Institute of Lightweight Design and Structural Biomechanics, Vienna University of Technology, Guhausstr. 27-29, A-1040 Vienna, Austria.
Bone. 2011 Jun 1;48(6):1370-7. doi: 10.1016/j.bone.2011.03.768. Epub 2011 Mar 29.
Tissue grafts are implanted in orthopedic surgery every day. In order to minimize infection risk, bone allografts are often delipidated with supercritical CO₂ and sterilized prior to implantation. This treatment may, however, impair the mechanical behavior of the bone graft tissue. The goal of this study was to determine clinically relevant mechanical properties of treated/sterilized human trabecular bone grafts, e.g. the apparent modulus, strength, and the ability to absorb energy during compaction. They were compared with results of identical experiments performed previously on untreated/fresh frozen human trabecular bone from the same anatomical site (Charlebois, 2008). We tested the hypothesis that the morphology-mechanical property relationships of treated cancellous allografts are similar to those of fresh untreated bone. The morphology of the allografts was determined by μCT. Subsequently, cylindrical samples were tested in unconfined and confined compression. To account for various morphologies, the experimental data was fitted to phenomenological mechanical models for elasticity, strength, and dissipated energy density based on bone volume fraction (BV/TV) and the fabric tensor determined by MIL. The treatment/sterilization process does not appear to influence bone graft stiffness. However, strength and energy dissipation of the bone grafts were found to be significantly reduced by 36% to 47% and 66% to 81%, respectively, for a broad range of volume fraction (0.14<BV/TV<0.39) and degree of anisotropy (1.24<DA<2.18). Since the latter properties are strongly dominated by BV/TV, the clinical consequences of this reduction can be compensated by using grafts with lower porosity. The data of this study suggests that an increase of 5-10% in BV/TV is sufficient to compensate for the reduced post-yield mechanical properties of treated/sterilized bone in monotonic compression. In applications where graft stiffness needs to be matched and strength is not a concern, treated allograft with the same BV/TV as an appropriate fresh bone graft may be used.
组织移植物每天都被用于骨科手术中。为了将感染风险降到最低，异体骨常采用超临界 CO₂ 脱脂并在植入前进行灭菌处理。然而，这种处理可能会损害移植物组织的机械性能。本研究的目的是确定经处理/灭菌的人松质骨移植物的临床相关机械性能，例如表观模量、强度和在压实过程中吸收能量的能力。这些性能与之前在同一解剖部位相同的未经处理/新鲜冷冻的人松质骨上进行的相同实验的结果进行了比较（Charlebois，2008）。我们测试了一个假设，即处理后的松质异体移植物的形态-机械性能关系与未经处理的新鲜骨相似。异体移植物的形态通过μCT 确定。随后，圆柱形样本在无约束和约束压缩下进行测试。为了考虑到各种形态，实验数据被拟合到基于骨体积分数（BV/TV）和通过 MIL 确定的织构张量的弹性、强度和耗散能量密度的经验力学模型。处理/灭菌过程似乎不会影响移植物的刚度。然而，发现骨移植物的强度和能量耗散分别降低了 36%至 47%和 66%至 81%，这是由于体积分数（0.14<BV/TV<0.39）和各向异性程度（1.24<DA<2.18）的广泛变化。由于后两个特性主要受 BV/TV 支配，因此可以通过使用具有较低孔隙率的移植物来补偿这种减少的临床后果。本研究的数据表明，在单调压缩中，BV/TV 增加 5-10%足以补偿经处理/灭菌的骨的屈服后机械性能降低。在需要匹配移植物刚度且强度不是问题的应用中，可以使用具有与适当新鲜骨移植物相同 BV/TV 的处理异体移植物。
