Assessment of tissue viability after frostbite injury by technetium-99m-sestamibi scintigraphy in an experimental rabbit model

Frostbite causes injury to the tissue by direct ice-crystal formation at th e cellular level with cellular dehydration and microvascular occlusion. Mus cle that initially appears viable on reperfusion may subsequently become ne crotic because of microcirculatory collapse. Since muscle is a sensitive ti ssue in frostbite injury, we used technetium-99m-sestamibi limb scintigraph y to assess tissue viability in an experimental rabbit model. Twelve rabbit s were used for this investigation. The right hind limb of the rabbits was immersed to the ankle joint in a container filled with 90% ethanol at -25 d egrees C for 10 min. Frostbitten limbs were allowed to thaw in air at room temperature. Imaging and pathological examination of the affected limbs wer e performed 2 h, 24 h, 48 h and 72 h after freezing. In 2-h images, initial hypoperfusion was seen that corresponded to circulatory collapse. In 24-h images, there was hyperperfusion (so-called period of temporary reperfusion ), corresponding to circulatory restoration. In 48-h images, a second hypop erfusion corresponded to viable but ischaemic tissue. In 72-h images, there was non-perfusion of the limb that correlated with the pathologically dete rmined diagnosis of necrosis. All scintigraphic patterns correlated with pa thological findings. We suggest that these scintigraphic patterns in soft t issue may be helpful in distinguishing between frank infarction and reversi ble ischemia and therefore may be useful in selecting early therapeutic or surgical interventions to salvage bone and soft tissue. Further studies ape needed to show the usefulness of Tc-99m sestamibi scintigraphy in clinical frostbite cases.