Compartment syndrome is the compression of nerves and blood vessels within an enclosed space. This leads to muscle and nerve damage and problems with blood flow.

Thick layers of tissue called fascia separate groups of muscles in the arms and legs from each other. Inside each layer of fascia is a confined space, called a compartment, that includes the muscle tissue, nerves, and blood vessels. Fascia surrounds these structures much like insulation covers wires.

Fascia do not expand, so any swelling in a compartment will lead to increasing pressure in that area, which will push on the muscles, blood vessels, and nerves. If this pressure is high enough, blood flow to the compartment will be blocked, which can lead to permanent injury to the muscle and nerves. If the pressure lasts long enough, the limb may die and need to be amputated.

Swelling leading to compartment syndrome is associated with trauma such as from a car accident or crush injury, or surgery. Compartment syndrome may also occur if you wear a tight bandage or a cast that is too tight.

Long-term (chronic) compartment syndrome can be caused by repetitive activities, such as running, which increase the pressure in a compartment only during that activity.

Compartment syndrome is most common in the lower leg and forearm, although it can also occur in the hand, foot, thigh and upper arm.

The hallmark symptom of compartment syndrome is severe pain that does not go away when you take pain medicine or raise the affected area. In more advanced cases, symptoms may include:

• Decreased sensation
• Paleness of skin
• Weakness

A physical exam will reveal:

• Severe pain when moving the affected area (for example, a person with compartment syndrome in the foot or lower leg will experience severe pain when moving the toes up and down)
• Tensely swollen and shiny skin
• Pain when the compartment is squeezed

Confirming the diagnosis involves directly measuring the pressure in the compartment. This is done using a needle attached to a pressure meter into the compartment. The needle is inserted into the affected area. Compartment syndrome is diagnosed if the pressure is greater than 45 mmHg or when the pressure is within 30 mmHg of the diastolic blood pressure (the lower number of the blood pressure).

When chronic compartment syndrome is suspected, this test must be performed immediately after the activity that causes pain.

Surgery is usually required. Long surgical cuts are made in the fascia to relieve the pressure. The wounds are generally left open (covered with a sterile dressing) and closed during a second surgery, usually 48-72 hours later. Skin grafts may be required to close the wound.

If a cast or bandage is causing the problem, the dressing should be loosened or cut down to relieve the pressure.

With prompt diagnosis and treatment, the outlook is excellent for recovery of the muscles and nerves inside the compartment. However, the overall prognosis will be determined by the injury leading to the syndrome.

Permanent nerve injury and loss of muscle function can result if the diagnosis is delayed. This is more common when injured person is unconscious or heavily sedated and cannot complain of the pain. Permanent nerve injury can occur after 12-24 hours of compression.

Complications include permanent injury to nerves and muscles that can dramatically impair function. (See: Volkmann's ischemia)

In more severe cases, amputation may be required.

Call your health care provider if you have had an injury and have severe swelling or pain that does not improve with pain medications.

There is probably no way to prevent this condition, however, early diagnosis and treatment will help prevent many of the complications.

Persons with casts need to be made aware of the risk of swelling and should see their health care provider or go to the emergency room if pain under the cast increases despite pain medicines and raising the area.

Geiderman JM. General Principles of Orthopedic Injuries. In: Marx J, ed. Rosen???s Emergency Medicine: Concepts and Clinical Practice. 6th ed. St Philadelphia, Pa: Mosby Elsevier; 2006:chap 46.