How To Apply a Cast

• Fractures

• Other injuries (eg, unstable sprains or dislocations) requiring immobilization

• Acute fractures or dislocations at risk of continued swelling that could develop ischemia caused by compartment syndrome after excessive tightness of circumferential casting

• Thermal injury (caused by the exothermic reaction of plaster or fiberglass hardening)

• Pressure sores, neurapraxia, and/or ischemic injury (caused by excessive pressure)

• Compartment syndrome (sometimes caused, in part, by excessive tightness of circumferential wrapping)

• Stockinette

• Roll padding

• Plaster or fiberglass casting material*

• Strong scissors and/or shears

• Lukewarm water and a bucket or other container

• Nonsterile gloves

* Both materials are equally effective. Choice depends on availability and user preference. Length and width of materials depend on the body part being immobilized.

• The patient should be positioned so that the operator has appropriate access to the affected extremity.

• The extremity should be positioned in the appropriate anatomic alignment for the specific injury.

• Choose stockinette of the appropriate width; it should be form fitting but not so tight that it compromises circulation.

• Apply stockinette to cover the area (eg, about 5 to 10 cm) proximal and distal to the anticipated extent of casting material.

• Apply several layers of padding (typically, 4).

• Wrap the padding circumferentially, from distal to proximal, over the area to which the cast will be applied. Overlap the underlying layer by half the width of the padding.

• Apply the padding firmly against the skin without gaps but not so tightly that it compromises circulation.

• Extend the padding slightly (about 3 to 5 cm) past the anticipated extent of the plaster or fiberglass.

• Smooth the padding as necessary to avoid protrusions and lumps. Tear away some of the padding in areas of wrinkling to smooth the padding.

• Add separate, non-circumferential pieces of padding over and around bony prominences.

• Immerse the casting material in lukewarm water.

• Gently squeeze excess water from the casting material. Do not wring out plaster.

• Apply the casting material circumferentially from distal to proximal, overlapping the underlying layer by half the width of the casting material.

• Use 8 to 10 layers of plaster (typically) or 2 to 4 layers of fiberglass to ensure adequate strength of the cast.

• Smooth out casting material to fill in the interstices in the plaster, bond the layers together, and conform to the contour of the extremity. Use your palms rather than your fingertips to prevent the development of indentations that will predispose the patient to pressure ulcers.

• Fold back the stockinette before adding the last layer of casting material. Roll back the extra stockinette and cotton padding at the outer margins of the cast to cover the raw edges of the splinting material and create a smooth edge; secure the stockinette under the casting material.

• Hold the body part in the desired position until the cast material hardens sufficiently, typically 10 to 15 minutes.

• Check for distal neurovascular status (eg, capillary refill and distal sensation) and motor function.

• Determine recommended functional status (eg, whether patient should be bearing weight on the affected extremity).

• Arrange or recommend appropriate follow-up.

• Provide verbal and written instructions.

• Advise the patient to elevate the casted extremity above heart level whenever possible for the first 48 to 72 hours.

• Advise the patient to keep the cast clean and dry.

• Advise the patient not to insert any objects between the skin and the cast and not to cut the cast.

• Instruct the patient to watch for complications such as worsening pain, paresthesias/numbness, and/or color change distal to the cast.

• Instruct the patient to seek further care if pain cannot be controlled with oral medications at home or if the patient develops paresthesias/numbness and/or color change distal to the cast.

• Applying a cast to a swollen extremity may predispose to compartment syndrome; a splint may be used for several days until swelling subsides.

• If numbness, tingling, or a sensation of tightness develops after discharge, the patient should be instructed to seek medical care immediately.

• As swelling resolves over the week or two after casting, reduced fractures are at risk of becoming misaligned; ensure close follow-up.

• Applying cotton padding too tightly may predispose to compartment syndrome.

• Not smoothing plaster enough will keep the layers from bonding correctly, creating a weak cast.

• Improper joint positioning during immobilization can cause contractures.

• Using cooler water increases the time required for the casting material to harden, which will give the operator more time to mold the cast.

• Consider adding additional padding over bony prominences to minimize the risk of pressure sores.