Frostbite

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Frostbite is a focal tissue injury from exposure to extremely low temperatures, and most commonly involves the fingers and toes. It is most commonly encountered in radiology in a differential for acro-osteolysis.

Pathology

Tissue injury from frostbite occurs in two ways :

direct tissue necrosis from freezing
indirect tissue injury from inflammatory changes and release of inflammatory mediators

Clinical presentation

Most common on exposed areas: hands, feet, face and ears. The skin changes texture ("waxy") and may develop bullae if the frostbite is severe.

Radiographic features

May be useful to help determine the degree of injury or presence of secondary injury in patients who present clinically with frostbite.

Plain radiography

acro-osteolysis of the distal phalanx / phalangeal tuft
swelling of affected soft tissues
it has been reported that the thumb may be relatively spared (patient likely to wrap thumb in palm)

Nuclear medicine

Tc-99m-MDP (bone scintigraphy)

a two-phase scan may be useful to assess the viability of tissue
- a combination of the perfusional phase and soft tissue phase can help characterize areas of inflammation and areas of ischemia (increased or decreased radiotracer activity, respectively)

MRI

limited data suggests that MRI may be a useful modality for demarcating ischemic tissue

Treatment and prognosis

Clinically, frostbite is classified similarly to burns: 1-4 degree.

Incautious thawing of the tissue may lead to worsened injury (higher degree burn) from the ensuing inflammatory reaction.

Treatment of systemic hypothermia should be prioritized over frostbite.

Differential diagnosis

frostnip: focal tissue injury without permanent damage
immersion foot: frostbite and immersion in water (a type of trench foot)