Bellini Chiara Maria, Galbusera Fabio, Raimondi Manuela T, Mineo Giuseppe V, Brayda-Bruno Marco
Bioengineering Unit, IRCCS Istituto Ortopedico Galeazzi, Milan, Italy.
J Spinal Disord Tech. 2007 Aug;20(6):423-9. doi: 10.1097/bsd.0b013e318031af6f.
Target of the study was to predict the biomechanics of the instrumented and adjacent levels due to the insertion of the DIAM spinal stabilization system (Medtronic Ltd). For this purpose, a 3-dimensional finite element model of the intact L3/S1 segment was developed and subjected to different loading conditions (flexion, extension, lateral bending, axial rotation). The model was then instrumented at the L4/L5 level and the same loading conditions were reapplied. Within the assumptions of our model, the simulation results suggested that the implant caused a reduction in range of motion of the instrumented level by 17% in flexion and by 43% in extension, whereas at the adjacent levels, no significant changes were predicted. Numerical results in terms of intradiscal pressure, relative to the intact condition, predicted that the intervertebral disc at the instrumented level was unloaded by 27% in flexion, by 51% in extension, and by 6% in axial rotation, while no variations in pressure were caused by the device in lateral bending. At the adjacent levels, a change of relative intradiscal pressure was predicted in extension, both at the L3/L4 level, which resulted unloaded by 26% and at the L5/S1 level, unloaded by 8%. Furthermore, a reduction in terms of principal compressive stress in the annulus fibrosus of the L4/L5 instrumented level was predicted, as compared with the intact condition. These numerical predictions have to be regarded as a theoretical representation of the behavior of the spine, because any finite element model represents only a simplification of the real structure.
本研究的目标是预测由于植入DIAM脊柱稳定系统（美敦力有限公司）而导致的植入节段及相邻节段的生物力学情况。为此，建立了完整L3/S1节段的三维有限元模型，并使其承受不同的载荷条件（前屈、后伸、侧弯、轴向旋转）。然后在L4/L5节段植入该模型，并重新施加相同的载荷条件。在我们模型的假设范围内，模拟结果表明，植入物使植入节段在前屈时的活动范围减少了17%，在后伸时减少了43%，而在相邻节段，预计不会有显著变化。相对于完整状态，关于椎间盘内压力的数值结果预测，植入节段的椎间盘在前屈时卸载了27%，后伸时卸载了51%，轴向旋转时卸载了6%，而在侧弯时该装置未引起压力变化。在相邻节段，预计在后伸时L3/L4节段和L5/S1节段的椎间盘内相对压力会发生变化，L3/L4节段卸载了26%，L5/S1节段卸载了8%。此外，与完整状态相比，预计L4/L5植入节段的纤维环主压应力会降低。这些数值预测应被视为脊柱行为的理论表现，因为任何有限元模型都只是真实结构的简化。
