Musculoskeletal ImagingDysbaric osteonecrosis
also called caisson disease, bone lesions produced by exposure to high pressure environments, such as in scuba diving, underwater and space exploration, and off-shore oil drilling. Dysbaric
osteonecrosis can produce widespread skeletal alterations of epiphyseal, metaphyseal or diaphyseal segments of
tubular bones. This disorder has also been termed caisson disease, pressure-induced osteoarthropathy and barotraumatic osteoarthropathy.
Radiographically, the two major types of bone abnormalities are juxta-articular lesions, particularly in the head of the humerus and femur, and lesions of the diaphysis and metaphysis situated at a distance from the joint. The juxta-articular changes include radiodense areas resembling bone islands but slightly less discrete, a "snow-capped" configuration, radiolucent subcortical bands (crescent sign), and bone collapse and fragmentation (see crescent sign (III:1), Fig. 1). The abnormalities of the diaphyses and metaphyses consist of indistinct radiodense foci, irregular calcified areas with a shell-like configuration, and, rarely, radiolucent lesions. The sites involved most frequently are the distal shaft of the femur, the humeral head, the femoral head and the tibial shaft, in descending order of frequency.
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