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 |