shear

shear

[shir]

Etymology: AS, scearan, to cut

an applied force or pressure exerted against the surface and layers of the skin as tissues slide in opposite but parallel planes.

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shear [shēr]

an applied force that tends to cause an opposite but parallel sliding motion of the planes of an object. Such motions cause tissues and blood vessels to move in such a way that blood flow may be interrupted, placing the patient at risk for pressure ulcers. An example of a shearing force is seen when a patient slumps in a chair; the skin around the buttocks is stretched by the movement and interferes with circulation.

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shear,

n any force that causes slippage between a pair of contiguous articulated parts in a direction that parallels the plane in which they contact.

shear, inferior innominate,

n a condition in which the movement of the hipbone is restricted in upward and unrestricted in downward directions because the posterior and anterior superior iliac spines (PSIS and ASIS, respectively) are positioned below the contralateral points.

shear, inferior pubic,

n a condition in which one pubic bone is displaced below its normal mate.

shear, posterior pubic,

n a condition in which one pubic bone is displaced rearward of its normal mate.

shear, sacral,

n complex nonphysiologic translational sacral motion relative to the hipbones.

shear, superior innominate,

n a condition in which the movement of the hipbone is unrestricted in upward and restricted in downward directions because the posterior and anterior superior iliac spines (PSIS and ASIS, respectively) are positioned above the contralateral points.

shear, superior pubic,

n a condition in which one pubic bone is displaced above its normal mate.

shear, symphyseal (sim·f·sēlˑ shērˑ),

n condition in which the two halves of the symphysis slide over one other in a direction parallel to the plane in which they contact.

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shear,

n See strength, shear and strength, ultimate.

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shear

1. to remove the fleece of a sheep.

2. pressure on a mass in such a way that planes within it are pressured to move in a direction parallel to the pressure. Any movement is proportional to the distance from the plane at which movement occurs.

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shear injury

injury to tissues caused by shear pressure. See shearing injuries (2).

shear stress

the stress to which a tissue is subjected by a shear force without injury actually occurring.