Department of Orthopedics, Shuang Ho Hospital, Taipei Medical University, New Taipei City 23561, Taiwan.
Department of Orthopaedics, School of Medicine, College of Medicine, Taipei Medical University, Taipei 110, Taiwan.
Medicina (Kaunas). 2022 Jun 15;58(6):808. doi: 10.3390/medicina58060808.
Background and Objectives: Using an appropriate torque to tighten set screws ensures the long-term stability of spinal posterior fixation devices. However, the recommended torque often varies between different devices and some devices do not state a recommended torque level. The purpose of this study is to evaluate the effect of set screw torque on the overall construct stability and fatigue life. Materials and Methods: Two commercial pedicle screw systems with different designs for the contact interface between the set screw and rod (Group A: plane contact, Group B: line contact) were assembled using torque wrenches provided with the devices to insert the set screws and tighten to the device specifications. The axial gipping capacity and dynamic mechanical stability of each bilateral construct were assessed in accordance with ASTM F1798 and ASTM F1717. Results: Increasing or decreasing the torque on the set screw by 1 Nm from the recommended level did not have a significant effect on the axial gripping capacity or fatigue strength of Group A (p > 0.05). For Group B, over-tightening the set screw by 1 Nm did cause a significant reduction in the fatigue strength. Conclusions: Excessive torque can damage the rod surface and cause premature failure. When insertion using a manual driver is preferred, a plane contact interface between the set screw and rod can reduce damage to the rod surface when the set screw is over-torqued.
使用适当的扭矩紧固螺丝可确保脊柱后路固定装置的长期稳定性。然而，不同的装置所推荐的扭矩值往往不同，有些装置则未说明推荐的扭矩值。本研究旨在评估螺丝扭矩对整体结构稳定性和疲劳寿命的影响。
使用装置随附的扭矩扳手将两组具有不同螺丝与杆接触面设计的商业椎弓根螺钉系统（组 A：平面接触，组 B：线接触）组装起来，并将螺丝拧至装置规格要求的扭矩。根据 ASTM F1798 和 ASTM F1717，评估每个双侧结构的轴向夹持能力和动态力学稳定性。
与推荐扭矩相比，将组 A 螺丝的扭矩增加或减少 1 Nm 对轴向夹持能力或疲劳强度没有显著影响（p>0.05）。对于组 B，螺丝扭矩超过 1 Nm 会显著降低疲劳强度。
过度扭矩会损坏杆表面并导致早期失效。当优先使用手动驱动器进行插入时，螺丝与杆之间的平面接触界面可减少螺丝过度拧紧时对杆表面的损坏。
