Compared with a pointed rifle bullet, spherical pellets slow rapidly in its flight through air or tissue. In tissue, the entire wounding potential of a shot pellet at its entrance velocity is likely to be delivered to the target, often with no exit wound. At close range (less than 3 m), shotgun pellets remain tightly clustered. Therefore, shot pellet size makes little difference, as the entire load of the pellets functions as a unit, with a velocity virtually equal to muzzle velocity. Shotgun wounds at ranges of less than 5 m consist of multiple parallel wound channels. This grossly disrupts the blood supply to tissue between the wound channels.
The most severe civilian firearm wounds typically seen are those inflicted by a shotgun from close range. After a close-range or contact shotgun wound to the trunk, external examination of the patient, particularly after adequate volume resuscitation, often does not disclose the severity of the internal injuries present.
Major neural injury after shotgun wounding of the extremities may be more important than fracture or major vascular injury in determining the final outcome. 24
During surgical exploration of a close-range shotgun wound, it is important to search for wadding, casing debris, plastic shot cup, and surface materials carried into the wound (e.g., clothing, glass, or wood). Many of these are radiolucent.8
Diagnosing long-range injury on the basis of the pattern of pellet spread is sometimes problematic. When shotgun pellets are tightly clustered or widely spread out, close-range injury or long-range injury (respectively) is usually suspected. However, in close-range injuries, the "billiard ball" effect may cause considerable pellet spread.25 When the tightly clustered group of shot at close range contacts the skin, the pellets at the front of the group are slowed. The pellets behind them in the group strike the pellets in front with an effect like a billiard ball break. This causes much more pellet spread in tissue than would be expected at close range. On radiographs, particularly in trunk wounds, this effect can simulate the pellet spread of a longer-range injury. 25 This pitfall can be avoided if the skin physical examination is correlated with the radiologic findings. If there is only one entrance wound hole, it is a close-range injury. If the distribution of the multiple skin entrance wounds is the same as the pellet spread on the radiograph, the injury occurred at longer range.
Recently manufactured BB guns and air guns that fire small pellets have considerably higher muzzle velocity [600 ft/s (183 m/s) or more] than older guns of this type. Penetrating injuries from these weapons are sometimes fatal. These air guns should not be considered toys. It is possible for someone to have been shot with a BB pellet that has penetrated the scalp, skull, and brain and think only a scalp wound is present. 26
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