insertion trajectories of the pedicle screws in the thoracic spine.Material and Methods:A three-dimensional, nonlinear FEA model of T8 through T9 was used. AT and ST models of the transpedicular screws were used in the intact FEA model. The von-Mises stress and range of motion (ROM) of the transpedicular screws were evaluated.Results:The difference in ROM between both techniques was negligible. In lateral bending and axial rotation, FEA showed decrease in stress by 25% and 8%, respectively, when pedicle screws were placed using AT.Conclusion:AT decreased the von-Mises stress of the pedicle screws, thereby reducing the rates of screw breakage and fatigue risks. In addition, we believe that AT could protect against screw loosening because the von-Mises stress of the internal fixation was scattered.

Corresponding author : Yahya Güvenç