Department of Mechanical Engineering, The University of Memphis, Memphis, TN 38152-3180, USA.
Med Eng Phys. 2010 Jul;32(6):595-603. doi: 10.1016/j.medengphy.2010.02.009. Epub 2010 Mar 7.
A detailed three-dimensional solid model of the full cervical spine (C1-C7 levels) and the finite element analysis method were used to investigate the extent of changes in various biomechanical properties brought about when surgical methods are used to treat condition(s) caused by or are a sequela of disc degeneration disease at the C5-C6 level. The surgical methods simulated were anterior cervical discectomy and fusion, with interbody fusion achieved using a notional brick-shaped graft only; anterior cervical discectomy alone; percutaneous nucleotomy; and three variants of nucleus replacement. The control case was a model of an intact, healthy, adult spine. Each of these seven models was subjected to (1) flexion moment, extension moment, left lateral bending moment, right lateral bending moment, clockwise-acting axial rotation moment, and counterclockwise-acting axial rotation moment, with a compression pre-load applied simultaneously with each of these loadings and (2) an axial compression force (applied as a uniform pressure) only. For each combination of model and applied loading, the maximum von Mises stress and the maximum strain energy density were determined for tissues at the treated level, at one level above the treated level, and at one level below the treated level and (2) the total principal rotation angles at each of the intersegmental positions of the entire model. In addition, for each of the study cases, we obtained the longitudinal displacement of each of the models when subjected to the axial compression force only. We found markedly fewer changes (relative to the results when the intact, healthy spine model was used) in each of the above-mentioned biomechanical parameters above a specified threshold in the case of the simulated percutaneous nucleotomy and simulated nucleus replacement models, on one hand, compared to the simulated fusion and simulated discectomy models, on the other. This finding is in consonance with the evolving clinical practice of using minimally invasive surgical methods for treating problem(s) such as soft cervical disc herniations.
采用详细的全颈椎（C1-C7 节段）三维实体模型和有限元分析方法，研究了 C5-C6 节段椎间盘退变性疾病所致或其后遗症的各种病变情况下，采用前路颈椎间盘切除融合术（采用概念性砖形移植物进行椎间融合）、单纯前路颈椎间盘切除术、经皮髓核切除术和三种核置换术治疗时，各种生物力学特性变化的程度。对照模型为完整健康成人脊柱模型。对这 7 种模型分别进行以下两种加载方式：（1）施加前屈力矩、伸展力矩、左侧弯力矩、右侧弯力矩、顺时针轴向旋转力矩和逆时针轴向旋转力矩，同时对每个模型施加压缩预载荷；（2）仅施加轴向压缩力（作为均匀压力施加）。对于每个模型和加载组合，确定治疗节段、治疗节段上方和下方的组织的最大 von Mises 应力和最大应变能密度，以及整个模型各个节段的总主旋转角度。此外，对于每个研究病例，我们仅在施加轴向压缩力的情况下，确定每个模型的纵向位移。与使用完整健康脊柱模型的结果相比，一方面，模拟经皮髓核切除术和模拟核置换术模型在特定阈值以上的上述生物力学参数变化明显少于模拟融合和模拟椎间盘切除术模型。这一发现与采用微创外科方法治疗软性颈椎间盘突出症等问题的不断发展的临床实践相一致。
