# Plaster Cast Application

## Overview

This module describes how to apply a definitive circumferential cast to immobilise a fracture.

## Indications

1. Fractures (usually post-acute, after swelling has subsided)

2. Some soft tissue injuries such as severe sprains

3. Dislocations after reduction

4. Some congenital deformities

## Contraindications

1. Injuries with a high risk of swelling

2. Open fractures or limbs with open wounds

3. Insensate limbs

## Patient information and consent

Always verify your patient’s identity and obtain informed consent before proceeding.

### How do I explain this procedure?

“This broken bone will need to stay completely still for a few weeks to heal. I’m going to make a plaster cast for it that will keep it from moving while it is healing.”

### What can my patient expect?

“I’m going to wrap a few layers of bandages around your limb, then put on some layers of plaster that will harden within a few minutes. The cast may feel warm as it hardens. It will take a day to be fully hardened.”

### What is my patient’s role?

“Let me know if you feel any areas where the cast is pressing against you too hard, or where it feels uncomfortable or painful. While the cast is still hardening today, try not to move your limb around too much. Come back to the clinic tomorrow for a cast check, and after x weeks, come back again so we can remove the cast. Don’t let your cast get wet or dirty. You can wrap it in a plastic bag during showering. Don’t insert objects into the cast, such as a ruler to scratch itchiness.”

## Preparation

X-rays should be taken before casting, and the degree of displacement should be assessed.

Undisplaced or minimally displaced fractures usually do not require reduction. Displaced fractures need to be

reduced

reduced

Reduction is usually accomplished by longitudinal traction, followed by exaggerating the displacement, followed by three-point pressure to reduce the displacement. Ensure adequate analgesia or conscious sedation while performing the reduction.

first.

Prepare a trolley with equipment. An assistant may be helpful in holding the reduced fracture in place and supporting the limb.

### Documentation

1. Patient notes

### Equipment

1. Alcohol-based hand rub

2. Non-sterile gloves

3. Plastic apron

4. Orthopaedic padding (OrthoWool)

5. Stockinette

6. Scissors

7. Plaster of Paris (generally broader rolls for lower limbs and narrower for upper limbs; 3-4 rolls)

8. Bucket of lukewarm water

## Site & Positioning

The type of fracture dictates the position in which a limb is immobilised. For choice of cast, see Cast/Backslab Choice.

Thumb spica cast: forearm in neutral position, wrist in 25° extension, thumb in position of function (holding a can). Apply the cast ​​from the proximal one third of the forearm to just distal to the interphalangeal joint of the thumb.

Below elbow cast: forearm in neutral position, wrist neutral or slightly flexed. The cast is applied from the proximal forearm to the proximal palmar crease.

Above elbow cast: forearm in neutral position, elbow bent 90°, wrist neutral or slightly flexed. The cast is applied from the proximal upper arm, just beneath the axilla, to the proximal palmar crease.

Below knee cast: ankle in neutral. Avoid plantar flexion. The cast is applied from just proximal to the toes to just below the knee. Make sure that it is low enough for the knee to flex to 90°.

Above knee cast: ankle in neutral, knee slightly flexed. Avoid plantar flexion. The cast is applied from just below the greater trochanter to just proximal to the toes.

## Procedure

Follow medical asepsis with non-sterile gloves.

1. Perform hand hygiene. Don nonsterile gloves & plastic apron.

2. Examine the injured limb
   Examine the injured limb

   Look for colour and capillary refill, feel for temperature and sensation, and ask the patient to move the limb.

   and document the results.

3. Under analgesia, reduce the fracture if required.

4. Cover the injured limb with stockinette, leaving enough to fold over the ends on either side.

5. Wrap the limb in orthopaedic padding. Start and end with a double wrap. As you advance up the limb, make a 50% overlap of each wrap. Around joints, use a figure-8 technique to reduce bulk.

6. Immerse a roll of plaster of Paris in the water until it stops bubbling. Lift it out and drain away excess water.

7. Wrap the plaster around the limb, starting distally and working proximally, making a 50% overlap of each wrap. Wrap without putting tension on the plaster. If leaving the thumb free, pinch or cut the plaster to allow room in the crease of the thumb. If leaving the fingers free, allow enough room for the metacarpophalangeal joints to flex. Leave toes exposed.

8. Once you reach the proximal limit of the cast, wrap the plaster in the distal direction using the same technique. Wet and wrap a second roll of plaster to strengthen the cast. Wipe up and down the cast with wet palms to weld the layers.

9. Fold down the edges of stockinette to form smooth edges. Apply a last layer of plaster, catching the edges of the stockinette, to complete the cast.

10. Rub up and down the cast with wet palms. Use your palms to mould the cast into an oval shape. Mould the cast around the injury to create a three-point fixation.

11. Hold the limb in position for 5 minutes until the cast is set.

12. Examine the injured limb

    again
    again

    Look for colour and capillary refill, feel for temperature and sensation, and ask the patient to move the limb.

    and document the results.

13. Dispose of medical waste safely.

14. Record completion of the procedure in patient notes.

## Troubleshooting

My patient came back complaining of pain inside the cast.

Severe pain, especially pain on passive stretching of the limb, could be a sign of developing

compartment syndrome

compartment syndrome

Signs and symptoms of compartment syndrome include severe pain, pain with passive stretching, poikilothermia, paraesthesia, pulselessness, pallor, and paralysis.

. If a patient complains of pain, split the cast on 2 sides (bivalve), including the padding and stockinette. If splitting the cast resolves the problem, a firm bandage is wrapped around the split cast to keep the fracture immobilised. The cast can be completed in 5-7 days once swelling has resolved. If the symptoms do not resolve, remove the cast completely and evaluate for compartment syndrome.

My patient is complaining of a burning sensation inside the cast.

Pressure ulcers can develop within hours in poorly fitted casts. Remove the cast and assess for cast sores. Re-immobilise with a cast with a window cut out of it over the affected area, or with a backslab.

## Risks

1. Pressure ulcers & infected wounds under the cast

2. Compartment syndrome

3. Malunion or failure to heal

4. Iatrogenic fractures during reduction

5. Nerve damage

6. Muscle atrophy

7. Complex regional pain syndrome

8. Arthritis

## References

1. Boyd AS, Benjamin HJ, Asplund C. Splints and Casts: Indications and Methods. Am Fam Physician. 2009 Sep 1;80(5):491-499. Available from: https://www.aafp.org/afp/2009/0901/p491.html

2. Kruger N, Venter P. Plaster of Paris casts. In: Held M, editor. Orthopaedics for Primary Health Care. Available from: https://vula.uct.ac.za/access/content/group/1b893abf-7d9f-43e3-aebc-745161173a9e/Skills/51_Plaster%20application%20-%20final.pdf

3. Vermaak S. How to Apply a Plaster Cast. In: Mash B, Blitz-Lindeque J, eds. South African Family Practice Manual. 2nd ed. Pretoria: Van Schaik Publishers; 2010: 347-348.