Bone mass and beyond: risk factors for fractures

Numerous prospective studies have demonstrated a strong relationship between bone mass and fracture risk. The fact that the bone mass distributions of fracture and nonfracture cases overlap does not necessarily indicate a shortcoming of bone mass, but might instead be due to the sporadic nature of falls and the influence of other fracture risk factors. The recent finding that prevalent fractures are strong predictors of fracture risk, independent of bone mass, suggests (but does not prove) that there may be other, potentially measurable fracture risk factors that complement, and act independently of, bone mass. This paper reviews possible mechanisms by which prevalent fractures might serve as etiologic risk factors, or as surrogate indicators of other risk factors. Potential risk factors other than bone mass and prevalent fractures are also considered. Whether or not etiologic fracture risk factors other than bone mass can be identified, it appears that treatments that influence bone will be most effective if begun early, before bone strength becomes impaired and fractures begin to occur.