Compartment syndrome

Overview

•Pressure rises within a closed fascial compartment → venous compression first → oedema → arteriolar ischaemia → self-amplifying cycle

•Most common cause: tibial shaft fracture; most commonly affects the lower leg (4 compartments) and forearm

•Most common in males under 35; without associated fracture → higher risk of delayed diagnosis

Presentation

•Pain disproportionate to injury - deep, burning, poorly localised; refractory to opioid analgesia - earliest and most sensitive sign

•Pain on passive stretch - passively extending toes/fingers sharply worsens pain; key early diagnostic manoeuvre

•Tense, woody swelling - compartment feels hard on palpation

•Paraesthesia - tingling/numbness in nerve distribution traversing the compartment (e.g. first/second toe web space = deep peroneal nerve) - the ONE early 'P'

•Paralysis - late, grave sign indicating advanced ischaemia

•Pallor, pulselessness, coolness - very late, often indicate irreversible damage already present

⚠️

Pulses remain palpable until very late - arterial flow ceases only when compartment pressure approaches systolic BP. A patient with acute compartment syndrome will almost always have palpable pulses. Waiting for pulselessness before acting causes permanent injury.

Investigations

•Acute compartment syndrome is a clinical diagnosis - investigations must never delay surgical intervention

•Compartment pressure measurement - normal 0-8 mmHg; 20-30 mmHg = high risk, monitor closely; ≥40 mmHg = surgical threshold

•Delta pressure = diastolic BP minus compartment pressure; <30 mmHg = indication for fasciotomy even if absolute pressure <40 mmHg

•Serum CK - elevated = muscle cell lysis; monitor for rhabdomyolysis

•Renal function and urinalysis - assess for myoglobinuria and AKI

•Plain X-ray - identify underlying fracture

💡

Delta pressure is especially important in hypotensive patients - a compartment pressure of 30 mmHg may represent critical ischaemia if diastolic BP is low.

Management

•Acute compartment syndrome: immediate orthopaedic referral and emergency four-compartment fasciotomy - irreversible muscle necrosis begins within hours

•Chronic exertional compartment syndrome: first-line = activity modification and physiotherapy; fasciotomy if symptoms persist and patient cannot modify exercise load

Complications

•Rhabdomyolysis - myoglobin release → nephrotoxic, precipitates in renal tubules → AKI; severe cases cause hyperkalaemia and cardiac arrhythmias

•Volkmann ischaemic contracture - forearm muscle fibrosis → fixed flexion deformity of wrist and fingers; classically after supracondylar fracture in children

•Permanent nerve injury - most commonly deep peroneal nerve (foot drop) or posterior tibial nerve

•Limb amputation - if extensive muscle necrosis not amenable to salvage

•AKI and death - from severe rhabdomyolysis and multiorgan failure