Pattern and mechanism of traumatic amputation by explosive blast.

The mechanism of traumatic amputation of limbs by explosion is presented. A survey of blast casualties from Northern Ireland revealed that amputations through joints were very uncommon--the principal site was through the shaft of the long bones. Computer modelling of a bone exposed to blast forces reinforced the hypothesis developed from the casualty survey, that the primary mechanism of the bone injury was the direct coupling of the blast wave into the tissues. The fracture occurs from the resulting axial stresses in the bone, prior to limb flailing from the gas flow over the limb. The gas flow completes the amputation. Field trials employing a goat hind limb model have confirmed the hypothesis. Having identified the mechanism, concepts to develop protective clothing may now be proposed.