L Cannon. Behind Armour Blunt Trauma - An Emerging Problem.

Behind Armour Blunt Trauma (BABT) is the non-penetrating injury resulting from the rapid deformation of armours covering the body. The deformation of the surface of an armour in contact with the body wall arises from the impact of a bullet or other projectile on its front face. The deformation is part of the retardation and energy absorbing process that captures the projectile. In extreme circumstances, the BABT may result in death, even though the projectile has not perforated the armour. An escalation of the available energy of bullets and the desire of armour designers to minimise the weight and bulk of personal armour systems will increase the risk of BABT in military and security forces personnel. In order to develop materials that can be interposed between the armour and the body wall to attenuate the transfer of energy into the body, it is essential that the mechanism of BABT is known. There is a great deal of activity within UK and NATO to unravel the interactions; the mechanism is likely to be a combination of stress (pressure) waves generated by the rapid initial motion of the rear of the armour, and shear deformation to viscera produced by gross deflection of the body wall. Physical and computer model systems are under development to characterise the biophysical processes and provide performance targets for materials to be placed between armours and the body wall in order to attenuate the injuries (trauma attenuating backings TABs). The patho-physiological consequences of BABT are being clarified by research, but the injuries will have some of the features of blunt chest trauma observed in road traffic accidents and other forms of civilian blunt impact injury. The injuries also have characteristics of primary blast injury. An overview diagnosis and treatment is described. Introduction Behind armour blunt trauma (BABT) is the spectrum of non-penetrating injuries to the torso resulting from the impact of projectiles on personal armours. Although the armour may stop the actual penetration of the projectile through the armour, the energy deposited in the armour by the retarded projectile may be transferred through the armour backing and body wall. It may produce serious injury to the thoracic and abdominal contents behind the plate. With very high energy bullet impacts, the thoracic injuries may result in death. The existence of BABT as a clinical entity was first reported in 1978 by Carroll and Soderstrom among police officers wearing flexible body armour struck by handgun bullets. BABT may occur behind flexible textile-based armours and also behind rigid armours, principally constructed from ceramic materials. BABT has been identified as an emerging problem that has implications for the designers of personal armour systems, the operational performance of soldiers and for medical management of casualties.There are two principal reasons for its growing prominence: • An increase in the calibre and available energy of bullets that may be used in peace-keeping and other operational scenarios; • The desire of the designers of personal armour systems to reduce the weight and thickness of soft armours and armour plates a strategy that plainly will buy benefit in terms of the burden on military personnel, but will exacerbate the problem of dissipating the energy in the armour system. Armours are designed to absorb energy but the rapid deformations of the armours may result in a greater proportion of the energy of the retarded projectile being propagated into the body. The energy transferred from armours may be absorbed, dissipated or redistributed using materials placed between the armour system and the body these materials are called Trauma Attenuating Backings (TABs). There is research activity within NATO to develop the scientific basis for the design of TABs. This paper outlines the current views on the pathophysiology and biophysical mechanisms of BABT, and describes Surg Lt Cdr L Cannon, BSc MB BS FRCS Dip Sports Med RN Orthopaedic Specialist Registrar Orthopaedic Dept, Queen Alexandra Hospital, Cosham, Hants, PO6 3LY J R Army Med Corps 2001; 147: 87-96 Behind Armour Blunt Trauma an emerging problem L Cannon group.bmj.com on June 16, 2017 Published by http://jramc.bmj.com/ Downloaded from