Ferguson Stephen J, Visser Judith M A, Polikeit Anne
Institute for Surgical Technology and Biomechanics, MEM Research Center, University of Berne, Stauffacherstrasse 78, 3014 Bern, Switzerland.
Eur Spine J. 2006 Feb;15(2):149-56. doi: 10.1007/s00586-005-0915-5. Epub 2005 Jun 7.
Polyetheretherketone (PEEK) is a novel polymer with potential advantages for its use in demanding orthopaedic applications (e.g. intervertebral cages). However, the influence of a physiological environment on the mechanical stability of PEEK has not been reported. Furthermore, the suitability of the polymer for use in highly stressed spinal implants such as intervertebral cages has not been investigated. Therefore, a combined experimental and analytical study was performed to address these open questions. A quasi-static mechanical compression test was performed to compare the initial mechanical properties of PEEK-OPTIMA polymer in a dry, room-temperature and in an aqueous, 37 degrees C environment (n=10 per group). The creep behaviour of cylindrical PEEK polymer specimens (n=6) was measured in a simulated physiological environment at an applied stress level of 10 MPa for a loading duration of 2000 hours (12 weeks). To compare the biomechanical performance of different intervertebral cage types made from PEEK and titanium under complex loading conditions, a three-dimensional finite element model of a functional spinal unit was created. The elastic modulus of PEEK polymer specimens in a physiological environment was 1.8% lower than that of specimens tested at dry, room temperature conditions (P<0.001). The results from the creep test showed an average creep strain of less than 0.1% after 2000 hours of loading. The finite element analysis demonstrated high strain and stress concentrations at the bone/implant interface, emphasizing the importance of cage geometry for load distribution. The stress and strain maxima in the implants were well below the material strength limits of PEEK. In summary, the experimental results verified the mechanical stability of the PEEK-OPTIMA polymer in a simulated physiological environment, and over extended loading periods. Finite element analysis supported the use of PEEK-OPTIMA for load-bearing intervertebral implants.
聚醚醚酮（PEEK）是一种新型聚合物，在要求苛刻的骨科应用（如椎间融合器）中具有潜在优势。然而，生理环境对PEEK机械稳定性的影响尚未见报道。此外，该聚合物在高应力脊柱植入物（如椎间融合器）中的适用性也未得到研究。因此，开展了一项实验与分析相结合的研究来解决这些悬而未决的问题。进行了准静态机械压缩试验，以比较PEEK-OPTIMA聚合物在干燥的室温环境和37℃含水环境中的初始机械性能（每组n = 10）。在模拟生理环境中，对圆柱形PEEK聚合物试样（n = 6）施加10 MPa的应力水平，加载持续时间为2000小时（12周），测量其蠕变行为。为了比较由PEEK和钛制成的不同类型椎间融合器在复杂加载条件下的生物力学性能，建立了一个功能性脊柱单元的三维有限元模型。PEEK聚合物试样在生理环境中的弹性模量比在干燥的室温条件下测试的试样低1.8%（P<0.001）。蠕变试验结果表明，加载2000小时后平均蠕变应变小于0.1%。有限元分析表明，骨/植入物界面处存在高应变和应力集中，强调了融合器几何形状对载荷分布的重要性。植入物中的应力和应变最大值远低于PEEK的材料强度极限。总之，实验结果验证了PEEK-OPTIMA聚合物在模拟生理环境中以及在延长加载期内的机械稳定性。有限元分析支持将PEEK-OPTIMA用于承重椎间植入物。
