The most common blunt force injury is the contusion (Fig. 19.26). The pattern contusion is one that helps identify the causative weapon. A blow from a linear object leaves a contusion that is characterized by a set of parallel lines separated by an area of central clearing (Fig. 19.27). The blood underlying the striking object is forcibly displaced to the sides, which accounts for the pattern’s appearance. Pattern injuries that an emergency physician should recognize include those caused by the hand (slap marks [Fig. 19.27], fingertip contusions [Fig. 19.28], grab marks, ligature marks [Fig. 19.30], fingernail abrasions), those caused by solid objects (baseball bat, tire iron, 2 by 4, belt, shoe, comb), and bite marks.
Periorbital Contusion. A contusion without a discernable pattern is the result of some type of blunt-force trauma. Victims of interpersonal violence frequently present with nonspecific, nonpattern contusions. A 24-hour-old cigarette burn is located on the victim’s right upper lid. This victim was held against her will for 48 hours and repeatedly beaten about the face. (Photo contributor: William S. Smock, MD.)
Slap-Mark Pattern Contusions. This victim of a “fall from the couch” has a pattern injury present on the right cheek. The pattern of central clearing surrounded by linear parallel contusions is pathognomonic for impact with a rounded linear object, in this case the extended fingers of a hand. (Photo contributor: William S. Smock, MD.)
Fingertip Contusion Pattern. This patient exhibits fingertip contusions. The emergency physician should never attempt to date the age of a contusion based upon its color. (Photo contributor: William S. Smock, MD.)
Tire Mark. This tire mark, a mirror image of the tire tread, was the only evidence that connected this pedestrian with the vehicle involved in the hit-and-run incident. (Photo contributor: William S. Smock, MD.)
Strangulation Ligature Belt Marks. Ligature marks from a belt, with petechial hemorrhage above the marks, supported the mentally challenged patient’s story of being “choked” by her caretaker. The majority of fatal strangulations do not exhibit external evidence of trauma. (Photo contributor: William S. Smock, MD.)
Other manifestations of blunt-force trauma to the skin are the abrasion and the laceration. A weapon with a unique shape or configuration may stamp a mirror image of itself on the skin (Fig. 19.29) and provide the emergency physician with additional information on the mechanism of the injury. The color ...