Wound ballistics of firearm-related injuries—Part 1: Missile characteristics and mechanisms of soft tissue wounding

Abstract

Firearm-related injuries are caused by a wide variety of weapons and projectiles. The kinetic energy of the penetrating projectile defines its ability to disrupt and displace tissue, whereas the actual tissue damage is determined by the mode of energy release during the projectile–tissue interaction and the particular characteristics of the tissues and organs involved. Certain projectile factors, namely shape, construction, and stability, greatly influence the rate of energy transfer to the tissues along the wound track. Two zones of tissue damage can be identified, the permanent cavity created by the passage of the bullet and a potential area of contused tissue surrounding it, produced mainly by temporary cavitation which is a manifestation of effective high-energy transfer to tissue. Due to the complex nature of these injuries, wound assessment and the type and extent of treatment required should be based on an understanding of the various mechanisms contributing to tissue damage.

“Dans les champs, le hasard ne favorise que les esprits préparés” (In the field [of observation], chance favours only the prepared mind)

The wounding power of firearms is an important issue in penetrating trauma, both war and civilian, and as such it may also affect surgeons with little knowledge or concern about weapons and their effects. The study of these effects produced by missiles has been termed ‘wound ballistics’, indicating its subordination to the science of projectile motion. In this context, the term missile implies small projectiles capable of tissue penetration because of their energy rather than their shape. Wound ballistics examines the relationship between the properties of the missile and the severity of the resultant wound, and the role of the various mechanisms of ballistic penetration in the production of tissue damage. These aspects apply to battle casualties, the majority of which are caused by munition fragments rather than bullets, as well as to ballistic injuries seen during peacetime.

In both of these environments, the maxillofacial region represents a prominent location for missile injuries, but it is mainly due to civilian firearm violence that this area often appears as an intentional close-range target, whether the consequence of assault or suicide attempt. In the face, the close anatomical relationship of soft and hard tissues results in a complex pattern of firearm-related injuries, with comminution of bone and teeth as a common feature. Furthermore, the amount of non-viable tissue following ballistic trauma remains a critical concern, especially when primary reconstructive procedures are contemplated. Although the assessment of the unique consequences of these injuries is a subject of surgical judgement, an understanding of wound ballistics can provide the basis for interpretation of the mechanism of tissue damage with respect to its extent along the wound track; in this way the surgeon is also prepared for potential complications. In this paper, the first of two, we present the wounding effects of small arms projectiles on soft tissue. In the second part, the pathophysiology and ballistic aspects of maxillofacial missile injuries are discussed.

Wounding agents

Firearm-related injuries among the civilian population are commonly inflicted by handguns, rifles, and shotguns. These weapons are included under the military term ‘small arms’, and are generally defined by their type and calibre (diameter).

Handguns and rifles

Both handguns and rifles are rifled firearms. Rifling is an important feature of all firearms except shotguns, indicating a series of spiral parallel grooves cut into the bore (the inner surface of the barrel). Calibre refers both to the diameter of the bore and the bullet maximum diameter. It is expressed either as a decimal fraction of an inch (with the nought in front of the decimal point usually omitted) to designate American and British weapons and cartridges, or in millimetres based on the metric designation system, which is the standardized method for sizing military ammunition.

Handguns are of two major types, revolvers and auto-loading pistols. They are the most frequently used type of firearm in civilian conflicts. Common handgun calibres range from .22 to .45 in. ( Fig. 1 ). The more rarely encountered submachine guns are truly automatic weapons typically using handgun ammunition.

Fig. 1
Examples of pistol ammunition. From left to right: .38 Super; 9-mm Luger; .40 Smith & Wesson (S&W); .45 Automatic Colt Pistol (ACP). The former two are essentially of the same diameter, but the .38 Super is more powerful as indicated by its considerably longer cartridge case containing larger propellant charge. Note also the truncated ‘semiwadcutter’ (SWC) configuration of the .40 S&W compared to the more common round nose shape of the other bullets. (One cent coins are shown for comparison.).
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Jan 19, 2018 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Wound ballistics of firearm-related injuries—Part 1: Missile characteristics and mechanisms of soft tissue wounding
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