Bone necrosis due to decompression

Death of areas of long bone has been known to be associated with work in compressed air and diving for many years. Detection and diagnosis require specialist knowledge, but familiarity with the condition has increased markedly over the last 20 years. Most of it is symptomless and causes no disability, but if areas adjacent to the joint surfaces of the upper end of the humerus and the upper end of the femur are affected, the joint may be seriously damaged and disability ensue. This problem has been defined by surveys of groups of workers using compressed air and divers in an attempt to establish prevalence. In general the more diving undertaken and the deeper the dives, the more probability there is of acquiring bone damage. The commonest area to be affected is the lower end of the femur, but the knee joint is never involved. The cause of bone damage is far from clear. None of the various explanations that have been offered are satisfactory, but research continues into the problem both in humans and in animals, particularly the miniature pig. At present it is difficult to quantify the risk taken by commercial divers in relation to changing technology either in terms of depth or duration of pressure.