Lacerations: formation, wound margins and descriptive terms
THE CONTEXT
Blunt impact displaces local tissue, creating traction that tears it. The resulting appearance reflects crushing, stretching and rubbing by the striking object.
Formation
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Local displacement by blunt impact sets up traction forces that tear tissues.
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Unless considerable force is used, most lacerations require a firm base that acts as an anvil against which skin and underlying tissues are pinned.
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In soft areas such as the buttock, thigh, calf, abdomen and upper arm, a projecting point or edge may cause laceration. A completely blunt object may also tear skin when pulled obliquely against its tension.
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Causes include blows from blunt objects, falls on hard surfaces, machinery and traffic accidents.
Appearance and interpretation
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The object crushes and stretches a broad skin area, which splits centrally. Crushing and tearing produce rough, irregular edges.
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Margins may be abraded by rubbing from the flatter part of the striking object and contused by bleeding into injured tissues.
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A single blunt blow can produce several lacerations. A blow to the side of the head may injure the parietal prominence, ear and lower jaw.
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Jagged projections may rip into skin in the manner of a blunt knife or axe.
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A vehicle wheel can produce avulsion, tearing skin away as a flap through its grinding action.
Descriptive terms
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Bleeding into adjacent tissues produces a contused laceration, also called a bruised tear.
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A laceration with abraded margins is an abraded laceration or scraped tear.
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Extensive bruising with laceration of deeper tissues is termed a crushing injury.