Benign Subcutaneous Emphysema of the Upper Extremity: NEJM c
A 59-year-old woman fell from a horse and injured her left elbow. Four days later she sought evaluation for persistent swelling of her arm. On examination, the patient had a small, clean wound over the olecranon; there were no signs of infection. Diffuse crepitus of the arm, extending to the left chest wall, was noted.

An oblique radiograph of the elbow (Panel A) and a posteroanterior radiograph of the chest (Panel B) demonstrated circumferential subcutaneous emphysema (arrows) of the upper extremity extending from the wrist to the left hemithorax. No rib fracture or pneumothorax was seen. The absence of air within muscle suggested that a deep, gas-producing soft-tissue infection was not present. The emphysema resolved without surgical treatment after one week.

Noninfectious causes of subcutaneous emphysema include perforation of the pulmonary or digestive tracts, blast injuries, cutaneous ulcers, air-gun injuries, dental extraction, and irrigation of wounds with hydrogen peroxide. In rare cases, large amounts of air can enter the soft tissues from small skin wounds, presumably as the result of a ball-valve mechanism.

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