Acute Compartment Syndrome
Orthopedic Surgery
Illness script · Orthopedic Surgery
Acute Compartment Syndrome
Elevated pressure within a closed fascial compartment compromises perfusion, causing ischemia and irreversible muscle/nerve damage if untreated.
This illness script for Acute Compartment Syndrome covers predisposing factors, classic presentation, mechanism, workup, management, and the clinical pivots that separate it from look-alikes—written for USMLE Step 1 and clerkship reasoning.
01
Predisposing factors
- Tibial shaft fracture is #1 cause (~40% of cases)
- Crush injuries, burns, reperfusion after vascular injury
- Tight casts/splints or circumferential dressings
- Coagulopathy or anticoagulation use increases risk
- High-pressure injection injuries; young muscular patients at higher risk (less compliant compartments)
02
Presentation
- Classic 6 P's: Pain (out of proportion), Pressure (tense compartment), Paresthesias, Paralysis, Pallor, Pulselessness
- Pain with passive stretch of muscles in affected compartment — earliest & most sensitive sign
- Tense, woody compartment on palpation
- Paresthesias (e.g., first web space in anterior leg) precede motor loss
- Pulses may be preserved until very late — do NOT reassure
- Most common site: anterior compartment of lower leg
03
Pathophysiology
- Rising interstitial pressure exceeds capillary perfusion pressure (~30 mmHg threshold)
- Venous outflow obstructed first → arterial inflow eventually compromised
- Ischemia → cell swelling → further pressure increase (vicious cycle)
- Irreversible muscle/nerve necrosis within 6–8 hours of ischemia
04
Diagnostics
- Clinical diagnosis in conscious patients — do not delay fasciotomy waiting for measurements
- Compartment pressure >30 mmHg OR within 30 mmHg of diastolic BP (ΔP <30 mmHg) = indication for fasciotomy
- Stryker device or needle manometer for measurement in obtunded/uncooperative patients
- Elevated CK/myoglobinuria indicates muscle necrosis already occurring
- X-ray to identify fracture but does not diagnose ACS
05
Management
- Emergent fasciotomy — definitive and only effective treatment; do NOT delay
- Remove all circumferential dressings/casts immediately
- Limb at heart level (not elevated — reduces perfusion pressure)
- IV fluids + urine alkalinization if myoglobinuria present (prevent renal failure)
- Fasciotomy wound left open, closed at 48–72 h or split-thickness skin graft
06
Clinical pivots
How to separate this script from the look-alikes that show up on exams and on the wards.
Peripheral arterial occlusion
ACS has tense compartment + pain with passive stretch; arterial occlusion shows collapsed compartment and absent Doppler signal early
Deep vein thrombosis
DVT causes pitting edema and no pain with passive stretch; compartment is soft, not woody
Nerve injury (neuropraxia)
Neuropraxia lacks tense compartment and elevated pressure measurement; no progressive motor loss trajectory
Necrotizing fasciitis
NF shows skin necrosis, crepitus, systemic sepsis, and pain out of proportion but with soft/fluctuant tissue rather than tense compartment
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Educational use only. This illness script is a study framework, not medical advice. Confirm decisions with current guidelines and your clinical supervisors.