Decision to amputate
The extent of the “zone of injury” is dependent upon the mechanism of injury (i.e., blast, gunshot, and crush injuries), as well as the co-morbidities and physiologic status of the casualty. Factors such as severe blood loss with massive resuscitation, burns, compartment syndrome, tourniquet use, and contamination load often extend the actual amount of tissue damage beyond that which is apparent on initial visual inspection.
Amputation terminology includes traumatic amputations, which are immediate extremity amputations caused by the wounding mechanism itself. Primary amputations are those performed by a surgical team after evaluation of the mangled extremity, with the decision not to pursue limb salvage for whatever reason. Secondary amputations can occur early (within 90 days) or late (after 90 days), with the latter referring to those amputations occurring after an initial attempt at limb salvage has been undertaken. Most commonly, primary and early secondary amputations are performed for vascular injuries not amenable to repair or resulting in prolonged limb ischaemia, nerve injuries not compatible with a functional extremity, or extensive nonviable tissue with potential for uncontrolled sepsis. Late secondary amputations are generally performed due to patient preference or major complications (e.g., flap failure, recurrent osteomyelitis, persistent poor function or pain) of attempted limb salvage. Current consensus regarding extremity amputation following battle injury is to preserve limb length and vascularity, facilitate adequate wound drainage, and achieve eventual coverage and closure of the amputation wound.
Although a number of scoring systems to predict the need for amputation exist, none is widely accepted or validated in the combat trauma population. Intact or the potential to restore perfusion (by vascular repair or shunt) may be the first determinant. If perfusion can be restored, any decision regarding amputation for nerve or bone loss can potentially be deferred until later, with the structurally unstable limb stabilized for transport by splinting or external fixation. Given the time sometimes required to restore perfusion, amputation may be necessary as a damage control procedure in a massively injured patient.