Brodke Darrel S, Gollogly Sohrab, Bachus Kent N, Alexander Mohr R, Nguyen Bao-Khang N
Department of Orthopaedics, University of Utah School of Medicine, Salt Lake City, 84132, USA.
Spine (Phila Pa 1976). 2003 Aug 15;28(16):1794-801. doi: 10.1097/01.BRS.0000083201.55495.0E.
An in vitro biomechanical study using a thoracolumbar corpectomy model to compare load sharing capabilities and stiffnesses of six different anterior instrumentation systems (three rod styles and three plate styles) for stabilizing the thoracic and lumbar spine.
To evaluate the axial load sharing capabilities of the instrumentation in a thoracolumbar corpectomy model and to measure the bending stiffness of the anterior instrumentation systems for the axes of flexion-extension, lateral bending, and axial rotation with and without an anterior column graft in place.
Prior publications have analyzed biomechanical characteristics of many spinal instrumentation systems. These reports have compared anterior instrumentation systems with posterior instrumentation systems, in situ fusion techniques, intervertebral spacers, structural allograft and instrumentation, and combined anterior and posterior instrumentation. Other reports have published data on the biomechanical characteristics of typical anterior and posterior spinal instrumentation systems. However, there are no published reports that specifically compare the characteristics of anterior plate-style with anterior rod-style systems, or examining load sharing capabilities.
Six constructs of each of six instrumentation systems were mounted on simulated vertebral bodies. A custom four-axis spine simulator was used to apply independent flexion-extension, lateral bending, and axial rotation moments as well as axial compressive loads. Axial load sharing was measured through a range of applied axial loads from 50 N to 500 N with rotational moments maintained at 0 Nm. The bending stiffness of each construct was calculated in response to +/-5.0 Nm moments about each axis of rotation with a 50 N compressive axial load with a full-length corpectomy graft in place, simulating reconstruction of the anterior column, and with no graft in place, simulating catastrophic graft failure. Statistical significance was determined using an analysis of variance and Fisher PLSD post hoc test with an alpha <or= 0.05.
Load sharing results ranged from 63% to 89%. There was an inverse relationship between load sharing and stiffness. No correlation was found between load sharing and implant style (rod vs. plate). With the graft in place, stiffness result varied by instrumentation system rather than by plate/rod style. Without the graft, the stiffness of the constructs decreased approximately one-third in flexion-extension, two-thirds in lateral bending, and one-fifth in axial rotation, underlying the importance of the graft in overall construct stiffness.
For both load sharing and stiffness, there is more influence from the design of the instrumentation system, than whether it is a plate or rod style system. The graft contributed to overall construct stiffness, particularly in lateral bending.
一项体外生物力学研究，使用胸腰椎椎体切除模型比较六种不同前路内固定系统（三种棒式和三种板式）稳定胸腰椎的负荷分担能力和刚度。
评估胸腰椎椎体切除模型中内固定器械的轴向负荷分担能力，并测量在有和无前路椎体间植骨的情况下，前路内固定系统在屈伸、侧方弯曲和轴向旋转轴向上的弯曲刚度。
既往文献分析了许多脊柱内固定系统的生物力学特性。这些报告比较了前路内固定系统与后路内固定系统、原位融合技术、椎间融合器、结构性同种异体骨与内固定以及前后联合内固定。其他报告公布了典型的脊柱前路和后路内固定系统的生物力学特性数据。然而，尚无专门比较前路板式与棒式系统特性或研究负荷分担能力的报告发表。
将六种内固定系统中的每一种构建六个试件，安装在模拟椎体上。使用定制的四轴脊柱模拟器施加独立的屈伸、侧方弯曲和轴向旋转力矩以及轴向压缩载荷。在旋转力矩保持为0 Nm的情况下，通过50 N至500 N的一系列轴向载荷测量轴向负荷分担情况。在有全长椎体切除植骨模拟前路椎体重建以及无植骨模拟灾难性植骨失败的情况下，对每个试件施加围绕每个旋转轴的±5.0 Nm力矩以及50 N的轴向压缩载荷，计算每个构建的弯曲刚度。使用方差分析和Fisher PLSD事后检验确定统计学显著性，α≤0.05。
负荷分担结果在63%至89%之间。负荷分担与刚度之间呈反比关系。未发现负荷分担与植入物类型（棒式与板式）之间存在相关性。有植骨时, 刚度结果因内固定系统而异，而非因板/棒类型而异。无植骨时，构建的刚度在屈伸时降低约三分之一，在侧方弯曲时降低三分之二，在轴向旋转时降低五分之一，这突出了植骨对整体构建刚度的重要性。
对于负荷分担和刚度而言，内固定系统的设计比其是板式还是棒式系统的影响更大。植骨有助于提高整体构建刚度，尤其是在侧方弯曲时。
