Engineering Center for Orthopedic Research Excellence (E-CORE), Departments of Bioengineering and Orthopaedic Surgery, University of Toledo, Toledo, OH, USA.
Spine & Scoliosis Specialists, Tampa, FL, USA.
Eur Spine J. 2022 Nov;31(11):3050-3059. doi: 10.1007/s00586-022-07331-7. Epub 2022 Aug 6.
Multi-rod constructs are used commonly to stabilize pedicle subtraction osteotomies (PSO). This study aimed to evaluate biomechanical properties of different satellite rod configurations and effects of screw-type spanning a PSO.
A validated 3D spinopelvic finite element model with a L3 PSO (30°) was used to evaluate 5 models: (1) Control (T10-pelvis + 2 rods); (2) lateral satellite rods connected via offsets to monoaxial screws (LatSat-Mono) or (3) polyaxial screws (LatSat-Poly); (4) in-line satellite rods connected to monoaxial screws (InSat-Mono) or (4) polyaxial screws (InSat-Poly). Global and PSO range of motions (ROM) were recorded. Rods' von Mises stresses and PSO forces were recorded and the percent differences from Control were calculated.
All satellite rods (save InSat-Mono) increased PSO ROM and decreased primary rods' von Mises stresses at the PSO. Lateral rods increased PSO forces (LatSat-Mono:347.1 N; LatSat-Poly:348.6 N; Control:336 N) and had relatively lower stresses, while in-line rods decreased PSO forces (InSat-Mono:280.1 N; InSat-Poly:330.7 N) and had relatively higher stresses. Relative to polyaxial screws, monoaxial screws further decreased PSO ROM, increased satellite rods' stresses, and decreased PSO forces for in-line rods, but did not change PSO forces for lateral rods.
Multi-rod constructs using in-line and lateral satellite rods across a PSO reduced primary rods' stresses. Subtle differences in biomechanics suggest lateral satellite rods, irrespective of screw type, increase PSO forces and lower rod stresses compared to in-line satellite rods, which had a high degree of posterior instrumentation stress shielding and lower PSO forces. Clinical studies are warranted to determine if these findings influence clinical outcomes.
多棒结构常用于稳定椎弓根切除截骨术（PSO）。本研究旨在评估不同卫星棒构型的生物力学特性以及螺钉跨越 PSO 的影响。
使用经过验证的具有 L3 PSO（30°）的 3D 脊柱骨盆有限元模型来评估 5 种模型：（1）对照（T10-骨盆+2 根棒）；（2）通过偏移连接到单轴螺钉的侧卫星棒（LatSat-Mono）或（3）多轴螺钉（LatSat-Poly）；（4）连接到单轴螺钉的直线卫星棒（InSat-Mono）或（4）多轴螺钉（InSat-Poly）。记录整体和 PSO 活动范围（ROM）。记录棒的 von Mises 应力和 PSO 力，并计算与对照相比的百分比差异。
所有卫星棒（除了 InSat-Mono）均增加了 PSO ROM，并降低了 PSO 处主要棒的 von Mises 应力。侧棒增加了 PSO 力（LatSat-Mono：347.1 N；LatSat-Poly：348.6 N；对照：336 N），且具有相对较低的应力，而直线棒则降低了 PSO 力（InSat-Mono：280.1 N；InSat-Poly：330.7 N），且具有相对较高的应力。与多轴螺钉相比，单轴螺钉进一步降低了 PSO ROM，增加了卫星棒的应力，并降低了直线棒的 PSO 力，但并未改变侧棒的 PSO 力。
使用侧卫星棒和直线卫星棒跨越 PSO 的多棒结构降低了主要棒的应力。生物力学方面的细微差异表明，侧卫星棒（无论螺钉类型如何）均比直线卫星棒增加了 PSO 力并降低了棒的应力，而直线卫星棒具有高度的后向器械应力屏蔽作用和较低的 PSO 力。需要进行临床研究以确定这些发现是否会影响临床结果。
