Compartment Syndrome

Compartment syndrome occurs when pressure within a closed osteofascial compartment rises sufficiently to impair local tissue perfusion. Progressive venous obstruction increases interstitial oedema, reduces the arteriovenous pressure gradient and ultimately compromises capillary blood flow, producing muscle and nerve ischaemia.

The clinically important distinction is between acute compartment syndrome, which is a limb threatening surgical emergency, and chronic exertional compartment syndrome, which is exercise induced and usually treated electively.

Acute compartment syndrome most commonly affects the leg and forearm but can occur in the thigh, foot, hand, buttock and upper arm.

Major causes include:

• Tibial shaft fracture
• High energy tibial plateau fracture
• Forearm fractures
• Crush injury
• Reperfusion after arterial occlusion
• Tight casts or circumferential dressings
• Intramuscular haemorrhage, particularly with anticoagulation or coagulopathy
• Vascular injury
• Burns
• Prolonged limb compression in an unconscious patient
• Extravasation of pressurised IV fluid
• Vigorous exercise in susceptible patients

A fracture does not need to be present. Conversely, an open fracture does not protect against compartment syndrome.

Anatomical compartments of the leg

There are four major compartments:

Anterior

Contains:

• Tibialis anterior
• Extensor hallucis longus
• Extensor digitorum longus
• Deep peroneal nerve
• Anterior tibial vessels

Lateral

Contains:

• Peroneus longus
• Peroneus brevis
• Superficial peroneal nerve

Superficial posterior

Contains:

• Gastrocnemius
• Soleus
• Plantaris

Deep posterior

Contains:

• Tibialis posterior
• Flexor hallucis longus
• Flexor digitorum longus
• Tibial nerve
• Posterior tibial vessels

The deep posterior compartment is particularly easy to inadequately decompress.

Forearm compartments

The forearm contains:

• Volar compartment
• Dorsal compartment
• Mobile wad containing brachioradialis and radial wrist extensors

The carpal tunnel may require simultaneous decompression when median nerve pressure is clinically significant.

Acute versus chronic exertional syndrome

Acute compartment syndrome

Rapid rise in pressure with threatened muscle and nerve viability. Requires emergency fasciotomy when established.

Chronic exertional compartment syndrome

Reversible exercise induced rise in compartment pressure. Symptoms resolve with rest and there is no ongoing tissue necrosis between episodes.

Diagnosis is primarily clinical and requires repeated examination.

The earliest and most useful findings are:

• Pain disproportionate to the apparent injury
• Increasing analgesic requirement
• Pain with passive stretch of muscles within the affected compartment
• Tense or firm compartment
• Progressive sensory disturbance

Pain may become less prominent late when nerves and muscle have infarcted. Therefore, sudden improvement in pain in a severely compromised limb is not necessarily reassuring.

The classical five Ps are:

• Pain
• Paraesthesia
• Pallor
• Paralysis
• Pulselessness

Only pain and paraesthesia are useful early. Paralysis and pulselessness are late findings.

A normal arterial pulse does not exclude compartment syndrome.

Compartment pressure sufficient to destroy microvascular muscle perfusion can exist while major arteries remain patent.

In children, useful warning features include:

• Anxiety
• Agitation
• Increasing analgesic requirement

Patients at particularly high risk of missed compartment syndrome include:

• Unconscious trauma patients
• Intubated patients
• Patients receiving regional anaesthesia or heavy sedation
• Children unable to describe symptoms
• Patients with neurological injury

Serial examination should be documented.

Do not delay fasciotomy for imaging when clinical compartment syndrome is clear.

Compartment pressure measurement is useful when:

• Examination is unreliable
• Findings are equivocal
• The patient is unconscious
• Multiple injuries obscure the pain response

A commonly used parameter is:

Delta pressure = diastolic blood pressure minus measured compartment pressure

A delta pressure of 30 mmHg or less strongly supports clinically important compartment hypoperfusion. No single absolute pressure value should replace clinical judgement, and pressure trends can be more useful than a single measurement.

