Charité - Universitätsmedizin Berlin, Julius Wolff Institut, Berlin, Germany.
Med Eng Phys. 2009 Dec;31(10):1307-12. doi: 10.1016/j.medengphy.2009.08.013. Epub 2009 Sep 19.
Large implants for vertebral body replacement (VBR) have a large footprint, and are normally supported by stronger bone at the rim of the vertebral body. But they also necessitate a greater corpectomy defect in the vertebral body concerned. In order to study the effect of implant size on contact pressure on the adjacent vertebral bodies and thus the risk of implant subsidence, an osseoligamentous finite element model of the lumbar spine was employed. The VBR was inserted at the level of L4 and additionally stabilized by posterior spinal instrumentation. Flat and curved vertebral endplates, small and large corpectomy defects, different implant positions and axial preloads as well as normal and osteoporotic vertebral bodies were simulated. Contact pressures in the vertebral body are increased for a curved vertebral endplate in comparison with a flat one, they are increased when an additional implant preload was assumed, and they are usually decreased for an osteoporotic vertebra when compared to a non-osteoporotic one. In some cases the average contact pressures were higher for the small-sized VBR, in others for the large-sized one. Our results reveal that from the mechanical point of view, a small-sized VBR is not generally disadvantageous.
大尺寸的椎体置换植入物（VBR）具有较大的接触面，通常由椎体边缘较坚固的骨骼支撑。但它们也需要在相关的椎体上进行更大的椎体切除术缺损。为了研究植入物尺寸对相邻椎体接触压力的影响，从而研究植入物下沉的风险，采用了腰椎的骨韧带有限元模型。在 L4 水平插入 VBR，并通过后路脊柱器械进行额外的稳定。模拟了平坦和弯曲的椎体终板、小和大的椎体切除术缺损、不同的植入物位置和轴向预加载以及正常和骨质疏松的椎体。与平坦的椎体终板相比，弯曲的椎体终板会增加椎体的接触压力；当假设额外的植入物预加载时，接触压力会增加；与非骨质疏松椎体相比，骨质疏松椎体的接触压力通常会降低。在某些情况下，小尺寸的 VBR 的平均接触压力较高，而在其他情况下，大尺寸的 VBR 的平均接触压力较高。我们的结果表明，从力学角度来看，小尺寸的 VBR 通常没有不利之处。
