Compartment Syndrome — Diagnosis and Management

Acute compartment syndrome (ACS) is a surgical emergency in which elevated pressure within a closed fascial compartment compromises perfusion to the muscles and nerves within that compartment, leading to ischaemia, necrosis, and potentially permanent functional loss. If not recognised and treated within 6–8 hours, the consequences are devastating — Volkmann`s ischaemic contracture, permanent nerve damage, and in severe cases, limb loss and life-threatening rhabdomyolysis. The diagnosis must be made clinically in the conscious patient; the threshold for measurement and treatment must be low in any at-risk patient.

• Pathophysiology — the compartment pressure cycle: as compartment pressure rises (from haematoma, oedema, reperfusion injury, tight cast), capillary perfusion pressure is overcome; the critical threshold at which perfusion ceases is when the compartment pressure approaches the diastolic blood pressure; arteriolar flow ceases when the arteriole-venule pressure gradient becomes insufficient; the result is progressive ischaemia of muscle and nerve within the compartment; ischaemia causes further oedema (cell membrane failure, fluid leak) which further raises compartment pressure — a vicious cycle; without fasciotomy to decompress the compartment, this cycle is irreversible
• Compartment pressure thresholds: absolute pressure >30 mmHg is widely cited as the threshold for fasciotomy; however, the more physiologically accurate threshold is the delta P = diastolic blood pressure minus compartment pressure; delta P <30 mmHg = indication for fasciotomy; this accounts for the patient`s individual haemodynamic status — a hypotensive patient (diastolic BP 40 mmHg) will develop compartment syndrome at a lower absolute compartment pressure than a normotensive patient (diastolic 80 mmHg); always calculate delta P in addition to absolute pressure
• Causes: trauma (fractures — tibial shaft fracture is the most common cause; radius/ulna fractures — compartment syndrome of the forearm; supracondylar fracture of the humerus — Volkmann`s in children); reperfusion injury (after arterial repair or revascularisation); prolonged limb compression (crush injury; post-surgical positioning); burns; coagulopathy/anticoagulation; tight circumferential dressings or casts; excessive fluid resuscitation

• The 6 Ps of compartment syndrome: (1) Pain — the earliest and most sensitive symptom; pain out of proportion to the injury (disproportionate to what would be expected for the fracture or soft tissue injury); constant, burning, unrelenting; NOT relieved by immobilisation or analgesics; (2) Pressure — the compartment feels tense and woody on palpation (turgid compartment); (3) Paraesthesia — pins and needles, altered sensation in the distribution of nerves running through the affected compartment; (4) Paralysis — weakness or loss of active movement of muscles within the affected compartment; a LATE sign — if paralysis is present, irreversible injury has likely occurred; (5) Passive stretch pain — the most specific clinical sign; pain on passive stretching of the muscles in the affected compartment (passive dorsiflexion for the anterior compartment of the leg — stretches the tibialis anterior; passive wrist/finger extension for the volar forearm compartment — stretches the flexor muscles); (6) Pulselessness — a very LATE and unreliable sign; pulses are maintained until arterial pressure itself is compromised; waiting for pulselessness = waiting too long
• The most important clinical signs: pain out of proportion to injury AND pain on passive stretch of the compartment muscles are the two most specific and actionable signs; the presence of either in an at-risk patient should prompt immediate compartment pressure measurement or fasciotomy
• Conscious vs unconscious patient: in the conscious patient, pain is the cardinal symptom — diagnosis is primarily clinical; in the unconscious, sedated, or obtunded patient (including post-operative patients, polytrauma, intoxicated patients, or patients with regional anaesthesia), pain cannot be assessed; the threshold for compartment pressure measurement must be very low in these patients; some centres advocate prophylactic fasciotomy in high-risk situations (tibial fracture + vascular repair; crush injury; prolonged limb compression) without waiting for clinical symptoms

• Technique: a needle (18 gauge) connected to a pressure monitoring system (commercial Stryker pressure monitor; or a simple saline column connected to an arterial pressure transducer) is inserted into the compartment at the level of the fracture or maximal swelling; the needle should be advanced into the muscle (not subcutaneously); measure each accessible compartment; the commercial Stryker device is the most common in UK emergency practice; document the diastolic blood pressure at the time of measurement to calculate delta P
• Pressure thresholds: absolute compartment pressure >30 mmHg = threshold for fasciotomy in most guidelines; delta P (diastolic BP − compartment pressure) <30 mmHg = threshold for fasciotomy; measure at multiple sites within each compartment (pressure may be highest at the fracture level); serial measurements every 1–2 hours if pressure is borderline (25–30 mmHg) and clinical picture is reassuring; do NOT rely on a single measurement
• Pitfalls: false-negative pressure measurement can occur if the needle is not in the correct compartment or is subcutaneous; measure at multiple sites; the clinical picture always takes precedence over a single pressure measurement; `treat the patient, not the number`

