Educational draft · awaiting clinical reviewThe full textbook explains uncertainty but does not replace live national or local guidance, specialist advice, or current prescribing information.
Casting, splinting and pressure complications
Musculoskeletal medicine and orthopaedics · UK scope · Sources checked 27 Aug 2026 · Clinical review pending
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A tight cast can conceal limb-threatening pressure
Escalating pain out of proportion, pain on passive stretch, new sensory or motor loss, tense swelling or worsening analgesic requirement may indicate acute compartment syndrome even when a pulse remains present.
Action: Urgently split or remove all circumferential constriction down to skin as locally trained, keep the limb at heart level, obtain immediate senior orthopaedic assessment and do not delay fasciotomy decisions for reassuring pulses or routine imaging.
Purpose and principles
Apply and monitor casts or splints that maintain alignment without sacrificing skin, nerve, perfusion or compartment safety, and respond immediately when pressure-related warning symptoms appear.
A cast or splint is a mechanical treatment with a physiological interface. It may hold a reduction, protect fixation, rest painful soft tissues or prevent contracture, but it also obscures skin and limits expansion. Choose the least restrictive device that reliably meets the treatment goal. A removable splint permits inspection and swelling but depends on correct use; a backslab accommodates early swelling; a circumferential cast offers stronger control but magnifies pressure risk. Record who made the plan and the intended position, duration and follow-up.
Inspect the entire limb before application. Identify wounds, infection, fragile skin, oedema, neuropathy, vascular disease, previous pressure injury and bony prominences. Document named nerve function, perfusion and compartment findings. Cover wounds with an accessible management plan. Apply stockinette and smooth padding without constrictive turns, adding protection at prominences and edges. Use broad palms to mould while material sets; fingertip impressions concentrate load. Avoid excessive layers and hot water because exothermic curing can burn skin.
Indications, selection and cautions
Diffuse constriction
Increasing swelling with globally tight cast, venous congestion and neurological symptoms indicates inadequate room for tissue expansion.
Focal pressure injury
Persistent local burning or pinpoint pain over a prominence may precede blister, ulcer, tendon exposure or infection.
Acute compartment syndrome
Disproportionate escalating pain and passive-stretch pain are key warnings while pulse loss is late and may never occur.
Thermal cast burn
Excess layers, hot dip water and resting a curing cast on an insulating surface can raise skin temperature dangerously.
Wet-cast maceration
Moisture trapped against skin produces itching, odour, soft white skin, microbial growth and loss of cast integrity.
Loss of mechanical control
A cast that slides, pistons or permits new deformity after oedema subsides can no longer reliably maintain reduction.
Red flags requiring action
Progressive pain despite analgesia or pain on passive stretch under a cast is acute compartment syndrome until urgently assessed.
New numbness, weakness, burning, inability to move digits, coolness, pallor or delayed capillary refill requires immediate cast and neurovascular review.
Focal persistent burning or a patient repeatedly identifying one pressure point can precede a deep cast ulcer even when the outside looks normal.
Assessment before treatment
01First-line repeated clinical and neurovascular examinationFirst stepFirst line
Why
Detect evolving compartment, nerve, perfusion, skin or fit problems before and after every cast intervention.
Interpretation and limitations
Compare with the documented baseline and contralateral limb; normal pulses do not exclude compartment syndrome.
02Immediate full skin inspection after cast removal
1Confirm indication, position, reduction, expected swelling, skin and wound access and document baseline neurovascular findings.
2Choose splint, backslab or circumferential cast according to stability and swelling, with smooth padding and protected prominences.
3Mould with broad surfaces, avoid constrictive turns and thermal risk and preserve movement of intended free joints.
4Repeat neurovascular examination, obtain required radiographs and write weight-bearing, duration and review instructions.
02Routine aftercareMonitor the hidden interfaceThe patient leaves the casting area or swelling changes during follow-up.+
1Give written and demonstrated elevation, digit movement, hygiene, wet-cast, pressure and emergency advice.
Complications, monitoring and follow-up
Repeat and document pain, passive stretch, sensation, motor function, pulse, capillary refill, colour and temperature after application and any adjustment.
Inspect cast edges, bony prominences, fit, cracks, wetness, odour and movement within the device at every contact.
Check exposed skin and encourage motion of free digits and joints to limit swelling, stiffness and tendon adhesion.
Review alignment radiographically at the fracture-specific interval and earlier after new pain, trauma or cast looseness.
For patients unable to report symptoms, schedule direct skin and fit surveillance with carers and community staff.
After pressure injury, measure wound depth, tissue viability, infection, neurological recovery and whether the replacement device remains off-loaded.
Special situations
Pulse is late reassurance
Compartment pressure can obstruct capillary perfusion while major arterial flow and a palpable distal pulse remain present.
Windows create new edges
A poorly planned cast window can allow tissue to bulge and become compressed around the opening.
Loose casts also harm
After swelling falls, sliding causes friction and loss of reduction even though the original tightness has resolved.
Neuropathy masks pressure
Absent protective sensation removes pain as an early alarm, demanding extra padding, education and scheduled inspection.
Curing generates heat
Hot water, thick layers and insulation during setting can combine to cause an avoidable thermal injury.
Common pitfalls
01
Reassuring from a palpable pulse when pain and passive-stretch findings suggest compartment syndrome.
02
Cutting only the hard shell while leaving tight padding and bandage constricting the limb.
03
Placing fingers into soft casting material and leaving focal pressure indentations.
