Unusual Presentation of Dysbaric Osteonecrosis in the Humeral Metaphysis and Diaphysis: A Case Report with Spontaneous Regression

Osteonecrosis of the humerus typically involves the humeral head, whereas diaphyseal involvement is extremely rare.We report an unusual case of dysbaric osteonecrosis extending from the proximal metaphysis to the diaphysis of the humerus in a 47-year-old male professional industrial diver.The patient had worked in underwater industrial operations for over 20 years, with a history of more than 100 occupational dives, most commonly performed at depths shallower than 30 m and with dive durations of approximately 60 minutes, in accordance with decompression protocols.Despite the absence of shoulder pain or functional limitation, magnetic resonance imaging revealed an extensive intramedullary lesion measuring 11.4 cm in the humeral shaft.A 12-month follow-up magnetic resonance imaging demonstrated spontaneous regression of the lesion to 9.5 cm with decreased perilesional activity.This case highlights that dysbaric osteonecrosis can occur in atypical diaphyseal locations and may follow a benign clinical course with conservative observation.