Content area
Abstract
This study sought to characterise the effect of bone turnover on bone quality and material properties, in an ovariectomised (OVX) ovine animal model at 12 months post-surgery. A study of compact bone turnover and microarchitecture, using epifluorescence microscopy and micro CT respectively, was carried out on the left metatarsal. Bone turnover was increased in the OVX group compared with controls. Increased turnover resulted in increased porosity in the OVX group compared to controls. The small reduction in strength resulting from these changes compared well with our calculations which were based on the reduction in load bearing area. Analyses of fatigue-induced microdamage in control and OVX compact bone samples showed that while numerical crack density was higher in OVX, crack surface density was higher in the controls, due to the presence of more long microcracks. It was also observed that long cracks (>300μm) tended to stop at new (labelled) osteons whereas they tended to penetrate or deflect around older (unlabelled) osteons. This shows that increased turnover has a direct effect on microcrack behaviour in bone. Histomorphometry of the L3 vertebra revealed increased bone turnover in cortical and trabecular compartments in OVX bone compared with controls. Biomechanical testing showed that ultimate strength and stiffness were reduced in the OVX group. This group also displayed less plastic strain and more strain due to damage compared with controls. Although no change was found in BMD as measured by DEXA, significant changes were found in bone quality parameters 12 months post-OVX. In conclusion, this study has illustrated the importance of bone turnover in relation to bone quality.
