OBJECTIVETo investigate the imaging features of dysbaric osteonecrosis.

METHODSThe imaging appearances of four patients with dysbaric osteonecrosis caused by diving, were analyzed retrospectively.

RESULTSIn four cases with dysbaric osteonecrosis including case 1 with stage I, case 2 with stage II, case 3 and case 4 with stage III, there were a case with the lesion in a bone and other 3 cases with lesions in multiple bones,and a case with the lesion in unilateral bone and 3 cases with the lesions in lateral bones. (1) The juxta-articular lesions: there were 10 long bones with the head lesions, including 6 humerus with the head lesions and 4 femurs with the head lesions in 4 cases. In four cases, 10 sclerosis lesions appeared in the heads of long bones, each case had a "snow-capped" sclerosis lesion for case 2, case 3 and case 4. There were 7 small radiolucent lesions and a large radiolucent lesion involved in femur neck. The ringlike, linear, bending and punctuate calcification lesions were found on CT films of case 2. The osseous collapse in one femur head and the fragmentations in three femur heads could be seen in case 3 and case 4; 2 crescent signs can be seen in the bilateral femur heads of case 4 with secondary osteoarthritis in left hip joint. (2) The diaphyseal and metaphyseal lesions: the X ray film of case 4 showed the streak and irregular calcifications in the shaft of right humerus; there are strip calcifications in diaphyseal and metaphyseal of the left humerus on MPR coronal view in case 2.

CONCLUSIONThe diagnosis of dysbaric osteonecrosis suggested that the increased bone density or sclerosis lesions appeared in the heads of long bones, and osteonecrosis lesions were found in multiple bones or lateral bones.