[Thermal skin and bone necrosis following injury with an ultrasound bonding machine]

The article reports on a case of cutaneous gangrene and osteonecrosis resulting from thermal injuries inflicted by a high-frequency ultrasonic bonding machine used, for example, in the bonding of plastics. If high-frequency ultrasonic waves come in direct contact with the skin, a fraction of a second will suffice to produce heat and subsequent destruction even of deep tissue layers. The heat is produced by the absorption of mechanical vibrations, by reflection of these vibrations, and by surface friction. The heat, therefore, not only penetrates into the tissue, but is also generated in the deep tissue layers. The extent of the necrosis depends on the depth of penetration of the high-frequency ultrasonic waves. As with electrical burns, the necrotic tissue is excised with a margin of normal tissue and then covered by a skin graft.