Comments
Decompression sickness is either Type I (fatigue and joint pain) or Type II (severe injury to nervous and cardiopulmonary systems). Type I is also known as the bends or caisson disease. Joint pain in Type I may be mild or severe. [Cecil, p. 576] A late effect of decompression illness (caisson disease, the bends), dysbaric osteonecrosis is a form of aseptic bone necrosis. It is a disease of caisson workers and deep commercial divers but not usually recreational divers. The shoulder and hip are most commonly affected, and damage to the joint can lead to severe pain and disability. [Merck Manual, p. 3026] This disease may affect tunnel workers and deep sea divers. In asymptomatic workers with shaft lesions only, the disease can be detected by x-ray, bone scan or MRI. Approximately 11% of divers with 12 or more years of experience will show radiologic evidence of osteonecrosis. Divers who stay above 30 meters are rarely affected. [Rosenstock, p. 542-3] In the past, osteonecrosis of the femoral head was associated with caisson workers. With the adoption of standard decompression procedures, the main causes of this condition are now non-occupational. [LaDou, 4th edition, p. 64] Osteonecrosis occurs in Type 3 decompression syndrome, usually to the head or shaft of the humerus about 6-60 months after decompression. When the joint is not involved, it is usually asymptomatic but x-rays show bony sclerosis and mottling. Symmetric lesions are common. [Ladou, p. 192] These decompression procedures do not completely eliminate the risk of dysbaric osteonecrosis. Workers with at least one previous episode of the bends are more likely to have bony lesions. The most common sites are the distal femur and the proximal humerus, tibia, and fibula. "Workers with definite JA [justaarticular] osteonecrotic lesions should be advised to stop diving exposures and should be followed." [Rom, p. 1315-19]