Compartment Syndrome in the CST Interview
How to answer a compartment syndrome scenario in the CST interview: pain out of proportion, splitting the cast at the bedside, and escalating for fasciotomy.
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Escalating leg pain despite morphine in a man with a tibial fracture is the CST scenario that rewards decisiveness at the bedside: the examiner wants to hear what your own hands do in the next five minutes, not a referral letter.
How the scenario tends to open
A typical stem: a young cyclist with a closed tibial fracture in a backslab, awaiting nailing on tomorrow’s list, whose pain has become unbearable over two hours despite regular strong analgesia. Uncontrolled, escalating pain after a tibial fracture is compartment syndrome until proven otherwise.
The approach that scores
Attend immediately and act at the bedside before anything else: take the backslab and every constricting layer down to bare skin, and keep the limb at heart level — not raised above it, because extra elevation drops perfusion pressure in a compartment that is already struggling.
Then make the diagnosis clinically: pain far beyond what the injury explains, made worse by passively stretching the muscles of the compartment, with tense swelling and altered sensation. Document neurovascular status, and say the sentence examiners listen for: pulses usually remain palpable — losing them is a late sign, and waiting for it costs muscle.
- State that compartment syndrome is a clinical diagnosis; pressure monitors have a role only when the patient cannot report pain — unconscious or otherwise unassessable — and must never hold up surgery.
- Escalate immediately to the orthopaedic registrar and consultant: the only definitive treatment is fasciotomy, done as an emergency, because muscle starts dying within hours.
- Prepare for theatre in parallel: nil by mouth, IV access and fluids, bloods including group and save, anaesthetist and theatre coordinator alerted so the case is not queued behind routine work.
- Anticipate rhabdomyolysis after a large muscle injury: fluids, creatine kinase and renal monitoring, urine output.
Where candidates lose marks
Reaching for investigations to "confirm" the diagnosis is the recurring failure — as is reassuring the nurses over the phone and reviewing in the morning, which in real cases is how limbs are lost and negligence claims are made. Meticulous, timed documentation belongs in your answer for exactly that reason.
Rehearse it
Reading about compartment syndrome is the easy half. Rehearse this exact scenario out loud, on the clock, with an AI examiner — this scenario is in Reviva’s library, with feedback marked the way the panel marks. Or start with the wider format in the cst clinical scenarios guide.
Frequently asked questions
- What are the earliest signs of compartment syndrome?
- Pain out of proportion to the injury, made worse when the compartment’s muscles are passively stretched, with tense swelling. Sensory change comes next; loss of pulses is a late, pre-terminal sign for the limb.
- Do you measure compartment pressures before fasciotomy?
- Not in an awake patient who can report pain — the diagnosis is clinical, and pressure monitoring belongs to the unconscious or unassessable. Nothing should delay definitive fasciotomy.
- Why is the limb kept at heart level rather than elevated?
- Elevation above the heart lowers arterial perfusion pressure into a compartment that is already ischaemic. Heart level balances swelling against perfusion.
Sources. Grounded in the standard emergency management of acute compartment syndrome as rehearsed in Reviva’s CST clinical scenario. Educational only — follow your local policies and current national guidance.