Lower extremity avulsion injuries.
Avulsion injuries are best treated by removal of the avulsed tissue and replacing it as a full-thickness skin graft. Additional meshed split-thickness skin grafts from a separate donor area may be necessary to complete the soft-tissue coverage. Fractures commonly accompany avulsion injuries and require appropriate treatment. The atypical avulsion injury is a special problem that occurs infrequently but results in considerable morbidity. This injury is most commonly seen in individuals run over by heavy vehicles, particularly buses. The shearing forces involved cause extensive undermining of tissues, although the external surface of these areas appears uninvolved. This results in an under-estimation of the true extent of the injury. If not recognized, there may be either delayed full-thickness necrosis of large areas of skin and subcutaneous tissue or the development of sepsis due to deep necrosis of the fat and fascia at the shear plane. If the true extent of injury is initially recognized, a dilemma exists in terms of deciding how much of the normal-appearing tissue to excise. The proper treatment plan for the atypical injury is not yet established with certainty. However, quantitative dermofluorometry has proven to be a valuable means of assessing the viability of extensively undermined areas of skin and subcutaneous tissue. This test is easily performed and can be used for serial study. Viable areas that are undermined and left in place require an early limited debridement of the undersurface to remove necrotic fascia and subcutaneous fat. This may require additional incisions for exposure. Plantar avulsions are another separate category of avulsion injury. Traditionally, the avulsed plantar surface has been sewn back into place, although this frequently resulted in the loss of this specialized tissue. It has become clear that it is possible to revascularize the plantar surface when major avulsion injuries occur. The plantar surface is thus similar to digital amputations and major scalp avulsion injuries in that replantation or revascularization is worthwhile and should be performed whenever possible. Soft-tissue loss around the ankle frequently co-exists with these injuries, and free tissue transfer may be necessary to complete soft-tissue coverage following revascularization.