Compartment Syndrome
Compartment syndrome is a surgical emergency caused by raised pressure within a closed fascial compartment, compromising tissue perfusion. The anterior compartment of the leg is most commonly affected.
Key Facts
- Pain out of proportion to the clinical situation is the earliest and most reliable symptom
- Pain on passive stretch of muscles in the affected compartment is the most sensitive clinical sign
- Clinical diagnosis - do NOT wait for pressure measurements if clinical suspicion is high; treat urgently
- Normal compartment pressure: <10 mmHg; >30 mmHg or within 30 mmHg of diastolic BP = compartment syndrome
- Emergency fasciotomy is the definitive treatment - must be performed within 6 hours to prevent irreversible muscle necrosis
- Most common cause: Fractures (especially tibial shaft); also crush injuries, burns, vascular injury, tight casts/dressings
- Anterior compartment of the leg is the most commonly affected; deep peroneal nerve and anterior tibial artery are at risk
- Late signs (pulselessness, paralysis, pallor) indicate irreversible damage - fasciotomy may not save the limb at this stage
Overview
Key Facts
Compartment syndrome is a time-critical emergency. Clinical suspicion must lead to urgent action - delays result in irreversible muscle necrosis, contracture, and potential amputation.
Epidemiology
Incidence ~3.1 per 100,000/year. Most common in young males (higher muscle mass). Tibial fractures account for ~40% of cases. Also occurs in forearm (supracondylar fractures in children), thigh, hand, foot, buttock.
Aetiology
Increased compartment contents:
- Fractures (especially tibial shaft)
- Crush injuries
- Post-ischaemic swelling (after revascularisation)
- Burns
- Haemorrhage (anticoagulants)
- Snake bite
Decreased compartment size:
- Tight casts/dressings/bandages
- Circumferential burns with eschar
- Closure of fascial defects
Pathophysiology
- Raised pressure within closed fascial compartment → exceeds capillary perfusion pressure (~25-30 mmHg)
- Muscle and nerve ischaemia → cellular oedema → further pressure increase → vicious cycle
- Irreversible muscle necrosis begins after ~6 hours of ischaemia
- Volkmann's ischaemic contracture: End result of untreated forearm compartment syndrome - fibrosis and contracture of flexor muscles
Clinical Presentation
Five Ps (but early signs are most important)
- Pain: Out of proportion, not relieved by analgesia, worsened by passive stretch of affected muscles (EARLIEST and MOST IMPORTANT)
- Pressure: Tense, swollen compartment
- Paraesthesia: Numbness in distribution of nerve traversing compartment
- Paralysis: LATE sign - indicates irreversible damage
- Pulselessness: Very LATE sign - pulses are usually present as compartment pressure rarely exceeds arterial pressure
By Location
- Leg (anterior compartment): Pain on passive plantarflexion; numbness in 1st web space (deep peroneal nerve); weakness of dorsiflexion
- Forearm (volar compartment): Pain on passive extension of fingers; weakness of finger flexion
- Thigh: Less common; massive swelling post-fracture
Red Flags
- Increasing analgesic requirement despite adequate fracture immobilisation
- Pain on passive stretch of the involved muscles
- Paraesthesia - nerve ischaemia has begun
- Tense, swollen limb segment
- Remember: Compartment syndrome can occur WITH intact distal pulses
Differential Diagnosis
| Diagnosis | Key Distinguishing Features | Investigation |
|---|---|---|
| Fracture pain | Pain proportionate, improving with immobilisation | X-ray |
| DVT | Calf swelling, warmth, but not tense compartment | D-dimer, US Doppler |
| Arterial injury | Absent pulses, pale/cold limb, no compartment tension | CT angiography |
| Cellulitis | Erythema, warmth, fever; no pain on passive stretch | Clinical, bloods |
| Rhabdomyolysis | Muscle pain, dark urine, raised CK; may coexist with compartment syndrome | CK, myoglobin |
Diagnosis / Investigation
Clinical (Most Important)
- Clinical diagnosis is paramount - do NOT delay for measurements if suspicion is high
- Pain on passive stretch: Most sensitive clinical sign
Compartment Pressure Measurement
- Stryker needle/manometer: Measure directly
- Absolute pressure >30 mmHg: Diagnostic
- Delta pressure (diastolic BP − compartment pressure) <30 mmHg: Indicates compartment syndrome
- Only measure if diagnosis uncertain and patient cannot reliably report symptoms (e.g., obtunded, sedated)
Bloods
- CK: Elevated from muscle necrosis (rhabdomyolysis)
- U&Es: Myoglobin → AKI; hyperkalaemia from cell death
- Myoglobin: In urine
- FBC, coagulation: Baseline
Management
Emergency Treatment
- Remove all constricting material: Split casts/dressings/bandages to skin immediately
- Keep limb at heart level: NOT elevated (elevation reduces perfusion pressure)
- Emergency fasciotomy: Within 6 hours of symptom onset - definitive treatment
Fasciotomy
Leg (4 compartments):
- Two-incision technique: Lateral incision (anterior and lateral compartments) + medial incision (superficial and deep posterior compartments)
- All 4 compartments MUST be released
- Leave wounds open → delayed primary closure or skin grafting at 48-72 hours
Forearm:
- Volar incision from proximal to distal; carpal tunnel also released
Post-Fasciotomy
- Wound left open: Temporary coverage with VAC/dressings
- Second look at 48-72 hours: Assess muscle viability; debride necrotic tissue
- Delayed closure: Primary closure, split-skin graft, or secondary intention
- Aggressive IV fluids: Prevent rhabdomyolysis-related AKI (target UO >1 mL/kg/hr)
Referral Criteria
- ALL suspected compartment syndrome - immediate orthopaedic/surgical review
- Do NOT delay for investigations
Prognosis
- Fasciotomy within 6 hours: Good functional outcome in most cases
- Fasciotomy after 6 hours: Increasing risk of irreversible muscle necrosis, nerve damage
- Delayed/missed diagnosis: Volkmann's contracture (forearm), muscle necrosis, amputation, rhabdomyolysis, AKI, hyperkalaemia, cardiac arrest
- Mortality: From complications (rhabdomyolysis, AKI, sepsis) - overall low if treated promptly
- Medicolegal significance: Missed compartment syndrome is a common source of litigation in orthopaedics
Other Relevant Information
Compartments of the Leg
| Compartment | Key Muscles | Key Nerve | Key Artery |
|---|---|---|---|
| Anterior | Tibialis anterior, EDL, EHL | Deep peroneal | Anterior tibial |
| Lateral | Peroneus longus, brevis | Superficial peroneal | - |
| Superficial posterior | Gastrocnemius, soleus | Sural (sensory) | - |
| Deep posterior | Tibialis posterior, FDL, FHL | Tibial | Posterior tibial, peroneal |