Plaster of Paris (POP) Application

Objective

To guide the correct application, management, and complication prevention of Plaster of Paris (POP) casts for patients requiring temporary immobilisation of limbs.

 

Scope

This guideline includes step-by-step instructions for the correct application of a POP backslab, including:

  1. Indications
  2. Contraindications
  3. Required materials
  4. Application technique
  5. Post-application care
  6. Complication management

This guideline does not cover definitive fracture management, which is addressed in other guidelines.

Note that this guidance is limited to the application of a slab cast. Circumferential casts are generally avoided in early fracture management and should never be applied forwards of deployed hospital care.

 

Audience

For registered healthcare professionals working in forward medical locations or Emergency Departments on deployed operations.

 

Indications

  • Suspected or confirmed fractures requiring temporary immobilisation
  • Severe soft tissue injuries requiring immobilisation
  • Post-operative protection of surgical sites
  • Open fractures requiring stabilisation until definitive care can be delivered

Contraindications include suspected compartment syndrome.

In the forward environment, it may be possible to achieve effective immobilisation more easily using a mouldable splint such as a SAM splint.

 

Preparation

Materials Required:

  • Plaster of Paris bandages
    • Upper limb (forearm backslab): ~6–8 layers of 7.5 cm or 10 cm POP bandage
    • Lower limb (below-knee backslab): ~10–12 layers of 10 cm or 15 cm POP bandage
    • Full leg (above-knee backslab): ~12–15 layers of 15 cm POP bandage
  • Stockinette and padding (orthopaedic wool). Choose a width that fits comfortably around the limb without excessive tightness. Do not use Tubigrip®
    • Upper limb:5–7.5 cm width, cut to extend ~5 cm beyond slab ends
    • Lower limb:5–10 cm width, cut to extend ~5 cm beyond slab ends
  • Bucket of water
  • Bandage shears/scissors
  • Gloves
  • Elastic bandage for securing

Patient Preparation:

  • Explain the procedure to the patient
  • Ensure adequate analgesia before attempting plaster application
  • Document neurovascular status before application
  • Position the limb appropriately (e.g. ankle at 90° for lower limb injuries)

 

Procedure

This is a summary; see full detail in the accordion sections below.

  1. Apply Stockinette at least 5cm beyond the intended slab length for protection.
  2. Apply Padding: Wrap evenly, ensuring extra layers over bony prominences.
  3. Prepare POP Bandage: Measure then immerse in water and gently squeeze out excess
  4. Apply the POP Slab: Position along the posterior of limb and mould to shape
  5. Secure with Bandage: Ensure proper limb positioning during setting.
  6. Allow plaster to set until hardened
  7. Monitor for Neurovascular Compromise: Check circulation, movement, and sensation.

 

Post-Procedure Care:

  • Reassess & document circulation, motor function, and sensation within the first hour
  • Allow plaster to set fully. Do not weight bear as this is a temporary cast. 
  • If compartment syndrome is suspected (severe pain, tense limb, paraesthesia, pallor), first release any circumferential dressing, and if symptoms do not ease then remove the cast to ensure there is no restriction to limb swelling. Consult the CGO on Compartment Syndrome (link to follow) and seek orthopaedic advice.

 

Prolonged Casualty Care

If prompt evacuation is not possible then:

  • Monitor for pressure damage and swelling from setting plaster. In extremely rare cases it can cause thermal burns.
  • Elevate the limb to reduce swelling.
  • Reinforce or replace slabs as needed to maintain immobilisation.
  • Administer analgesia as per analgesia guidelines (link to follow).

 

Paediatric Considerations

  • Use additional padding to accommodate swelling.
  • Adjust slab length and positioning to prevent joint stiffness.

Detailed Procedure

Procedure

  1. Apply Stockinette:
    • Select an appropriate width (5–10 cm for upper limbs, 7.5–15 cm for lower limbs).
    • Cut a length that extends at least 5 cm beyond both ends of the intended backslab.
    • Smooth the stockinette over the limb to prevent wrinkles, which could cause pressure sores.
    • Do not use Tubigrip® or similar products as these are not suitable for this purpose.
  2. Apply Padding (Orthopaedic Wool):
    • Upper limb: Olecranon, ulnar styloid, radial styloid.
    • Lower limb: Malleoli, tibial crest, patella, heel.
    • Wrap evenly around the limb with a slight overlap (~50%) between layers.
    • Ensure extra padding over bony prominences, such as:
    • Leave padding slightly extended at the edges to cushion the slab’s ends.
  3. Prepare Plaster of Paris Bandage:
    • Fill a bucket with room-temperature water (avoid hot water, which increases exothermic heat release).
    • Measure the plaster length to the patient's limb, then layer the dry plaster back and forth until sufficient layers achieved.
    • Immerse the POP bandage in water for 5–10 seconds, allowing bubbles to dissipate.
    • Gently squeeze out excess water without wringing, maintaining a smooth roll.
  4. Apply the POP Slab:
    • Forearm fractures: Elbow at 90°, wrist slightly extended (10–20° dorsiflexion). If applying for a wrist fracture do not let the POP cross the elbow joint line.
    • Lower leg fractures: Ankle at 90° (neutral position). If applying for a lower leg fracture do not let the POP cross the knee joint line.
    • Position the patient’s limb in the desired functional position:
    • Place the pre-measured POP slab along the posterior aspect of the limb (or along the ulnar border for forearm injuries).
    • Gently mould the slab to the natural contour of the limb using the palms (avoid fingertips to prevent pressure points).
  5. Secure with an Elastic Bandage:
    • Wrap evenly and snugly, avoiding excessive tightness that could cause circulatory compromise.
    • Ensure stockinette and padding remain visible at both ends of the backslab.
  6. Allow Plaster to Set:
    • POP typically sets within 10–15 minutes but remains vulnerable to deformation for 24 hours.
    • Advise no weight-bearing until fully dry (if applicable).
  7. Monitor for Neurovascular Compromise:
    • Check capillary refill, pulses, sensation, and motor function immediately after application.
    • Reassess every 15 minutes for the first hour, then hourly as needed.

Complications

  • Skin Irritation and Breakdown: Ensure adequate padding and avoid excessive moisture.
  • Thermal Burns: Prevent excessive wetting of plaster and avoid prolonged direct skin contact.
  • Circulatory Impairment: Conduct regular neurovascular checks; split the slab if required.
  • Plaster Breakage or Weakness: Reinforce with additional layers or replace if compromised.

Neuromuscular Assessment

Circulation

  • Capillary Refill Time (CRT): Press on a distal digit (finger or toe) and release. Normal refill time is ≤2 seconds.
  • Skin Colour and Temperature: Compare to the unaffected limb (pale, cool skin may indicate impaired circulation).
  • Peripheral Pulses: Palpate distal pulses (radial, dorsalis pedis & posterior tibial). May require the use of a Doppler if pulses are weak or absent.

Motor Function (Active Movement):

  • Ask the patient to move their fingers or toes.
  • Assess muscle strength and compare to the unaffected side.
  • Look for weakness or paralysis, which may indicate nerve compression.

Sensation (Peripheral Nerve Function):

  • Look for numbness, tingling (paraesthesia), or loss of sensation.

Last reviewed: 27/01/2026

Next review date: 27/01/2027