Disc Dynamics Inc., Eden Prairie, MN 55344, USA.
Spine (Phila Pa 1976). 2010 Jul 1;35(15):1445-53. doi: 10.1097/BRS.0b013e3181bef192.
A validated L3-L4 nonlinear finite element model was used to evaluate strain and pressure in the surrounding structures for 4 nucleus replacement technologies.
The objective of the current study was to compare subsidence and anular damage potential between 4 current nucleus replacement technologies. It was hypothesized that a fully conforming nucleus replacement would minimize the risk of both subsidence and anular damage.
Nucleus pulposus replacements are emerging as a less invasive alternative to total disc replacement and fusion as a solution to degenerative intervertebral discs. Multiple technologies have been developed and are currently undergoing clinical investigation.
The testing conditions were applied by excavating the nucleus of the intact model and virtually implanting models representing the various nucleus replacement technologies. The implants consisted of a conforming injectable polyurethane (E = 4 MPa), soft hydrogel (E = 4 MPa), stiff hydrogel (E = 20 MPa), and polyether-etherketone (PEEK) on PEEK articulating designs. The model was exercised in flexion, extension, lateral bending, axial rotation (7.5 Nm with 450 N preload), and compression (1000 N). Vertebral body strain, anular maximum shear strain, endplate contact pressure, anulus-implant contact pressure, and bone remodeling stimulus were reported.
The PEEK implant induced strain maxima in the vertebral bodies with associated endplate contact pressure concentrations. For the PEEK and hydrogel implants, areas of nonconformity with the endplate indicated adjacent bone resorption. Lack of conformity between the implant and inner anulus for the PEEK and hydrogel implants resulted in inward anular bulging with associated increased maximum shear strain. The conforming polyurethane implant maintained outward bulging of the inner anular wall and indicated no bone resorption or stress shielding adjacent to the implant.
A fully conforming nucleus replacement resulted in a decreased propensity for subsidence, anular bulging, and further degeneration of the anulus when compared with nonconforming implants.
使用经过验证的 L3-L4 非线性有限元模型，评估了 4 种核置换技术周围结构的应变和压力。
本研究的目的是比较 4 种当前核置换技术的沉降和环形损伤潜力。假设完全顺应的核置换术将最大限度地降低沉降和环形损伤的风险。
作为全椎间盘置换和融合术治疗退行性椎间盘疾病的替代方法，髓核置换术作为一种微创技术正在不断发展。已经开发出多种技术，并正在进行临床研究。
通过挖掘完整模型的核来施加测试条件，并通过虚拟植入代表各种核置换技术的模型来实现。植入物由顺应性可注射聚氨酯（E = 4 MPa）、软水凝胶（E = 4 MPa）、硬水凝胶（E = 20 MPa）和聚醚醚酮（PEEK）组成，PEEK 关节设计。模型在屈伸、侧屈、轴向旋转（7.5 Nm 预加载 450 N）和压缩（1000 N）下进行运动。报告了椎体应变、环形最大剪切应变、终板接触压力、环形-植入物接触压力和骨重塑刺激。
PEEK 植入物导致椎体应变最大值，并伴有终板接触压力集中。对于 PEEK 和水凝胶植入物，与终板不一致的区域表明相邻骨吸收。PEEK 和水凝胶植入物与内环形之间的不顺应性导致内环形隆起，伴有最大剪切应变增加。顺应性聚氨酯植入物保持了内环形壁的向外隆起，并且在植入物附近没有骨吸收或应力屏蔽。
与非顺应性植入物相比，完全顺应的核置换术降低了沉降、环形隆起和环形进一步退变的趋势。
