Pathophysiology
Clinical meaning
Compartment syndrome occurs when pressure within a closed fascial compartment exceeds capillary perfusion pressure, causing tissue ischemia and necrosis. Normal compartment pressure is 0-8 mmHg; clinical concern begins at >30 mmHg or within 30 mmHg of diastolic blood pressure (delta pressure). Increased pressure results from internal expansion (hemorrhage, edema from fractures, crush injuries, reperfusion injury) or external compression (casts, tight bandages, circumferential burns). Ischemia triggers an inflammatory cascade increasing capillary permeability and further edema, creating a vicious cycle. Irreversible muscle necrosis begins at 4-6 hours of ischemia; nerves are damaged at 4 hours. The anterior compartment of the leg is most commonly affected. Untreated, it leads to Volkmann contracture (forearm) or permanent functional loss.