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Immobilisation - Thumb spica backslab

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Fractures of scaphoid (or suspected fracture)

Fractures of first metacarpal or phalanx

Ulna or radial collateral ligament injuries of thumb

Contraindications (absolute in bold)



Open reduction with internal fixation

Informed consent

Verbal consent

Less complex non-emergency procedure with low risk of complications

Potential complications

Failure (reduction or immobilisation)

Thermal burns (from heat released during setting of plaster)

Neurovascular compromise



Abrasions and pressure sores (with risk of infection)

Joint stiffness

Procedural hygiene

Standard precautions

PPE: non-sterile gloves, apron


Plaster room or bed space


Procedural clinician


Stockinette (optional) - small size for thumb, 7.5cm for hand or forearm

7.5cm cotton padding (slightly narrower than arm diameter)

10cm plaster for backslab (slightly wider than arm diameter)

Trauma scissors

Bowl of cold water

Crepe bandages



Sitting with elbow supported on table

Elbow: flexed at 90 degrees

Forearm: neutral pronation and supination

Wrist: 20 degrees extension

Thumb: opposition towards middle finger, interphalangeal joint neutral (if included in backslab)


Estimate plaster length by laying dry splint next to the area to be splinted

Layers: 8-10 layers

Distal margins: distal palmar crease and below IPJ thumb (beyond tip of thumb for phalangeal fractures)

Proximal margins: three finger-widths below elbow crease

Cut out corners out of backslab at distal end


Consider paracetamol 1g, ibuprofen 400mg and oxycodone 5mg (pain relief one hour pre-procedure)

Consider fentanyl 25-50mcg IV (pain relief pre-procedure adjusted to co-morbid status)

Consider fentanyl 100mcg IV (1.5mcg/kg pain relief pre-procedure adjusted to co-morbid status)


Ensure adequate analgesia prior to procedure

Inspect the extremity prior before splinting, document lesions repairing or dressing as normal

Apply stockinette to arm beyond margins of plaster (allowing folded to a smooth edge)

Cut a small hole on stockinette for thumb

Apply small stockinette to thumb beyond margins of plaster (allowing folded to a smooth edge)

Apply 2-3 layers of cotton padding beyond plaster margins

Tearing or cutting padding as it passes through the first webspace

Ensure bony prominences are well padded and cotton padding overlaps itself by 25 - 50% with minimal creases

Submerge the pre-prepared dry backslab in water until bubbling stops, then remove

Squeeze out excess water, smooth and apply over radial aspect of forearm and thumb

Turn back padding around the distal and proximal margins of the plaster

Apply crepe bandage firmly over slab and fasten with tape

Gently mould plaster to patient anatomy maintaining POSI position until hardened

Post-procedure care

Check X-ray, circulation and limb function:

Confirm fracture reduction with post-procedure X-ray

Check capillary refill and comfort (loosen crepe bandage or re-splint if required)

Confirm full MCP flexion and extension through digits 2-5

Confirm full flexion and extension of interphalangeal join of the thumb (if not included in plaster)

Confirm full opposition of thumb to at least middle finger

Confirm full elbow flexion

Provide plaster care instructions:

Elevate limb when possible using a collar and cuff sling (decreases pain and swelling)

Avoid applying pressure and heat to the cast

Do not wet the plaster (use plastic bag to protect plaster while in shower)

Return for assessment if damaged cast, increasing pain, numbness or skin colour changes

Provide temporary cast plaster care patient fact sheet


Temporary casting of open fractures requires covering open wounds with saline-moistened sterile gauze

Always use clean cold water (avoiding thermal injury and allowing for 10 minutes moulding time)

Extra padding at bony prominences avoids pressure areas (radial and ulnar styloid)

All backslabs are temporary requiring definitive management after two weeks (e.g. full cast)


There are a variety of splinting techniques in common emergency department practice. Indications for specific casts and recommended methods of application may vary depending on your institution. If in doubt seek local advice from an experienced provider or discuss with your orthopaedic team.

Peer review

This guideline has been reviewed and approved by the following expert groups:

Emergency Care Institute

Please direct feedback for this procedure to


NSW Agency for Clinical Innovation. Orthopaedic/musculoskeletal. Sydney: ACI; 2020. Available from

Roberts JR, Custalow CB, Thomsen TW. Roberts and Hedges’ clinical procedures in emergency medicine and acute care. 7th ed. Philadelphia, PA: Elsevier; 2019.

Dunn RJ, Borland M, O’Brien D (eds.). The emergency medicine manual. Online ed. Tennyson, SA: Venom Publishing; 2019.

Eiff MP, Hatch R. Fracture management for primary care. 3rd ed. Philadelphia PA: Saunders; 2011.

Stracciolini A. Basic techniques for splinting of musculoskeletal injuries In: UpToDate. Waltham (MA): UpToDate. 2019 April 18. Available from:

Liverpool hospital emergency department: Plaster booklet (2019)

© Agency for Clinical Innovation 2021