Fingernail mark distortion, grazes and friction burns
THE CONTEXT
Movement across the skin produces characteristic abrasion patterns. Skin recoil can alter nail marks, while grazing and friction injuries have distinct surface appearances.
Fingernail marks
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Dragging fingers down the skin may produce parallel linear scratches.
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Nail indentation puts the skin under lateral tension. After release, elastic recoil returns the skin toward its original position and carries the nail mark with it.
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The curve may reverse or become straight, although this does not always occur. Pointed nails are more likely than straight-edged nails to produce these paradoxical appearances.
Grazes
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Grazes, also called sliding, scraping or grinding abrasions, are the most common abrasion type and result from movement between skin and a rough contacting surface.
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They show uneven longitudinal parallel grooves or furrows, with epithelium heaped at their ends indicating the direction of force.
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The skin at the start may be uniformly denuded or serrated, and the epidermis is scraped away, destroyed or detached.
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Grazes commonly occur in road accidents and may also follow a glancing kick from a boot.
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Many extend into the dermis and bleed because of the corrugated dermal papillae. Deep abrasions have a punctate or spotty appearance.
Brush burns and friction burns
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Violent tangential rubbing, such as dragging over the ground, can produce a brush burn or gravel rash: a scraping injury over a large area.
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A friction burn, also termed a scuff or brush abrasion, is an extensive superficial reddened excoriated area without serous ooze or bleeding and with little or no linear mark.
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Friction burns may follow tangential contact with a smooth surface or occur when the skin is covered by clothing.