Musculoskeletal Imaging

Frostbite

a condition resulting from thermal injury in which freezing of tissues leads to radiographically detectable local musculoskeletal alterations. In this disorder, blood vessels are injured severely or irreparably and the circulation of blood ceases. The vascular beds within the frozen tissue become occluded by thrombi and cell aggregations. Tissues in superficial locations (ears, nose, digits) undergo increasing damage from the formation of tiny ice crystals.

Within the injured areas, transudation of fluid, perivascular oedema, intravascular stasis, agglutination of erythrocytes and deposition of fibrin take place.

In the bones and joints, soft tissue swelling and loss of tissue are seen initially, especially at the tips of the digits; osteoporosis and periostitis may occur at a slightly later stage. Sparing of the thumb is characteristic, perhaps from clenching the fist with the thumb clasped in the palm during the exposure to cold (Fig.1). Interphalangeal joint abnormalities may eventually simulate those of osteoarthritis. Joint space narrowing, sclerosis, osteophytosis, soft tissue hypertrophy and tuftal resorption of terminal phalanges can be seen.

Arteriography is useful in the diagnosis and treatment of frostbite. In addition, bone scintigraphy reveals the uptake of radionuclide in the region of frostbite, although this depends on the integrity of the vascular tree. Persistent perfusion defects indicate nonviable tissue, whereas reperfusion, which may be evident on studies performed weeks after the injury, indicates tissue viability.

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Fig.1

PA radiograph demonstrates acro-osteolysis bilaterally with relative sparing of the thumbs. (Courtesy of Tom Broderick, MD, Orange, CA)
Frostbite, Fig.1