Skin Injuries

Three types of skin injuries are commonly seen: contusion (bruise), abrasion (scrape) and laceration (tear). Contusions have common characteristics (8-12). A contusion is manifest as skin discoloration from underlying extravasation of blood owing to blood vessel rupture as a result of trauma or disease (see Subheading 3.2. and Fig. 1). The surface is intact. Unlike "open" abrasions and lacerations, a contusion is "closed" and not liable to be infected. An abrasion occurs when the superficial skin layers are removed by friction, compression, or stretching (Fig. 2). A laceration is a tear of the tissue surface. A cutaneous laceration is distinguished from an incised wound caused by sharp force trauma by irregularity of the wound edge, strands of tissue bridging the

Fig. 1. Contusions of different ages. (A) Recent contusion; purple-red. (B) Healing contusion; brown. (C) Almost-healed contusion (arrow); yellow. (See Companion CD for color version of this figure.)
Fig. 2. Various abrasions. (A) "Brush" abrasions caused by relatively smooth surface (e.g., paved road). (B) Punctate and linear abrasions ("road rash") owing to more uneven surface (e.g., gravel road).
Fig. 3. Laceration. (A) Variable irregularity of wound edge. (B) Undermining and tissue bridging (arrow).

defect, and undermining (Fig. 3). The latter is caused by the lifting of the skin, which creates a pocket of soft tissue disruption.

Deformity and swelling are external signs of acute fracture (Figs. 4 and 5). A fracture can be confirmed by a postmortem radiograph (Fig. 5).

Fig. 4. Fractures of upper extremity. (A) Deformity owing to fracture of radius-ulna. (B) Swelling; fractured humerus.
Fig. 5. Elderly woman found dead on patio in winter. Hypothermia (see Fig. 9). (A) Shortened and externally rotated left leg. (B) "Paradoxical" undressing. (C) Postmortem radiograph-fractured left femur, which incapacitated victim.

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