Crawford R Paul, Rosenberg William S, Keaveny Tony M
Department of Neurological Surgery, University of California, San Francisco, CA 94143, USA.
J Biomech Eng. 2003 Aug;125(4):434-8. doi: 10.1115/1.1589772.
This study investigated the numerical convergence characteristics of specimen-specific "voxel-based" finite element models of 14 excised human cadaveric lumbar vertebral bodies (age: 37-87; M = 6, F = 8) that were generated automatically from clinical-type CT scans. With eventual clinical applications in mind, the ability of the model stiffness to predict the experimentally measured compressive fracture strength of the vertebral bodies was also assessed. The stiffness of "low"-resolution models (3 x 3 x 3 mm element size) was on average only 4% greater (p = 0.03) than for "high"-resolution models (1 x 1 x 1.5 mm) despite interspecimen variations that varied over four-fold. Damage predictions using low- vs high-resolution models were significantly different (p = 0.01) at loads corresponding to an overall strain of 0.5%. Both the high (r2 = 0.94) and low (r2 = 0.92) resolution model stiffness values were highly correlated with the experimentally measured ultimate strength values. Because vertebral stiffness variations in the population are much greater than those that arise from differences in voxel size, these results indicate that imaging resolution is not critical in cross-sectional studies of this parameter. However, longitudinal studies that seek to track more subtle changes in stiffness over time should account for the small but highly significant effects of voxel size. These results also demonstrate that an automated voxel-based finite element modeling technique may provide an excellent noninvasive assessment of vertebral strength.
本研究调查了14个切除的人类尸体腰椎椎体（年龄：37 - 87岁；男性6例，女性8例）基于体素的特定标本有限元模型的数值收敛特性，这些模型由临床类型的CT扫描自动生成。考虑到最终的临床应用，还评估了模型刚度预测椎体实验测量抗压骨折强度的能力。尽管标本间的变化幅度超过四倍，但“低”分辨率模型（单元尺寸为3×3×3毫米）的刚度平均仅比“高”分辨率模型（1×1×1.5毫米）大4%（p = 0.03）。在对应于总应变0.5%的载荷下，使用低分辨率与高分辨率模型的损伤预测存在显著差异（p = 0.01）。高分辨率（r2 = 0.94）和低分辨率（r2 = 0.92）模型的刚度值均与实验测量的极限强度值高度相关。由于人群中椎体刚度的变化远大于体素大小差异引起的变化，这些结果表明，在该参数的横断面研究中，成像分辨率并非关键因素。然而，旨在追踪随时间变化的更细微刚度变化的纵向研究应考虑体素大小的微小但高度显著的影响。这些结果还表明，基于体素的自动有限元建模技术可能为椎体强度提供出色的无创评估。
