Trauma in elderly people: what proportion of fractures are a consequence of bone fragility?

Epidemiologists have tended to equate osteoporotic fractures with those which occur after only moderate trauma, or which affect elderly people. We set out to critically examine this epidemiological approach, because even among elderly people some fractures will be a result of severe trauma and these cannot be assumed to reflect bone fragility. In a population based study of all Cardiff residents aged over 60 we identified everyone who presented with a fracture during 1996. We considered the events that led to each fracture, to establish which fractures were a result of 'severe' trauma: trauma greater than a fall from a standing height. We identified 1335 people who between them sustained a total of 1372 fractures. 168 (12%) of the fractures resulted from severe trauma, but in people aged over 80 only 6% of all fractures, 4% of hip fractures, and 3% of wrist fractures followed severe trauma. In older subjects severe trauma makes only a very small contribution to the causation of fracture, so that the age-sex distribution of fractures following moderate trauma closely resembles that of fractures overall. For epidemiological purposes it does appear justifiable to equate the consequences of bone fragility with the occurrence of osteoporosis associated fractures in elderly people.