Splints and the plaster backslab

What it is

A splint immobilises an injured limb to reduce pain, protect soft tissue and hold a fracture or reduced dislocation in place. Unlike a cast it does not go all the way around the limb, so it allows for the swelling of the first days, which is why splints are preferred for acute injuries and casts come later. A backslab is a splint made of layers of plaster of Paris (or fibreglass) laid along one side of the limb over padding and held with a bandage. Common examples are the forearm backslab for a distal radius fracture, the thumb spica for a suspected scaphoid fracture, the ulnar gutter for a fifth metacarpal (boxer's) fracture and the posterior ankle splint, often with a stirrup, for ankle fractures. The joints above and below are usually included, and the limb is held in a position of function. Plaster gives off heat as it sets, so too many layers or hot water can burn. Above all, neurovascular status is checked and recorded before and after the splint, because a splint can hide or cause compartment syndrome.

Indications

• Fractures, as temporary immobilisation before review or definitive treatment, or as definitive treatment for some.
• After reduction of a fracture or dislocation, to hold the position.
• Severe sprains, tendon and ligament injuries and some soft-tissue injuries, for pain relief and protection.
• Acute injuries where swelling is expected: a splint allows it, a circumferential cast does not.

Contraindications and precautions

• Check and record pulses, capillary refill, sensation and movement before splinting; a deficit needs urgent senior review.
• Suspected compartment syndrome (pain out of proportion, pain on passive stretch) is an emergency, not a splinting job.
• Open fractures need wound care, antibiotics and orthopaedic referral; splinting is only one part of their care.
• Inspect the skin: wounds, blisters and pressure-prone areas need padding and documentation.
• Thin skin, poor sensation (diabetes, neuropathy) and children need extra padding and closer checks.

Equipment

• Stockinette and cotton padding (cast padding).
• Plaster of Paris or fibreglass splint material.
• A bucket of cool to lukewarm water (not hot) and gloves.
• Elastic or crepe bandage, tape, scissors and a sling or crutches as needed.
• Analgesia, and a means to record neurovascular status before and after.

Step by step (and why)

1. Explain, give analgesia and check and record neurovascular status and the skin — this is the baseline for later checks.
2. Measure the plaster on the uninjured limb — measuring on the injured side hurts and gives the wrong length.
3. Apply stockinette and padding, with extra over bony prominences — padding prevents pressure sores.
4. Dip the plaster briefly in cool to lukewarm water and squeeze out the excess — hot water speeds setting and raises burn risk.
5. Smooth the layers together and lay them over the padding, folding the padding edges back — plaster must not touch skin.
6. Wrap the bandage firmly but not tight, distal to proximal — a tight bandage turns the splint into a cast.
7. Mould with the flats of the palms, not the fingertips, and hold the position of function — fingertips make pressure points.
8. Hold still until set and keep the limb off pillows meanwhile — pillows trap heat from the setting plaster.
9. Recheck and record neurovascular status, and get imaging after any reduction — a splint can cause or hide compromise.
10. Give a sling or crutches, elevation advice and written warning signs — early return prevents compartment syndrome harm.

Positions of function; the fracture pattern and local protocol decide the details.

Complications

• Compartment syndrome and neurovascular compromise from swelling under a tight splint or bandage.
• Pressure sores and skin breakdown from poor padding or fingertip indentations.
• Thermal burns from setting plaster (too many layers, hot water, limb on a pillow).
• Loss of reduction or malposition from poor moulding or the wrong position.
• Joint stiffness and muscle wasting; venous thrombosis with lower limb immobilisation in at-risk patients.
• Dermatitis or infection under a wet or soiled splint.

Next step

• Elevate the limb above heart level and move the free joints (fingers or toes) often.
• Return at once for increasing pain, numbness, tingling, pale, blue or cold fingers or toes, or a splint that feels too tight: loosen the bandage on the way.
• Keep the splint dry and do not push objects inside it.
• Arrange fracture clinic or orthopaedic follow-up and repeat imaging as needed.
• Call orthopaedics at once for neurovascular deficit, open fracture, suspected compartment syndrome or a failed reduction.

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Elsewhere in DurgiPedia

• Fractures and fracture healing
• Complications of immobility and how to prevent them

Connections

← All clinical skills

Educational content; it does not replace supervised hands-on training, your institution's protocols or a prescriber's order. A procedure is learnt with a teacher and done only once you are trained to do it.

Sources: Splinting (StatPearls (NCBI Bookshelf), 2023); Wrist Splint (StatPearls (NCBI Bookshelf), 2023).

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Representative model, for educational purposes only.