Determining the wounding effects of ballistic projectiles to inform future injury models: a systematic review.

INTRODUCTION: Penetrating wounds from explosively propelled fragments and bullets are the most common causes of combat injury experienced by UK service personnel on current operations. There is a requirement for injury models capable of simulating such a threat in order to optimise body armour design. METHOD: A systematic review of the open literature was undertaken using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses methodology. Original papers describing the injurious effects of projectiles on skin, bone, muscle, large vessels and nerves were identified. RESULTS: Projectiles injure these tissues by producing a permanent wound tract (PWT), comprised of a central permanent wound cavity, in conjunction with a zone of irreversible macroscopic tissue damage laterally. The primary mechanism of injury was the crushing and cutting effect of the presented surface of the projectile, with an additional smaller component due to macroscopic damage produced by the radial tissue displacement from the temporary tissue cavity (TTC). No conclusive evidence could be found for permanent pathological effects produced by the pressure wave or that any microscopic tissue changes due to the TTC (in the absence of visible macroscopic damage) led to permanent injury. DISCUSSION: Injury models should use the PWT to delineate the area of damage to tissues from penetrating ballistic projectiles. The PWT, or its individual components, will require quantification in terms of the amount of damage produced by different projectiles penetrating these tissues. There is a lack of information qualifying the injurious effect of the temporary cavity, particularly in relation to that caused by explosive fragments, and future models should introduce modularity to potentially enable incorporation of these mechanisms at a later date were they found to be significant.