Immobilisation - POSI backslab

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Fractures of metacarpal or phalangeal digits 2-5

Dislocation of metacarpal or phalangeal digits 2-5 (post reduction)

Flexor and extensor tendon injuries (open or closed)

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 pressures 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)

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, forearm in supination

Wrist supported in slight extension with dorsal plaster roll

Wrist in 20-30 degrees extension

MCP in 70-90 degrees flexion

IP joints in full extension


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

Layers: 8-10 layers

Distal margin: beyond fingertips

Proximal margin: two finger-widths below elbow crease

Cut a semicircle out of the plaster backslab for the thenar eminence

Cut distal corners off plaster to improve shape and moulding around fingers


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 IN (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 2-3 layers of cotton padding beyond plaster margins

Tearing or cut padding as it passes through the first webspace

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

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

Squeeze out excess water, smooth and apply onto volar aspect of forearm, hand and to beyond fingertips

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 position of safe immobilisation 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)

Check POSI position maintained (wrist 20-30 degrees extension, MCP 70-90 degrees, IP joints 0 degrees)

Check full elbow flexion and thumb flexion and extension (without webspace irritation)

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