Van Rietbergen B, Huiskes R, Eckstein F, Rüegsegger P
Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands.
J Bone Miner Res. 2003 Oct;18(10):1781-8. doi: 10.1359/jbmr.2003.18.10.1781.
Quantitative information about bone tissue-level loading is essential for understanding bone mechanical behavior. We made microfinite element models of a healthy and osteoporotic human femur and found that tissue-level strains in the osteoporotic femoral head were 70% higher on average and less uniformly distributed than those in the healthy one.
Bone tissue stresses and strains in healthy load-adapted trabecular architectures should be distributed rather evenly, because no bone tissue is expected to be overloaded or unused. In this study, we evaluate this paradigm with the use of microfinite element (microFE) analyses to calculate tissue-level stresses and strains for the human femur. Our objectives were to quantify the strain distribution in the healthy femur, to investigate to what extent this distribution is affected by osteoporosis, to determine if osteoporotic bone is simply bone adapted to lower load levels, and to determine the "safety factor" for trabecular bone.
microFE models of a healthy and osteoporotic proximal femur were made from microcomputed tomography images. The models consisted of over 96 and 71 million elements for the healthy and osteoporotic femur, respectively, and represented their internal and external morphology in detail. Stresses and strains were calculated for each element and their distributions were calculated for a volume of interest (VOI) of trabecular bone in the femoral head.
The average tissue-level principal strain magnitude in the healthy VOI was 304 +/- 185 microstrains and that in the osteoporotic VOI was 520 +/- 355 microstrains. Calculated safety factors were 8.6 for the healthy and 4.9 for the osteoporotic femurs. After reducing the force applied to the osteoporotic model to 59%, the average strain compared with that of the healthy femur, but the SD was larger (208 microstrains).
Strain magnitudes in the osteoporotic bone were much higher and less uniformly distributed than those in the healthy one. After simulated joint-load reduction, strain magnitudes in the osteoporotic femur were very similar to those in the healthy one, but their distribution is still wider and thus less favorable.
关于骨组织水平负荷的定量信息对于理解骨的力学行为至关重要。我们建立了健康和骨质疏松人类股骨的微观有限元模型，发现骨质疏松股骨头的组织水平应变平均比健康股骨头高70%，且分布更不均匀。
在健康的适应负荷的小梁结构中，骨组织应力和应变应相当均匀地分布，因为预计没有骨组织会过载或未被使用。在本研究中，我们使用微观有限元（microFE）分析来评估这一范式，以计算人类股骨的组织水平应力和应变。我们的目标是量化健康股骨中的应变分布，研究这种分布受骨质疏松影响的程度，确定骨质疏松骨是否只是适应较低负荷水平的骨，并确定小梁骨的“安全系数”。
从微观计算机断层扫描图像建立健康和骨质疏松近端股骨的microFE模型。健康股骨和骨质疏松股骨的模型分别由超过9600万个和7100万个单元组成，并详细呈现了它们的内部和外部形态。计算每个单元的应力和应变，并计算股骨头小梁骨感兴趣体积（VOI）内的应力和应变分布。
健康VOI中的平均组织水平主应变大小为304±185微应变，骨质疏松VOI中的为520±355微应变。计算得到的健康股骨安全系数为8.6，骨质疏松股骨为4.9。将施加到骨质疏松模型的力降低到59%后，平均应变与健康股骨相比，但标准差更大（208微应变）。
骨质疏松骨中的应变大小比健康骨高得多且分布更不均匀。模拟关节负荷降低后，骨质疏松股骨中的应变大小与健康股骨非常相似，但其分布仍然更宽，因此更不理想。
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