Compartment Syndrome

Compartment syndrome is a rise in pressure inside a closed fascial compartment — a muscle group wrapped in a tough, largely inelastic fibrous sheath — high enough to compress the blood vessels running through it and cut off perfusion to the muscle and nerve tissue inside. The fascia's inelasticity is exactly what makes this dangerous: unlike skin, which can stretch to accommodate swelling, fascia does not yield, so swelling from a fracture, crush injury, or even a too-tight cast has nowhere to go and the pressure simply climbs inside the sealed space instead.

The classic teaching is the "six P's": pain (out of proportion to the apparent injury, and notably worsened by passively stretching the muscles in that compartment), pallor, paresthesia, pulselessness, paralysis, and poikilothermia. Pulselessness and paralysis are late signs, not early warning — waiting for the pulse to disappear means waiting until damage is already extensive, so the diagnosis is meant to be made on pain and stretch-sensitivity alone, well before the later signs appear.

Compartment syndrome is a true surgical emergency because muscle and nerve tissue begin dying within hours of losing blood supply, and the damage is largely irreversible once it happens — there is no effective medical treatment, only a fasciotomy: surgically cutting open the fascia to release the trapped pressure immediately, leaving the wound open temporarily rather than closing over tissue still under pressure. Delay measured in hours, not days, is the difference between a full recovery and permanent muscle and nerve loss or amputation.

Risk factors track anything that causes swelling in a sealed space fast: long bone fractures, crush injuries, and a cast or dressing applied without accounting for further swelling to come.