Pitzen T, Geisler F H, Matthis D, Müller-Storz H, Pedersen K, Steudel W I
Department of Neurosurgery, Saarland University Hospital, 66421 Homburg, Germany.
Eur Spine J. 2001 Feb;10(1):23-9. doi: 10.1007/s005860000223.
The aim of the current study is twofold: first, to compare load sharing in compression between an intact and a surgically repaired lumbar spine motion segment L3/4 using a biomechanically validated finite element approach; second, to analyse the influence of bone mineral density on load sharing. Six cadaveric human lumbar spine segments (three segments L2/3 and three segments L4/5) were taken from fresh human cadavers. The intact segments were tested under axial compression of 600 N, first without preload and then following instrumented stabilisation. These results were compared to a finite element model simulating the effect of identical force on the intact segments and the segments with constructs. The predictions of both the intact and the surgically altered finite element model were always within one standard deviation of the mean stiffness as analysed by the biomechanical study. Thus, the finite element model was used to analyse load sharing under compression in an intact and a surgically repaired human lumbar spine segment model, using a variety of E moduli for cancellous bone of the vertebral bodies. In both the intact and the surgically altered model, 89% of the applied load passed through the vertebral bodies and the disc if an E modulus of 25 MPa was used for cancellous bone density. Using 10 MPa--representing soft, osteoporotic bone--this percentage decreased, but it increased using 100 MPa in both the intact and the altered segment. Thus, it is concluded that reconstruction of both the disc and the posterior elements with the implants used in the study recreates the ability of the spine to act as a load-sharing construction in compression. The similarity in load sharing between normal and instrumented spines appears to depend on assumed bone density, and it may also depend on applied load and loading history.
第一，使用经过生物力学验证的有限元方法，比较完整的和手术修复后的腰椎运动节段L3/4在压缩时的负荷分担情况；第二，分析骨密度对负荷分担的影响。从新鲜人体尸体上获取了六个尸体腰椎节段（三个L2/3节段和三个L4/5节段）。完整节段在600 N轴向压缩下进行测试，首先无预载，然后进行器械固定后测试。将这些结果与模拟相同力作用于完整节段和有植入物节段效果的有限元模型进行比较。生物力学研究分析表明，完整的和手术改变后的有限元模型的预测结果始终在平均刚度的一个标准差范围内。因此，使用有限元模型分析完整的和手术修复后的人体腰椎节段模型在压缩时的负荷分担情况，采用了多种椎体松质骨的弹性模量。在完整模型和手术改变后的模型中，如果将松质骨密度的弹性模量设为25 MPa，89%的外加负荷通过椎体和椎间盘。使用10 MPa（代表柔软的骨质疏松骨）时，这一百分比下降，但在完整节段和改变后的节段中使用100 MPa时，该百分比增加。因此，可以得出结论，使用本研究中所用的植入物对椎间盘和后部元件进行重建，可恢复脊柱在压缩时作为负荷分担结构的能力。正常脊柱和植入器械的脊柱在负荷分担上的相似性似乎取决于假定的骨密度，也可能取决于外加负荷和加载历史。
