Lin Chia-Ying, Kang Heesuk, Rouleau Jeffrey P, Hollister Scott J, Marca Frank La
Spine Research Laboratory, Department of Neurosurgery, University of Michigan Medical School, Ann Arbor, MI 48109-2200, USA.
Spine (Phila Pa 1976). 2009 Jul 1;34(15):1554-60. doi: 10.1097/BRS.0b013e3181aa643b.
Segmental motion and bone-implant interface stresses were analyzed at C5-C6 levels with Bryan, Prestige LP, and ProDisc-C cervical disc prostheses using an image-based finite element modeling technique.
To predict stress patterns at the interface between prosthesis and lower vertebral end plate to better understand the underlying mechanisms of subsidence and how the load transfer pattern of each disc design affects segmental motion.
Subsidence is one of the most commonly reported device-related complications in intervertebral disc arthroplasty. Although clinical outcomes have been reported regarding many types of cervical prostheses, few reports have analyzed the effects of stress from cervical artificial discs to the vertebral end plate.
Three-dimensional voxel finite elements were built for C5-C6 spine unit based on computed tomography images acquired from a patient with indication for cervical disc arthroplasty. Models of facet joints and uncovertebral joints were added and artificial disc designs were placed in the intervertebral disc space. Static analyses were conducted under normal physiologic loads in flexion, extension, and lateral bending with precompression.
Bryan disc recovered highest range of motion (4.75 degrees ) due to the high elastic nucleus, and therefore imposed the lowest stresses superior to C6. The ProDisc-C and Prestige LP discs caused high stress concentrations around their central fins or teeth, and may initiate bone absorption. Analysis of Prestige LP disc may indicate possible subsidence posteriorly caused by the rear-positioned metal-to-metal joint.
Rigidity of the cores ("nuclei") in Prestige LP and ProDisc-C prostheses guarantee initial maintenance of disc height, but high contact stress takes place at the bone-end plate interface if they are improperly placed or undersized. Anchorage designs add an additional factor that may increase propensity of subsidence, indicated by the high contact stress occurring at the end plate flanges of Prestige LP, and at midline keel fixation on the end plate of ProDisc-C. Although Bryan disc differs in these 2 concerns, it also creates much larger displacement during motion with more variation in disc height that may theoretically increase the load sharing of facet and/or uncovertebral joints compared to more rigid artificial discs.
采用基于图像的有限元建模技术，分析了Bryan、Prestige LP和ProDisc-C颈椎间盘假体在C5-C6节段的节段运动和骨-植入物界面应力。
预测假体与下位椎体终板之间界面的应力模式，以更好地理解下沉的潜在机制，以及每种椎间盘设计的载荷传递模式如何影响节段运动。
下沉是椎间盘置换术中最常见的与器械相关的并发症之一。尽管已经报道了许多类型颈椎假体的临床结果，但很少有报告分析颈椎人工椎间盘应力对椎体终板的影响。
根据从一名有颈椎间盘置换术指征的患者获取的计算机断层扫描图像，构建C5-C6脊柱单元的三维体素有限元模型。添加了小关节和钩椎关节模型，并将人工椎间盘设计置于椎间盘间隙。在正常生理载荷下，进行前屈、后伸和侧屈并预压缩的静态分析。
由于高弹性髓核，Bryan椎间盘恢复了最高的活动度（4.75度），因此在C6上方施加的应力最低。ProDisc-C和Prestige LP椎间盘在其中心鳍或齿周围引起高应力集中，并可能引发骨吸收。对Prestige LP椎间盘的分析可能表明，后置金属对金属关节可能导致后方下沉。
Prestige LP和ProDisc-C假体的髓核刚度保证了椎间盘高度的初始维持，但如果放置不当或尺寸过小，骨-终板界面会出现高接触应力。锚固设计增加了一个可能增加下沉倾向的额外因素，Prestige LP终板凸缘处以及ProDisc-C终板中线龙骨固定处出现的高接触应力表明了这一点。尽管Bryan椎间盘在这两个问题上有所不同，但与更刚性的人工椎间盘相比，它在运动过程中也会产生更大的位移，椎间盘高度变化更大，理论上可能会增加小关节和/或钩椎关节的载荷分担。
