• Qiang Li, Hu Zhao, Jinshuai Yang, Shihong Song, and Xuyan Liu.
• School of Mechanical Engineering, University of Shanghai for Science and Technology, Shanghai, People's Republic of China; Shanghai Engineering Research Center of High-Performance Medical Device Materials, Shanghai, People's Republic of China. Electronic address: jxli@tju.edu.cn.
• World Neurosurg. 2024 Mar 1; 183: e345e354e345-e354.

ObjectiveTo improve implant stability parameters, including pedicle screw (PS) outer diameter, thread depth, and pitch, by finite element analysis.MethodsInsertion and pullout of the PS were simulated by finite element analysis, and the precision of simulation was evaluated by comparison with mechanical tests. Influences of the parameters on the maximum insertion torque and maximum pullout force were analyzed by computational simulations, including single-factor analysis and orthogonal experiments.ResultsThe simulation results agreed with the mechanical test results. The order of parameters influencing insertion torque and pullout force was outer diameter > pitch > thread depth. When the pilot hole diameter is 0.1 mm larger than the inner diameter of the PS, the calculated Pearson correlation coefficient between the maximum insertion torque and maximum pullout force was r = 0.99. The optimized PS had a maximum insertion torque of 485.16 N·mm and a maximum pullout force of 1726.33 N, 23.9% and 9.1% higher, respectively, than the values of standard screws.ConclusionsThe presently used models are feasible for evaluating the implant stability of PSs. The maximum insertion torque and maximum pullout force of PSs are highly correlated and can be improved by increasing the outer diameter and decreasing pitch. Although with the parameters of the PS, pedicle size and bone mineral density are 2 additional factors to consider for better implant stability.Copyright © 2023 Elsevier Inc. All rights reserved.

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