04
Making a small window for unexplained pain without inspecting the complete skin interface.
05
Ignoring a loose cast because it no longer feels tight despite loss of reduction control.
06
Allowing a patient to insert objects beneath a cast to scratch itching skin.
Practice
Two practice questions
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Question 1 of 2
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Musculoskeletal medicine and orthopaedicsOriginal SBA
Pain under a new cast
Several hours after forearm casting, a patient has rapidly increasing pain despite opioids and pain on passive finger extension. The fingers remain warm and a radial pulse is present. What is the best immediate action?
Sources and review status4 sources · checked 27 Aug 2026 · clinical review pending+
Sources
Sources and review status
National guidance is shown before implementation-dependent detail. Apply principles in context and verify current guidance when a decision affects care. Source check completed 27 Aug 2026; clinical approval remains outstanding.
BOA National Casting StandardsCasting assessment, neurovascular documentation, application, education and pressure safety.
After application, repeat and document the complete distal examination and check the cast position, edges and intended joint control. Confirm radiographs where reduction or alignment requires them. Mark any window or split and ensure all layers are released when swelling is a concern. Teach elevation during the early swelling period without prolonged excessive elevation when compartment syndrome is suspected. Encourage movement of exposed digits and unaffected joints and explain permitted weight bearing with the exact rehabilitation wording.
Pressure complications present through changing symptoms. Diffuse tightness can impair venous return and nerve function; a focal ridge or inadequately padded prominence causes ischaemia and ulceration; a wet cast macerates skin; a loose cast rubs and loses reduction. Neuropathy or cognitive impairment may prevent reliable pain reporting, so carers and scheduled inspection become more important. Never push an object inside for itch. A cast window made without careful technique can produce oedema and pressure at its edges.
Acute compartment syndrome is a clinical emergency. Pain out of proportion and passive-stretch pain are important early findings, with paraesthesia or weakness later; pulses may remain. Remove or fully split dressings, bandages, cast and padding to skin and obtain urgent orthopaedic review. When diagnosis remains uncertain in an at-risk or unreliable patient, serial examination and compartment-pressure measurement can support the decision, but pressure measurement must not delay decompression of a convincing syndrome. Continue fracture stability and analgesia while definitive treatment proceeds.
Key points
Before application, confirm indication, reduction target, skin and wound condition, allergy, swelling trajectory and baseline motor, sensory, pulse and capillary findings.
Use an appropriate splint or backslab during evolving swelling; a circumferential cast requires enough padding, safe moulding and a plan for pressure expansion and review.
First-line post-application checks are pain, digit colour and warmth, capillary refill, pulse where relevant, named nerve motor and sensory function and ability to move uninjured joints.
Mould with broad surfaces rather than fingertips, protect bony prominences and cast edges and never insert padding, objects or instruments beneath a finished cast.
Increasing pain, passive-stretch pain or neurological change requires immediate release of every external constriction and urgent compartment-syndrome assessment; intact pulses are a late and unreliable reassurance.
Focal cast pressure requires same-day removal or windowing only under an expert plan that still permits full skin inspection and does not create a new edge-pressure point.
Give written elevation, movement, hygiene, wet-cast, skin, neurovascular and emergency return instructions and verify patient or carer understanding by teach-back.
Review reduction and fit after swelling changes; a cast can become dangerous when too tight and ineffective when too loose.
Wetness, offensive smell, fever, discharge or increasing pain can indicate skin breakdown, wound infection or a foreign object beneath the cast.
A cast that becomes loose after swelling subsides may no longer control reduction and can rub, migrate or permit displacement.
Breathlessness, chest pain or new whole-limb swelling during immobilisation requires assessment for VTE rather than attribution to the cast alone.
Interpretation and limitations
Use trends and perfusion pressure under specialist protocols; a convincing clinical syndrome proceeds to decompression without waiting for numbers.
05Targeted wound and infection assessment
Why
Evaluate discharge, odour, fever or increasing local pain beneath a cast.
Interpretation and limitations
Inspect first, then obtain cultures, blood tests or imaging only when they will direct debridement, antibiotics or fracture management.
2Arrange fracture-specific review of fit, skin, alignment and radiographs as oedema resolves.
3Replace a loose, damaged or wet device rather than accepting rubbing or loss of control.
4Increase surveillance for neuropathy, cognitive impairment, fragile skin or inability to report symptoms.
03Pressure symptomExpose and inspect the causePain, burning, odour, wetness, numbness or focal concern develops beneath the cast.+
1Assess pain trajectory, passive stretch, digit movement, sensation, perfusion and systemic features immediately.
2Remove or fully open the device sufficiently to inspect the relevant skin and relieve all constriction.
3Treat pressure wound, infection or cast failure and restore fracture control with a safely redesigned device.
4EscalationEscalate suspected deep ulcer, infection, nerve injury or threatened skin to the responsible orthopaedic team.
04Compartment emergencyRelease before irreversible ischaemiaEscalationDisproportionate escalating pain, passive-stretch pain or new neurological deficit suggests compartment syndrome.+
1Urgently split or remove every circumferential layer down to skin and keep the limb at heart level.
2Obtain immediate senior orthopaedic assessment and repeat named nerve and compartment examination.
3Use pressure measurement only for diagnostic uncertainty or unreliable examination without delaying a convincing case.
4Proceed to urgent fasciotomy when diagnosed and monitor systemic consequences and fracture stability.