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Musculoskeletal · Clinical Topics
Compartment Syndrome
Compartment syndrome is a surgical emergency where increased pressure within a closed osteofascial compartment compromises blood flow and tissue perfusion. It most commonly occurs following a fracture (especially the tibia) or crush injury. Prompt diagnosis is clinical, and management requires emergency fasciotomy to prevent muscle necrosis and limb loss.
📌 Learning Objectives
- Define compartment syndrome and its pathophysiology.
- Identify the common causes and risk factors for compartment syndrome.
- Recognise the early clinical signs and symptoms of compartment syndrome.
- Explain the diagnostic approach, including the role of intra-compartmental pressure measurement.
- Outline the emergency management steps for compartment syndrome, including fasciotomy.
- Describe the potential complications of delayed diagnosis and treatment.
📋 Overview
Compartment syndrome is a critical condition where elevated pressure within a confined osteofascial compartment compromises capillary perfusion, leading to muscle and nerve ischaemia. It's a true surgical emergency. The lower leg, particularly the anterior compartment after a tibial shaft fracture, is the most common site. Other causes include crush injuries, burns, reperfusion injury, and tight casts. The key clinical feature is pain 'out of proportion' to the injury, unrelieved by analgesia, and exacerbated by passive stretching of the affected muscles. Late signs like pulselessness and paralysis indicate irreversible damage. Diagnosis is primarily clinical, but intra-compartmental pressure (ICP) measurement can aid in equivocal cases. A 'Delta pressure' (Diastolic BP - ICP) of <30 mmHg is highly suggestive. Immediate management involves removing all constrictive dressings and emergency fasciotomy; the limb should NOT be elevated.
🔬 Basic Science
Muscles are organised into compartments by rigid, non-compliant fascia. According to the modified Munro-Kellie doctrine for limbs, any increase in volume (e.g., oedema, haemorrhage) within this fixed space causes a rise in intra-compartmental pressure (ICP). Initially, this impedes low-pressure venous outflow, exacerbating oedema. As ICP continues to rise, it eventually exceeds capillary perfusion pressure, leading to ischaemia. Nerve tissue is highly sensitive to ischaemia, with damage potentially occurring within 2 hours. Muscle necrosis typically begins after 4-6 hours. This tissue death releases myoglobin, which can precipitate in renal tubules, causing acute tubular necrosis and subsequent acute kidney injury.
🏥 Clinical Relevance
Recognising compartment syndrome is critical. The '6 Ps' are a mnemonic, but focus on the early signs: 'Pain out of proportion' (often the first and most reliable), Paresthesia (early nerve ischaemia), and a 'tense' compartment on palpation. Passive stretch of the muscles within the compartment (e.g., passive dorsiflexion/plantarflexion of the ankle for lower leg compartments) will elicit severe pain. Common pitfalls include dismissing pain as 'normal for the injury' or waiting for absent pulses. A palpable distal pulse does NOT rule out compartment syndrome. Delayed treatment leads to irreversible muscle necrosis, nerve damage, and severe functional impairment, such as Volkmann's ischaemic contracture (a claw-like deformity, typically of the hand/forearm). Systemic complications from rhabdomyolysis (muscle breakdown) include hyperkalaemia, metabolic acidosis, and acute kidney injury.
🧪 Investigations
- Clinical Assessment: The most crucial 'investigation'. Assess pain, neurological function (sensation, motor), and palpate compartment tension. Check distal pulses (often present early).
- Intra-compartmental Pressure (ICP) Measurement: Using a Stryker device or similar. Indicated if clinical diagnosis is equivocal, in uncooperative patients, or those with altered consciousness. A Delta pressure (Diastolic BP - ICP) <30 mmHg is a strong indication for fasciotomy. Absolute ICP >30-40 mmHg is also concerning.
- Bloods: FBC, U&E (monitor for hyperkalaemia, rising creatinine), Creatine Kinase (CK - will be significantly elevated due to muscle breakdown), Myoglobin (serum and urine - indicates rhabdomyolysis and risk of renal damage).
- Intra-compartmental Pressure (ICP) Measurement: Using a Stryker device or similar. Indicated if clinical diagnosis is equivocal, in uncooperative patients, or those with altered consciousness. A Delta pressure (Diastolic BP - ICP) <30 mmHg is a strong indication for fasciotomy. Absolute ICP >30-40 mmHg is also concerning.
- Bloods: FBC, U&E (monitor for hyperkalaemia, rising creatinine), Creatine Kinase (CK - will be significantly elevated due to muscle breakdown), Myoglobin (serum and urine - indicates rhabdomyolysis and risk of renal damage).
💊 Management
This is an emergency. The priority is to reduce compartment pressure and restore perfusion.
1. **Immediate first aid:** Remove all constrictive dressings, bandages, and casts down to the skin. Loosen any tight clothing.
2. **Positioning:** Keep the limb at the level of the heart (neutral position). Do NOT elevate the limb, as this reduces arterial inflow and exacerbates ischaemia.
3. **Supportive care:** High-flow oxygen, IV fluid resuscitation (to prevent renal injury from myoglobinuria), and analgesia.
4. **Surgical:** Emergency Fasciotomy. This is the definitive treatment. For the lower leg, this typically involves two long incisions (anterolateral and posteromedial) to decompress all four compartments (anterior, lateral, superficial posterior, deep posterior). The wounds are left open and typically reviewed in 48-72 hours for debridement and delayed closure or skin grafting.
1. **Immediate first aid:** Remove all constrictive dressings, bandages, and casts down to the skin. Loosen any tight clothing.
2. **Positioning:** Keep the limb at the level of the heart (neutral position). Do NOT elevate the limb, as this reduces arterial inflow and exacerbates ischaemia.
