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How To Apply a Short Arm Cast

By

James Y. McCue

, MD, University of California San Francisco - Fresno

Last full review/revision Jun 2021| Content last modified Jun 2021
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A short arm cast extends from the distal palmar crease to the proximal third of the forearm and is intended to immobilize the wrist and distal forearm.

Indications

  • Certain carpal bone fractures and/or dislocations (eg, lunate/perilunate dislocation, pisiform fracture)

  • Second to fifth metacarpal fractures

Contraindications

  • Proximal or mid-forearm fractures (these require immobilization to include the elbow)

  • Injuries that may continue to swell after application of the cast

  • Fractures that require operative care and should be temporarily immobilized with a splint

Complications

Equipment

  • Stockinette

  • Roll padding

  • Plaster or fiberglass casting material*, 7.5- to 10-cm (3- to 4-inch) width

  • 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.

Positioning

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

  • The patient is seated with the elbow supported on a firm, flat surface.

  • The elbow should be held in 90° flexion during casting.

  • The wrist should be immobilized in the neutral position (about 20° extension).

Step-by-Step Description of Procedure

  • Apply stockinette to cover the area (eg, about 5 to 10 cm) proximal and distal to the area to which the cast will be applied. When finished, the cast should cover the area from just proximal to the metacarpophalangeal joints at the distal palmar crease to about the junction of the middle and proximal thirds of the forearm.

  • Place 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.

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

  • Consider adding padding over bony prominences.

  • Immerse the casting material in lukewarm water.

  • Gently squeeze (do not wring out) excess water from the casting material.

  • Apply the casting material circumferentially from just proximal to the metacarpophalangeal joints to the distal third of the forearm, overlapping the underlying layer by half the width of the casting material. Leave about 2.5 cm (1 inch) of the padding and stockinette from the end of the casting material.

  • Place 4 to 6 layers of plaster (typically) to ensure adequate immobilization. Each layer overlaps by half the width; this requires 2 to 3 passes circumferentially.

  • For fiberglass, 2 to 4 layers is usually adequate (follow product-specific instructions for application).

  • Smooth out casting material to fill in the interstices in the plaster and conform to the contour of the arm. 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.

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

  • Maintain the wrist in the neutral position until the casting material hardens sufficiently, typically 10 to 15 minutes.

Aftercare

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

  • Arrange or recommend appropriate follow-up.

  • Provide verbal and written instructions.

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

  • Advise patients 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 color change to the fingers.

  • Instruct the patient to seek further care if pain cannot be controlled with oral drugs at home.

Warnings and Common Errors

Tips and Tricks

  • The metacarpophalangeal joints should remain free.

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