Compartment Syndrome

Acute compartment syndrome is a surgical emergency. Your muscles are organized into tightly-packaged groups (compartments) wrapped in a tough sheath of tissue that doesn't stretch. When pressure inside one of those compartments climbs higher than the small blood vessels can push against, blood flow to the muscle and nerve cuts off. Without surgery to release that pressure within about 4 to 6 hours, the muscle dies — and the consequences are permanent (a Volkmann contracture in the forearm, foot drop in the leg).

Compartment syndrome can follow a fracture, a crush injury, a burn, or even a cast that ends up too tight. Doctors used to teach a list of six warning signs (the 6 P's: pain, pressure, paralysis, abnormal sensation, pallor, no pulse), but most of those show up too late to be useful. The two earliest, most reliable warnings: pain that is way out of proportion to the injury, and severe pain when someone passively stretches the muscles in the affected limb.

The hallmark is pain that is wildly out of proportion to the visible injury. A forearm or lower leg that should hurt moderately after a fracture instead produces severe, deep, unrelenting pain that does not respond to the usual doses of pain medication. The limb feels tense and swollen — hard to the touch rather than soft — and the skin may look shiny and stretched.

The single most reliable early warning sign is the passive stretch test: if someone gently extends your fingers or toes and the pain in the affected compartment spikes dramatically, that points strongly toward rising compartment pressure. Late signs — numbness, inability to move the fingers or toes, pale or dusky skin, and absent pulse — mean irreversible damage may already be underway. Do not wait for those to appear before seeking emergency care.

When the clinical picture raises suspicion, your surgeon measures the actual pressure inside the compartment using a needle device. The standard threshold for emergency surgery is a delta-P (the difference between your blood pressure and the compartment pressure) of 30 mmHg or less. Critically: do NOT wait for the pulse to disappear — that's a very late sign and means the artery itself is being squeezed off, well past the point of reversible damage.

Once the pressure threshold is met (or when the clinical signs are unmistakable but a patient can't communicate well enough for the bedside exam), an emergency fasciotomy is performed without delay — the surgeon makes long incisions through the tough sheath that wraps the muscle compartment, releasing the pressure and restoring blood flow.

External patient-education references and related OSI pages for additional background:

• Britannica — Human skeleton
• AAOS OrthoInfo — patient education library
• OSI glossary — orthopedic terminology in plain language