Strontium and fluoride treatment play a role as therapeutic options to antagonise fracture risk in osteoporosis. Incorporation of these elements in bone is accompanied by changes in remodelling, matrix composition and structure. However, a direct comparison of the effectiveness of strontium and fluoride treatment in human cortical bone with a focus on its mechanical properties remains to be established. Iliac crest bone biopsies obtained from autopsy cases without bone disease served as healthy controls. The study groups encompass iliac crest biopsies from treatment naïve osteoporosis cases, patients with diagnosed osteoporosis under sodium fluoride (NaF) or strontium ranelate (SrR) treatment. Using instrumental neutron activation analysis (INAA), a positive correlation between treatment period and uptake of strontium and fluoride was found. Quantitative backscattered electron imaging (qBEI) was carried out to investigate the degree of mineralisation and the cortical porosity. NaF- and SrR-treated patients showed a lower porosity of 10.9±7.7% and 10.3±6.2% in comparison to osteoporotic patients (18.1±13.2%) indicating an increased bone mass. The lowest porosity of 4.4±1.8% was observed in healthy controls. NaF and SrR treatment led to significantly higher bone mineralisation in comparison with treatment naïve osteoporotic bone (+9.2% and +9.5% in mean calcium content), while the highest mineralisation pattern was found in iliac crest cortices of healthy controls. Mechanical properties were assessed via reference point indentation (RPI) as a surrogate measure of bone toughness. RPI showed that incorporation of strontium and fluoride in comparison with non-treated osteoporotic individuals led to significantly decreased indentation distance indices as a measurement of bones resistance to deformation and micro-fractures. Healthy controls showed the highest resistance. In conclusion, we found that osteoporosis treatment with both NaF and SrR had positive effects on mechanical characteristics beyond a gain in bone mass but did not resemble the properties of healthy cortical bone in the iliac crest.
Disclosure: The authors declared no competing interests.