Abstract
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, we proposed the Ellipsoid Factor (EF) 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.
Competing Interest Statement
MD was a member of the Editorial Board of Royal Society Open Science at the time of submission and was not involved in the assessment of this submission.
Footnotes
This version contains revisions made based on the peer-review comments made during the submission of this article to Royal Society Open Science. In brief, we have added a clarifying figure, explained several parts of the text better, expanded the discussion, fixed a few typos, and reported the statistical results in a more consistent way.