ARTORG Center for Biomedical Engineering Research, University of Bern, Bern, Switzerland.
ARTORG Center for Biomedical Engineering Research, University of Bern, Bern, Switzerland.
Bone. 2020 Dec;141:115575. doi: 10.1016/j.bone.2020.115575. Epub 2020 Aug 11.
Micro finite element analysis (μFE) is a widely applied tool in biomedical research for assessing in vivo mechanical properties of bone at measurement sites, including the ultra-distal radius and tibia. A finite element approach (hFE) based on homogenized constitutive models for trabecular bone offers an attractive alternative for clinical use, as it is computationally less expensive than traditional μFE. The respective patient-specific models for in vivo bone strength estimation are usually based on standard clinical high-resolution peripheral quantitative CT (HR-pQCT) measurements. They include a scan region of roughly 10 mm in height and are referred to as single-sections. It has been shown, that these small peripheral bone sections don't reliably cover the fracture line in Colles' fractures and therefore the weakest region at the radius. Recently introduced multiple section (multiple adjacent single-sections) measurements might improve the evaluation of bone strength, but little is known about the repeatability of hFE estimations in general, and especially for multiple section measurement protocols. Accordingly, the aim of the present work is to quantify repeatability of clinical in vivo bone strength measurement by hFE on multiple section HR-pQCT reconstructions at the distal radius and tibia.
Nineteen healthy Swiss women (43.6y ± 17.8y) and twenty men (48.2y ± 19.4y) were examined with HR-pQCT at 61 μm isotropic voxel resolution. Each subject was first scanned three times using a double-section (336 slices) at the distal radius and then three times using a triple-section (504 slices) at the distal tibia. The multiple section HR-pQCT reconstructions were graded for motion artefacts and non-linear hFE models (radius and tibia) and linear μFE models (only radius) were generated for estimation of stiffness and ultimate load. Then in vivo repeatability errors were computed in terms of root mean square coefficients of variation (CV).
In vivo repeatability errors of non-linear hFE stiffness (S) and ultimate load (F) were significantly higher at the radius (S: 2.71% and F: 2.97%) compared to the tibia (S: 1.21%, F: 1.45%). Multiple section linear μFE at the radius resulted in substantially higher repeatability errors (S: 5.38% and F: 10.80%) compared to hFE.
DISCUSSION/CONCLUSION: Repeatability errors of hFE outcomes based on multiple section measurements at the distal radius and tibia were generally lower compared to respective reported single-section μFE repeatability errors. Therefore, hFE is an attractive alternative to today's gold standard of μFE models and should especially be encouraged when analyzing multiple section measurements.
微有限元分析（μFE）是一种广泛应用于生物医学研究的工具，用于评估测量部位（包括超远端桡骨和胫骨）的骨体内机械性能。基于松质骨均匀本构模型的有限元方法（hFE）为临床应用提供了一种有吸引力的替代方法，因为它比传统的 μFE 计算成本更低。用于体内骨强度估计的患者特定模型通常基于标准的临床高分辨率外周定量 CT（HR-pQCT）测量。它们包括大约 10 毫米高的扫描区域，被称为单节段。已经表明，这些小的外周骨节段不能可靠地覆盖 Colles 骨折中的骨折线，因此不能可靠地覆盖桡骨的最薄弱区域。最近引入的多节段（多个相邻的单节段）测量可能会改善骨强度的评估，但对于 hFE 估计的重复性知之甚少，特别是对于多节段测量方案。因此，本工作的目的是量化远端桡骨和胫骨 HR-pQCT 重建的多节段 hFE 临床体内骨强度测量的重复性。
对 19 名健康的瑞士女性（43.6y±17.8y）和 20 名男性（48.2y±19.4y）进行了 61μm 各向同性体素分辨率的 HR-pQCT 检查。每位受试者首先使用双节段（336 个切片）在远端桡骨处扫描三次，然后使用三节段（504 个切片）在远端胫骨处扫描三次。对多节段 HR-pQCT 重建进行运动伪影分级，并生成非线性 hFE 模型（桡骨和胫骨）和线性 μFE 模型（仅桡骨），以估计刚度和极限载荷。然后，以均方根变异系数（CV）的形式计算体内重复性误差。
与胫骨（S：1.21%，F：1.45%）相比，桡骨的非线性 hFE 刚度（S）和极限载荷（F）的体内重复性误差（S：2.71%，F：2.97%）明显更高。桡骨的多节段线性 μFE 重复性误差（S：5.38%，F：10.80%）明显高于 hFE。
讨论/结论：与各自报道的单节段 μFE 重复性误差相比，远端桡骨和胫骨多节段测量的 hFE 结果的重复性误差通常较低。因此，hFE 是 μFE 模型的当今金标准的有吸引力的替代方法，特别是在分析多节段测量时，应鼓励使用 hFE。
