Bone Abstracts

Hip fracture rate in Norway is the highest registered in World, and more than double that of Spanish women. Previous studies were unable to demonstrate significant differences between the two populations with respect to bone mass or calcium metabolism. In order to test, whether the difference in fracture propensity between both populations could be explained by differences in bone material quality we assessed bone material strength using microindentation in 41 Norwegian and 46 Spanish women with normal BMD-values (T-score >−1 and <+2,0), without clinical or morphometric vertebral fractures, no clinical or laboratory signs of secondary osteoporosis and without use of drugs with known influence on bone metabolism. Bone material properties were assessed by microindentation of the thick cortex of the mid tibia following local anesthesia of the area using the Osteoprobe® device (Active Life Scientific, Sta Barbara, CA). Indentation distance was standardized against a calibration phantom of methylmethacrylate and results, as percentage of this reference value, expressed as BMS (Bone Material Strength) units.

We found that the bone material properties reflected in the BMS value of Norwegian women was significantly inferior when compared to Spanish women (77.0±7.1% vs 80.7±7.8%, P=0,02). Total hip BMD was significantly higher in Norwegian women (1.218 g/cm² vs 0.938 g/cm² P=<0.001, but regression analysis revealed that indentation values did not vary with BMD (r=0.03, P=0.12) or age (r=0.04, P=0.42).

In conclusion Norwegian women show impaired bone material properties, when compared to Spanish women. This is the first demonstration of ethnical differences in bone material properties and could partly explain the much higher propensity for fracture in Norwegian women than in Spanish women.