Supplementary material from "Analysis of microscopic bone properties in an osteoporotic sheep model: a combined biomechanics, FE and ToF-SIMS study"

The present study deals with the characterization of bone quality in a sheep model of postmenopausal osteoporosis. Sheep were sham operated (n = 7), ovariectomized (n = 6), ovariectomized and treated with deficient diet (n = 8) or ovariectomized, treated with deficient diet and glucocorticoid treatment (n = 7). The focus of the study is on the microscopic properties at tissue level. The evaluation of the microscopic mechanical properties of osteoporotic bone by a combination of biomechanical testing and mathematical modelling plays a key role. Trabecular structure as well as mineral and collagen distribution in samples of sheep vertebrae were analysed by micro-computed tomography and time-of-flight secondary ion mass spectrometry. Sample stiffness and strength were determined by compression tests and finite-element analysis (FEA) of stress states was conducted. From this, an averaged microscopic Young's modulus at tissue level was determined. In the osteoporotic sheep model, a disturbed fibril structure in the triple treated group was observed, but bone loss only occurred in form of reduced trabecular number, thickness and cortical decline, while quality of the residual bone was preserved. The preserved bone tissue properties in the osteoporotic sheep model allowed for a FEA-based bone strength estimation similar to humans.