3. **Supportive care:** High-flow oxygen, IV fluid resuscitation (to prevent renal injury from myoglobinuria), and analgesia.
4. **Surgical:** Emergency Fasciotomy. This is the definitive treatment. For the lower leg, this typically involves two long incisions (anterolateral and posteromedial) to decompress all four compartments (anterior, lateral, superficial posterior, deep posterior). The wounds are left open and typically reviewed in 48-72 hours for debridement and delayed closure or skin grafting.
Revision Resources – expand the sections below for high-yield notes, exam pearls, key facts and further reading.
MLA High-Yield Notes & Quick Revision ⌄
SBA Trap: A patient with a tibial fracture develops severe pain unrelieved by morphine, but has palpable distal pulses. What is the most appropriate next step? Answer: Emergency fasciotomy. The presence of pulses does NOT rule out compartment syndrome. This is a classic exam scenario.
OSCE Pearl: When examining a patient for compartment syndrome, always demonstrate passive stretch of the muscles in the affected compartment (e.g., passive dorsiflexion/plantarflexion of the ankle for lower leg). Palpate the compartment for tension. Be able to explain why elevation is contraindicated.
Viva Question: What are the systemic complications of compartment syndrome? (Rhabdomyolysis, hyperkalaemia, metabolic acidosis, acute kidney injury).
Common Misconception: That compartment syndrome only occurs with obvious trauma. It can occur with less obvious injuries, prolonged limb compression (e.g., drug overdose), or even after revascularisation procedures (reperfusion injury).
Paediatric Considerations: Diagnosis is harder in children due to communication difficulties. Look for 'the 3 As': Agitation, Anxiety, and Analgesic requirement out of proportion to injury.
OSCE Pearl: When examining a patient for compartment syndrome, always demonstrate passive stretch of the muscles in the affected compartment (e.g., passive dorsiflexion/plantarflexion of the ankle for lower leg). Palpate the compartment for tension. Be able to explain why elevation is contraindicated.
Viva Question: What are the systemic complications of compartment syndrome? (Rhabdomyolysis, hyperkalaemia, metabolic acidosis, acute kidney injury).
Common Misconception: That compartment syndrome only occurs with obvious trauma. It can occur with less obvious injuries, prolonged limb compression (e.g., drug overdose), or even after revascularisation procedures (reperfusion injury).
Paediatric Considerations: Diagnosis is harder in children due to communication difficulties. Look for 'the 3 As': Agitation, Anxiety, and Analgesic requirement out of proportion to injury.
Acute limb ischaemia
Trauma management
Post-operative complications
Electrolyte disturbances (Hyperkalaemia)
Acute kidney injury
- Surgical emergency due to increased pressure in a closed osteofascial compartment.
- Compromises blood flow, leading to muscle and nerve ischaemia.
- Most common after tibial fractures, crush injuries.
- Cardinal sign: Pain 'out of proportion', unrelieved by analgesia, worsened by passive stretch.
- Diagnosis is primarily clinical; ICP measurement aids equivocal cases.
- Delta pressure (Diastolic BP - ICP) <30 mmHg is highly suggestive.
Exam Pearls ⌄
⭐ High Yield
Compartment syndrome is a surgical emergency requiring immediate fasciotomy.
Pain 'out of proportion' to injury, unrelieved by analgesia, and worsened by passive stretch is the cardinal early sign.
The '6 Ps' are classic, but pallor, paresis, and pulselessness are LATE signs of irreversible damage.
Limb elevation is CONTRAINDICATED as it reduces perfusion pressure.
A Delta pressure (Diastolic BP - ICP) <30 mmHg strongly indicates the need for fasciotomy.
Most common after tibial fractures and crush injuries.
Systemic complications include rhabdomyolysis, hyperkalaemia, and acute kidney injury.
💡 Clinical Pearl
Acute Kidney Injury: Rhabdomyolysis from muscle necrosis in compartment syndrome can lead to myoglobinuria and acute tubular necrosis.
Hyperkalaemia: Muscle breakdown releases potassium, leading to hyperkalaemia, a life-threatening electrolyte imbalance.
Deep Vein Thrombosis: Prolonged immobility or limb compression can increase DVT risk, though not a direct cause of compartment syndrome, it's a co-morbidity to consider in trauma patients.
⚠️ Exam Tip — Common Mistakes
Dismissing 'pain out of proportion' as normal post-injury pain.
Waiting for absent distal pulses to diagnose compartment syndrome.
Elevating the affected limb, which worsens ischaemia.
Delaying surgical intervention (fasciotomy) once diagnosis is suspected.
Underestimating the systemic complications of rhabdomyolysis.
Key Facts ⌄
Surgical emergency: high risk of limb loss, permanent disability (e.g., Volkmann's ischaemic contracture), or systemic complications (e.g., renal failure).
Most common after tibial fractures, crush injuries, or reperfusion injury.
Cardinal sign: Pain out of proportion to injury, unrelieved by analgesia, and worsened by passive stretch of muscles in the affected compartment.
The '6 Ps' (Pain, Paresthesia, Pressure, Pallor, Paresis, Pulselessness) are classic signs, but Pallor, Paresis, and Pulselessness are LATE indicators of irreversible damage – do not wait for them.
Management: Immediate removal of all constrictive dressings and emergency fasciotomy.
Limb elevation is CONTRAINDICATED as it further reduces the perfusion pressure gradient.
Systemic complications include rhabdomyolysis, hyperkalaemia, metabolic acidosis, and acute kidney injury.
Related Topics ⌄
References ⌄
- BOAST (British Orthopaedic Association) Guidelines for the Management of Compartment Syndrome
- NICE CKS - Fractures
- Kumar & Clark's Clinical Medicine
Further Resources
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