In a few brief hours, an arm or leg can be damaged to the point at which amputation is necessary. Although rare, compartment syndromes can occur without warning, after a musculoskeletal injury or surgery. Once swelling begins, your physician has only hours to intervene to prevent permanent damage. Compartment syndromes literally represent swelling out of control; however, this swelling is not visible to the eye because it occurs deep inside the limb. The painful condition results when swelling occurs within a group of muscles, nerves, and blood vessels within the arms, legs, feet, or buttocks enclosed within a membrane called fascia (Fig. 1). The fascia is tough and does not easily expand; therefore, when swelling occurs it causes pressure to build within the fascial compartment and the contents of the compartment can be damaged quickly.

Microcirculation
Although present throughout the body, the compartments most vulnerable to compartment syndrome are found in the forearm and lower leg. The circulatory blood pressure in our arteries averages 120 mm Hg, but in the capillaries the pressure drops to about 30 mm Hg. If surrounding pressures rise above that in the capillaries, nutrients cannot flow out to the cells and the byproducts of metabolism cannot be removed. In just hours, unnourished cells are exposed to damage. First they swell, and then they die releasing chemicals that cause further swelling. The additional swelling increases pressure, and a dangerous spiral can quickly develop into a serious medical emergency.

Ironically, pulses can still be felt on the other side of an involved compartment because arterial blood pressures are much higher, giving a false reassurance that all is well within the limb. It is, however, the circulation of the capillaries and cells that is being challenged and cut off causing the tissues it feeds to begin to die (Fig. 2). Tissues die at different rates; for example, nerve tissue cannot last more than a few hours without circulation. Beyond that, permanent paralysis results. Muscle tissue is not far behind. Besides the loss of the muscle's function, the dead muscle can release toxins that can cause kidney failure and death.

Diagnosis and treatment
Classic compartment syndromes can be caused by crushing or severe high-energy injuries to limbs in which the skin remains intact, however, they can appear with less serious injury or even after surgical procedures. Physicians suspect a compartment syndrome when the pain of an injury or surgery is out of proportion to what is anticipated. Tenseness and pain can be felt in the involved compartment when the muscles are stretched. If these positive clinical signs of the syndrome are present, the physician will measure the pressures within the compartment.

Treatment often involves an emergency surgery called a fasciotomy. During this procedure, the unyielding sleeve of fascia is literally split open to allow swelling to occur and to lower the rising pressures (Fig. 3). After surgery, the swelling subsides, the danger ends, and the fascia eventually reforms.

A curious variant of compartment syndrome, the exertional compartment syndrome, is known to affect some athletes. It occurs as a result of swelling to a compartment only during exercise, and it resolves rapidly when the activity ends. The condition rarely progresses to the dangerous spiral described above, but it can be disabling to an athlete by limiting his or her ability to participate. Exertional compartment syndrome can be diagnosed by a direct measurement of compartment pressures during exercise. If pressures in a given compartment rise to dangerous levels during the exercise period, a fasciotomy may be recommended and can be expected to end the condition permanently.

Fortunately, the out of control swelling that is associated with compartment syndromes is rare. Physicians are vigilant to detect them and the treatment is effective.

Fred Flandry, MD, FACS
Columbus, Georgia