Bone microarchitecture assessment: current and future trends

Bone mineral measurements are frequently used to diagnose metabolic bone diseases such as osteoporosis. Before the age of 50, it affects only a few, whereas in old age, few are left without fractures due to ageor diseaserelated reduction of bone strength. Although many older persons may lose bone, as expressed by a decrease in bone density, not all develop fractures. This is not unexpectedly so, as bone density is not the sole determinant of fracture risk. Neuromuscular function and environmental hazards, influencing the risk of fall, the force of impact, as well as bone strength are equally important factors. Bone mineral density, geometry of bone, microarchitecture of bone and quality of the bone material are all components that determine bone strength as defined by the bone’s ability to withstand loading. On average, 70 to 80% of the variability in bone strength in vitro is determined by its density. On an individual basis, density alone accounts for 10 to 90% of the variation in the strength of trabecular bone [1]. This also means that 90 to 10% of the variation in strength cannot be explained by bone density. Recent data have shown that predicting trabecular bone strength can be greatly improved by including microarchitectural parameters in the analysis [2, 3]. However, the relative importance of bone density and architecture in the etiology of bone fractures, an issue referred to as bone ‘‘quality,’’ is poorly understood.