Shear and Friction Explained

Friction and shear are mechanical forces that contribute to pressure ulcer formation.

Whilst shear and friction are two separate phenomenons, they often work together to create tissue ischemia and ulcer development.

The Gel Ovations range of Dimensional Gel Pads are designed to prevent shear and friction from being exerted on the body, thereby helping to prevent and treat pressure ulcers.

Shearing force

A Shear injury will not be seen at the skin level because it happens beneath the skin.

Shear is a “mechanical force that acts on an area of skin in a direction parallel to the body’s surface. Shear is affected by the amount of pressure exerted, the coefficient of friction between the materials contacting each other, and the extent to which the body makes contact with the support surface.” ¹

“Think of this as pulling the bones of the pelvis in one direction and the skin in the opposite direction. The deeper fascia slides downward with the bone; the superficial fascia remains attached to the dermis.

This insult and compromise to the blood supply creates ischemia and leads to cellular death and tissue necrosis. Shear and friction go hand in hand—one rarely occurs without the other.”

Friction Injury

Unlike shear injury, friction injury is a visible phenomenon. Friction is the “mechanical force exerted when skin is dragged across a coarse surface such as bed linens.” ¹ T

A skin injury caused by friction looks like an abrasion or superficial laceration. Friction, however, is not a primary factor in the development of pressure ulcers. It can contribute to an insult or stripping of the epidermal layer of the skin, creating an environment conducive to further insult.

An alteration in the coefficient of friction increases the skin’s adherence to the outside surface (such as a bed or chair). Friction then combines with shearing forces and the ultimate outcome may be a pressure ulcer.

Tissues subjected to friction are more susceptible to pressure ulcer damage. The three mechanical forces (pressure, friction, and shear) may act in concert to create tissue damage.

Other patients at risk for pressure ulcers from friction are elderly people, those with uncontrollable movements, due to neurological conditions and those who use braces or appliances that rub against the skin.

References

1. Bergstrom N, Bennett MA, Carlson CE, et al. Treatment of Pressure Ulcers. Clinical Practice Guideline, No. 15. AHCPR Publication No. 95-0652. Rockville, MD: Agency for Health Care Policy and Research; December 1994.

Hess, Cathy Thomas BSN, RN, CWOCN Advances in Skin & Wound Care: June 2004 – Volume 17 – Issue 5 – p 222

Adapted from Ayello E, Baranoski S, Lyder C, Cuddigan J. Pressure ulcers. In: Baranoski S, Ayello EA, editors. Wound Care Essentials: Practice Principles. Springhouse, PA: Lippincott Williams & Wilkins; 2004. p 243.