• Four compartments of the leg: (1) Anterior compartment — tibialis anterior, extensor hallucis longus (EHL), extensor digitorum longus (EDL), peroneus tertius; deep peroneal nerve and anterior tibial vessels; most commonly affected; foot drop from anterior compartment syndrome; (2) Lateral compartment — peroneus longus and brevis; superficial peroneal nerve; eversion of the foot; (3) Deep posterior compartment — flexor hallucis longus (FHL), flexor digitorum longus (FDL), tibialis posterior; posterior tibial nerve and tibial vessels; the most dangerous — difficult to access, late decompression leads to Volkmann`s of the foot; (4) Superficial posterior compartment — gastrocnemius and soleus; sural nerve; plantarflexion; less commonly the primary compartment affected but may be elevated
• Two-incision four-compartment fasciotomy of the leg (standard technique): (1) Lateral incision — a 15–20 cm longitudinal incision over the fibula, positioned between the anterior and lateral compartments; the anterior compartment fascia is incised anteriorly (anterior to the fibular shaft); the lateral compartment fascia is incised posteriorly (posterior to the fibular shaft); (2) Medial incision — a 15–20 cm longitudinal incision 2 cm posterior to the posteromedial border of the tibia; the superficial posterior compartment fascia is incised superficially; the deep posterior compartment is accessed by retracting the gastrocnemius and soleus posteriorly and incising the deep posterior fascial layer; the posterior tibial vessels and nerve must be protected
• Alternative — single-incision parafibular technique: a single long lateral incision allows access to all four compartments by extending both anteriorly and posteriorly; technically more demanding than the two-incision approach but avoids the medial incision; less commonly used in routine practice
• Wound management after fasciotomy: the fasciotomy wounds are left OPEN (not closed primarily); covered with non-adherent dressings and NPWT (negative pressure wound therapy/VAC); the swollen muscles will not allow closure at the time of decompression; formal wound closure or split skin grafting is performed at 48–72 hours when the swelling has reduced; never close a fasciotomy wound under tension — this defeats the purpose of decompression

• Forearm fasciotomy — Volkmann`s ischaemic contracture prevention: the forearm has three compartments — volar (flexors: FDS, FDP, FPL; median and ulnar nerves), dorsal (extensors: ECRB, ECRL, ECU, EDC, EIP, EPL, EPB, APL; posterior interosseous nerve), and the mobile wad (brachioradialis, ECRL, ECRB — partially included in the dorsal compartment); a volar curvilinear incision extending from the antecubital fossa to the carpal tunnel (Henry`s approach) decompresses the volar compartment and releases the carpal tunnel; a dorsal incision decompresses the dorsal compartment; the carpal tunnel MUST be released in forearm compartment syndrome (the increased pressure propagates into the hand)
• Compartments of the hand: 10 compartments (4 dorsal interossei, 3 volar interossei, adductor pollicis, thenar, hypothenar); decompressed via 2 dorsal longitudinal incisions (one between 2nd and 3rd metacarpals; one between 4th and 5th metacarpals) + a medial incision for the hypothenar compartment + a thenar incision

• 6 Ps: Pain (out of proportion — earliest, most sensitive), Pressure (turgid compartment), Paraesthesia (nerve ischaemia), Passive stretch pain (MOST SPECIFIC — pain on passive stretch of compartment muscles), Paralysis (late — irreversible damage likely), Pulselessness (very late — unreliable); diagnose before pulselessness
• Pressure thresholds: absolute >30 mmHg = fasciotomy; delta P (diastolic BP − compartment pressure) <30 mmHg = fasciotomy; ALWAYS calculate delta P to account for the patient`s haemodynamic status; hypotensive patients get compartment syndrome at lower absolute pressures
• Most common cause: tibial shaft fracture; most dangerous compartment: deep posterior (difficult access; tibialis posterior ischaemia → cavus foot; FHL/FDL → toe clawing; posterior tibial nerve → foot anaesthesia); Volkmann`s of the foot from missed deep posterior compartment syndrome
• Two-incision four-compartment leg fasciotomy: lateral incision (anterior + lateral compartments, one cut anterior and one posterior to fibula); medial incision (2 cm posterior to tibia — superficial and deep posterior compartments); all four compartments must be decompressed
• Fasciotomy wounds: leave OPEN; NPWT; formal closure or SSG at 48–72 hours when swelling resolves; NEVER close under tension; closing = re-creating compartment syndrome
• Unconscious/obtunded patients: cannot report pain — the cardinal symptom is absent; maintain very low threshold for pressure measurement; prophylactic fasciotomy for high-risk injuries (tibial fracture + vascular repair, prolonged compression, crush injury)
• Volkmann`s ischaemic contracture: classic result of missed forearm compartment syndrome; FDP and FPL ischaemic contracture = wrist flexed, fingers clawed, forearm pronated; intrinsic-minus hand; prevented by early fasciotomy; treated by muscle slide (Seddon/Page) or tendon lengthening in established contracture
• Time window: irreversible muscle necrosis begins at 6 hours of complete ischaemia; neurological damage earlier (nerve more sensitive to ischaemia than muscle); fasciotomy within 6 hours = best outcomes; >12 hours = high risk of permanent deficit; >24–36 hours = fasciotomy may actually worsen outcomes (reperfusion injury + rhabdomyolysis) — but this remains controversial and the risk-benefit must be assessed