Schileo Enrico, Taddei Fulvia, Malandrino Andrea, Cristofolini Luca, Viceconti Marco
Laboratorio di Tecnologia Medica, Istituti Ortopedici Rizzoli, Via di Barbiano 1/10, 40136 Bologna, Italy.
J Biomech. 2007;40(13):2982-9. doi: 10.1016/j.jbiomech.2007.02.010. Epub 2007 Apr 16.
The prediction of the stress-state and fracture risk induced in bones by various loading conditions in individual patients using subject-specific finite element models still represents a challenge in orthopaedic biomechanics. The accuracy of the strain predictions reported in the literature is variable and generally not satisfactory. The aim of the present study was to evaluate if a proper choice of the density-elasticity relationship can lead to accurate strain predictions in the frame of an automatic subject-specific model generation strategy. To this aim, a combined numerical-experimental study was performed comparing finite element predicted strains with strain-gauges measurements obtained on eight cadaver proximal femurs, each instrumented with 15 rosettes mostly concentrated in the bone metaphyses, tested non-destructively in vitro under six different loading scenarios. Three different density-elasticity power relationships were selected from the literature and implemented in the finite element models derived from computed tomography data. The results of the present study confirm the great influence of the density-elasticity relationship used on the accuracy of numerical predictions. One of the tested constitutive laws provided a very good agreement (R(2)=0.91, RMSE lower than 10% of the maximum measured value) between numerical calculations and experimental measurements. The presented results show, in addition, that the adoption of a single density-elasticity relationship over the whole bone density range is adequate to obtain an accuracy that is already suitable for many applications.
使用个体化有限元模型预测个体患者在各种负荷条件下骨骼中产生的应力状态和骨折风险，在骨科生物力学领域仍然是一项挑战。文献中报道的应变预测准确性参差不齐，总体上并不令人满意。本研究的目的是评估在自动生成个体化模型策略的框架内，适当选择密度 - 弹性关系是否能得出准确的应变预测结果。为此，开展了一项数值与实验相结合的研究，将有限元预测应变与在八个尸体近端股骨上获得的应变片测量结果进行比较，每个股骨都安装了15个应变片，大多集中在骨干部位，在体外六种不同负荷情况下进行无损测试。从文献中选取三种不同的密度 - 弹性幂关系，并应用于从计算机断层扫描数据导出的有限元模型中。本研究结果证实了所使用的密度 - 弹性关系对数值预测准确性有很大影响。其中一个测试的本构定律在数值计算和实验测量之间提供了非常好的一致性（R(2)=0.91，均方根误差低于最大测量值的10%）。此外，所呈现的结果表明，在整个骨密度范围内采用单一的密度 - 弹性关系足以获得适用于许多应用的准确性。