A compartment pressure around or above 30 mmHg is concerning, particularly in a hypotensive patient.

Pressure should be measured in each clinically relevant compartment and close to the level of injury.

Laboratory abnormalities such as elevated creatine kinase, myoglobinuria and metabolic acidosis indicate muscle injury but are too late and nonspecific to establish or exclude the diagnosis.

Immediate measures

While preparing for definitive treatment:

• Remove circumferential casts and tight dressings completely
• Release constrictive splints
• Correct systemic hypotension
• Maintain the limb approximately at heart level

Do not elevate the limb substantially above the heart when acute compartment syndrome is suspected because this can further reduce arterial perfusion pressure.

Do not rely on analgesia and observation when symptoms continue to progress.

Fasciotomy

Established acute compartment syndrome requires emergency complete fasciotomy.

Delay progressively increases irreversible muscle and nerve injury.

Muscle can sustain reversible ischaemia for only a limited period. After prolonged complete ischaemia, muscle necrosis, neurological deficit, contracture, rhabdomyolysis and renal injury become increasingly likely.

Leg fasciotomy

The standard technique is a two incision four compartment fasciotomy.

Lateral incision

Decompress:

• Anterior compartment
• Lateral compartment

Identify and protect the superficial peroneal nerve.

Medial incision

Decompress:

• Superficial posterior compartment
• Deep posterior compartment

The soleus must be released adequately from its tibial origin to expose and decompress the deep posterior compartment.

Incomplete release of the deep posterior compartment is a recognised technical failure.

Forearm fasciotomy

A generous volar fasciotomy should decompress the flexor compartments.

Extend decompression proximally or distally according to the injury.

Add:

• Carpal tunnel release when indicated
• Dorsal fasciotomy when the dorsal compartment remains tense after volar decompression

The skin must remain open if primary closure creates tension.

Muscle assessment

At surgery, evaluate muscle viability using:

• Colour
• Contractility
• Consistency
• Capacity to bleed

Clearly necrotic muscle should be excised.

Muscle of uncertain viability is better reassessed at planned second look surgery rather than aggressively sacrificed during the first operation when viability is genuinely uncertain.

Second look and wound closure

Return to theatre commonly at approximately 24 to 48 hours for:

• Repeat muscle assessment
• Further debridement
• Wound irrigation
• Planning of closure

Do not close swollen fasciotomy wounds under tension.

Options include:

• Delayed primary closure
• Gradual dermatotraction
• Split thickness skin graft

Rhabdomyolysis

Extensive muscle necrosis can produce:

• Hyperkalaemia
• Hypocalcaemia early
• Metabolic acidosis
• Myoglobinuria
• Acute kidney injury

Monitor:

• Potassium
• Creatinine
• Calcium
• Phosphate
• Creatine kinase
• Urine output

Use aggressive isotonic IV fluid resuscitation when rhabdomyolysis is present while avoiding uncontrolled volume overload.

Treat dangerous hyperkalaemia immediately.

Late presentation

When presentation is extremely delayed and muscle and nerve are clearly irreversibly necrotic, routine fasciotomy can expose large amounts of dead tissue and substantially increase infection and systemic complications. Management must be individualised according to tissue viability, systemic toxicity and reconstructive potential rather than automatically opening every late compartment.

Chronic exertional compartment syndrome

Typical symptoms are predictable pain, tightness, paraesthesia or weakness beginning after a reproducible duration of exercise and resolving after activity stops.

The anterior and lateral leg compartments are commonly involved.

Pressure criteria traditionally used include one or more of:

• Resting pressure 15 mmHg or greater
• Pressure 30 mmHg or greater at 1 minute after exercise
• Pressure 20 mmHg or greater at 5 minutes after exercise

These thresholds should be interpreted alongside the clinical history rather than used in isolation.

Initial treatment includes:

• Activity modification
• Alteration of training load
• Running gait assessment where relevant
• Correction of biomechanics

Persistent function limiting disease despite conservative treatment can undergo elective compartment fasciotomy.

Unlike acute compartment syndrome, this is not an emergency.