Avascular Bone Necrosis
This is a serious disease of bones that is also called avascular necrosis or dysbaric osteonecrosis. There are a number of causes of bone necrosis but exposure to hyperbaric conditions is the usual reason when it occurs in someone who dives or has dived in the past. Until recently it was though to be an occupational illness occurring in only professional divers and caisson workers. However in the last few years the members of the UKSDMC have become aware of cases occurring in amateur divers.
The Committee therefore wish to bring this condition to the attention of all amateur divers. The disease can occur months, years or even decades after hyperbaric exposure. In essence the disease causes areas of bone to die. If these dead areas of bone are next to a joint this can result in severe joint damage and this may make joint replacement necessary. When a dead area affects the shaft of a bone it causes no symptoms, but there is still cause for concern because bone necrosis can change to a form of bone cancer. The cause of dysbaric osteo-necrosis is unknown. There is no proven association with decompression illness, though both can affect joints and the risk of each condition is related to the degree of exposure to hyperbaric conditions.
The incidence of dysbaric osteon ecrosis increases with depths of dives, their duration and the number of exposures. Amateur sport SCUBA divers were considered to be at low risk because their dives were usually short and shallow. As amateur divers go deeper, for longer and use gas mixtures containing helium it is probable that more cases of dysbaric osteonecrosis will come to light.
Failure to learn from past lessons may cause amateur divers to suffer an epidemic of bone necrosis, similar to those in caisson workers in the last century and in professional divers earlier in this century, before safer work practices were introduced to those occupations.