Acute Compartment Syndrome

A surgical emergency, not a complication to note in passing. Missing it or recognising it late costs muscle, nerve and sometimes the limb. This page is about recognising it early enough to act — definitive management is fasciotomy, which happens after urgent transfer, not in the urgent-care room.

Who’s at risk

Three-quarters of cases follow a fracture. Tibial shaft fractures are the single most common cause, followed by distal radius fractures; in children, supracondylar humeral fractures and both-bone forearm fractures carry the same risk. Compartment syndrome can also follow a crush injury, a tight cast or circumferential dressing, a vascular injury, a burn, or reperfusion after a period of ischaemia — and it can occur without any fracture at all. The leg’s anterior compartment is the single most common site, but the forearm, thigh, hand and foot are all recognised locations.

Recognition — get in before the late signs

Pain out of proportion to the injury is the earliest and most reliable sign, often before there is anything to see. Pain on passive stretch of the muscles running through the compartment (for a leg: passive dorsiflexion or plantarflexion of the toes/ankle) is an early, sensitive finding — check it specifically, don’t wait for it to be volunteered. An escalating analgesia requirement in a patient who should be settling is another early clue. On palpation the compartment itself feels tense or “wood-like”.

Pain is difficult to assess in a polytrauma patient and impossible to assess once a patient is sedated, and it is unreliable in a young child who cannot verbalise — for those three groups, the findings that do not depend on pain take on more weight.

The classic “five/six P’s” — pulselessness, paralysis, pallor, plus pain, paraesthesia and poikilothermia — are late findings, and by the time most of them appear irreversible damage has often already started. A palpable distal pulse does not exclude compartment syndrome — a pulse can remain present even in a severely compromised limb, and its presence or absence does not reliably reflect the tissue pressure inside the compartment. Do not use pulse presence to reassure yourself or the patient.

Onset is usually within a few hours of the injury but can be delayed up to 48 hours, so a single normal check at presentation does not clear the patient — any at-risk fracture needs planned reassessment, not a one-off.

What to do

• Remove anything circumferential — cast, split cast, dressing or bandage — immediately; this alone can meaningfully drop compartment pressure.
• Keep the limb at heart level to prevent hypoperfusion. Do not elevate it above the heart the way standard limb-injury first aid would suggest — for a compartment at risk, elevation worsens perfusion rather than helping it, and this is worth saying explicitly to whoever is looking after the patient.
• Do not rely on ice or further tight bandaging for pain control — they add to the compartment pressure problem rather than solving it.
• Analgesia should not be withheld to “keep the pain sign visible” — treat pain adequately, but treat it as a vital sign that needs reassessing, not switched off and forgotten.
• Arrange urgent transfer for surgical review the moment compartment syndrome is suspected clinically — a normal single pressure reading does not exclude it, and definitive treatment (fasciotomy) is time-critical, not something to defer pending further certainty in a setting without surgical capability. Where the clinical picture is genuinely inconclusive, needle compartment pressures can settle the question and are relied on in particular for a sedated or obtunded patient. Unequivocally positive clinical findings, however, should bypass measurement altogether and proceed straight to operative decompression.
• When pressure is checked, a delta-P — compartment pressure within about 30 mm Hg of the diastolic blood pressure — supports the diagnosis. The measurement should be taken near the fracture, within 5 cm of the injury site.

Why the urgency

Outcome depends on how quickly the compartment is decompressed. Fasciotomy within six hours of onset gives close to full recovery of limb function; delay to 12 hours leaves only about two-thirds of patients with normal function; delay beyond that risks permanent nerve damage, Volkmann’s contracture, chronic pain, and in the worst cases amputation. This is the reason a suspected case cannot wait for the next scheduled review — every hour of delay measurably worsens the outcome.