Changes in trabecular micro-architecture are key to our understanding of osteoporosis. Previous work focusing on structure model index (SMI) measurements have concluded that disease progression entails a shift from plates to rods in trabecular bone, but SMI is heavily biased by bone volume fraction. As an alternative to SMI, Ellipsoid Factor (EF) has been proposed as a continuous measure of local trabecular shape between plate-like and rod-like extremes. We investigated the relationship between EF distributions, SMI and bone volume fraction of the trabecular geometry in a murine model of disuse osteoporosis as well as from human vertebrae of differing bone volume fraction. We observed a moderate shift in EF median (at later disease stages in mouse tibia) and EF mode (in the vertebral samples with low bone volume fraction) towards a more rod-like geometry, but not in EF maximum and minimum. These results support the notion that the plate to rod transition does not coincide with the onset of bone loss and is considerably more moderate, when it does occur, than SMI suggests. A variety of local shapes not straightforward to categorise as rod or plate exist in all our trabecular bone samples.

中文翻译：

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小梁骨丢失的由板到杆的过渡难以捉摸

小梁微结构的变化是我们了解骨质疏松症的关键。先前专注于结构模型指数（SMI）测量的工作得出的结论是，疾病的进展需要使小梁骨的板块向杆状转变，但是SMI受到骨体积分数的严重影响。作为SMI的替代方法，提出了椭球因子（EF）作为板状和杆状两个极端之间的局部小梁形状的连续量度。我们研究了在废弃骨质疏松症小鼠模型以及不同骨体积分数的人椎骨模型中，EF分布，SMI和小梁几何形状的骨体积分数之间的关系。我们观察到EF中位数（在小鼠胫骨疾病后期）和EF模式（在骨体积分数低的椎骨样本中）向着更像杆状的几何结构的适度变化，但在EF最大值和最小值中没有变化。这些结果支持这样的观点，即板到杆的过渡与骨质流失的发作并不相符，并且当发生时比SMI所建议的要适度得多。我们所有的小梁骨样本中都存在各种不容易归类为棒状或板状的局部形状。