Cloutier Luc P, Aubin Carl-Eric, Grimard Guy
Department of Mechanical Engineering, Ecole Polytechnique de Montréal, Canada Research Chair CAD Innovations in Orthopedic Engineering, Montreal, QC, Canada H3C 3A7.
Eur Spine J. 2007 Jul;16(7):1039-45. doi: 10.1007/s00586-006-0246-1. Epub 2007 Jan 5.
The biomechanical impact of the surgical instrumentation configuration for spine surgery is hard to evaluate by the surgeons in pre-operative situation. This study was performed to evaluate different configurations of the anterior instrumentation of the spine, with simulated post-operative conditions, to recommend configurations to the surgeons. Four biomechanical parameters of the anterior instrumentation with simulated post-operative conditions have been studied. They were the screw diameter (5.5-7.5 mm) and its angle (0 degrees - 22.5 degrees), the bone grip of the screw (mono-bi cortical) and the amount of instrumented levels (5-8). Eight configurations were tested using an experimental plan with instrumented synthetic spinal models. A follower load was applied and the models were loaded in flexion, torsion and lateral bending. At 5 Nm, average final stiffness was greater in flexion (0.92 Nm/degrees) than in lateral bending (0.56 Nm/degrees) and than in torsion (0.26 Nm/degrees). The screw angle was the parameter influencing the most the final stiffness and the coupling behaviors. It has a significant effect (p < or = 0.05) on increasing the final stiffness for a 22.5 degrees screw angle in flexion and for a coronal screw angle (0 degrees) in lateral bending. The bi-cortical bone grip of the screw significantly increased the initial stiffness in flexion and lateral bending. Mathematical models representing the behavior of an instrumented spinal model have been used to identify optimal instrumentation configurations. A variation of the angle of the screw from 22.5 degrees to 0 degrees gave a global final stiffness diminution of 13% and a global coupling diminution of 40%. The screw angle was the most important parameter affecting the stiffness and the coupling of the instrumented spine with simulated post-operative conditions. Information about the effect of four different biomechanical parameters will be helpful in preoperative situations to guide surgeons in their clinical choices.
脊柱手术中手术器械配置的生物力学影响在术前很难被外科医生评估。本研究旨在通过模拟术后情况来评估脊柱前路器械的不同配置，以便向外科医生推荐合适的配置。研究了模拟术后情况下前路器械的四个生物力学参数。它们是螺钉直径（5.5 - 7.5毫米）及其角度（0度 - 22.5度）、螺钉的骨质把持情况（单皮质 - 双皮质）以及固定节段数量（5 - 8个）。使用装有器械的合成脊柱模型的实验方案测试了八种配置。施加一个跟随载荷，并使模型进行前屈、扭转和侧弯加载。在5牛米的载荷下，平均最终刚度在前屈时（0.92牛米/度）大于侧弯时（0.56牛米/度）和扭转时（0.26牛米/度）。螺钉角度是对最终刚度和耦合行为影响最大的参数。对于前屈时22.5度的螺钉角度以及侧弯时冠状面螺钉角度（0度），它对增加最终刚度有显著影响（p≤0.05）。螺钉的双皮质骨质把持显著增加了前屈和侧弯时的初始刚度。已使用代表装有器械的脊柱模型行为的数学模型来确定最佳器械配置。螺钉角度从22.5度变化到0度会使整体最终刚度降低13%，整体耦合降低40%。在模拟术后情况下，螺钉角度是影响装有器械的脊柱刚度和耦合的最重要参数。有关四个不同生物力学参数影响的信息将有助于术前情况，指导外科医生做出临床选择。
