Bruise distribution and differentiation from hypostasis
THE CONTEXT
The distribution of bruises may suggest how force was applied. Incision findings and tissue appearance help distinguish bruising from hypostasis.
Interpretation of distribution
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Bruise size may help assess the degree of violence, while distribution may suggest the character and manner of injury.
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Grasping an arm may produce three or four finger bruises on one side and a larger thumb bruise opposite them; this pattern may indicate the assailant's position.
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Arm bruising may indicate restraint. Shoulder-blade bruising indicates firm pressure against the ground or another resisting surface.
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In manual strangulation, the position and number of bruises and nail marks may indicate the method of attack.
Hypostasis
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Hypostasis results from distension of dermal vessels with blood and affects extensive areas of the most dependent parts.
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The affected area is not elevated or abraded, has clearly defined margins and is uniformly bluish-purple.
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On incision, blood remains within vessels and can be washed away easily; subcutaneous tissues are pale.
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Hypostasis is absent in areas subjected even to slight pressure.
Bruising
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Bruising results from rupture of superficial or deep vessels and occurs at or around an injury, potentially anywhere on the body.
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Bruises are often swollen from extravasated blood and oedema, may be abraded and have margins merging with surrounding tissue.
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Older bruises show different colours; fresh bruises may appear more intense than adjacent hypostasis.
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Incision reveals firmly clotted extravasated blood that cannot be washed away by a gentle stream of water. Subcutaneous tissues are deep reddish-black.
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A bruise may be slightly lighter over an area of pressure or support.