Influence of Lateral Perforation on the Biomechanical Stability of Thoracic Pedicle Screws

Study DesignExperimental ex vivo biomechanical cadaver study.ObjectivesThoracic pedicle screws are essential for stabilizing spinal injuries, but misplacement remains a frequent complication. While many studies focus on neurovascular injuries, the impact of the degree of lateral misplacement (offset) on the biomechanical stability of thoracic pedicle screws has not been examined. Therefore, this study aimed to evaluate the influence of lateral offset on pullout force (POF) and peak insertion torque (PIT), and to analyse additional factors such as screw diameter, screw length, and bone quality.MethodsIn this ex vivo cadaveric study, 61 thoracic vertebrae (T1-T12) from seven human cadavers were instrumented using pedicle screws placed with predefined lateral offsets via 3D-printed templates. Each vertebra received one optimal and one offset screw for pairwise comparison. Biomechanical testing included cyclic loading followed by axial pullout testing. Linear mixed-effects models assessed the influence of offset, screw diameter, screw length, and bone density on POF and PIT.ResultsLateral offset significantly reduced POF and PIT. Each millimeter of offset decreased POF by 41.1 N (-9.2%; p<0.001) and PIT by 0.079 Nm (-5.9%; p=0.002). Larger screw diameter significantly increased both POF and PIT (p=0.020; p<0.001). Screw length and bone quality showed no significant independent effects. POF and PIT were strongly correlated (r=0.637, p<0.001).ConclusionsLateral offset significantly reduced both pullout force and peak insertion torque of thoracic pedicle screws, demonstrating a progressive loss of biomechanical stability with increasing misplacement. These findings underline the biomechanical relevance of accurate thoracic pedicle screw placement.