Compartment Syndrome

How compartment syndrome happens

Muscles in the limbs are grouped into compartments, each wrapped in tough, inelastic tissue called fascia. The lower leg has four compartments; the forearm has three. Because fascia does not stretch, swelling or bleeding inside a compartment raises the pressure.

When pressure exceeds the pressure in small veins and capillaries, blood cannot flow through the tissue. Muscles and nerves become starved of oxygen. Muscle starts to die after about 4 to 6 hours, and nerve damage can begin sooner. This sets up a vicious cycle: damaged tissue swells further.

Acute compartment syndrome

Causes

• Fractures: the most common cause, particularly fractures of the tibia (shin bone) and forearm; can occur with both closed and open fractures
• Crush injuries and severe soft tissue bruising
• Tight casts, splints or bandages
• Reperfusion: after blood flow is restored to a limb following a blocked artery or vascular surgery
• Prolonged limb compression: lying on a limb for hours after an overdose, intoxication or stroke
• Burns, especially circumferential burns
• Bleeding into a compartment, especially on blood thinners or with hemophilia
• Snake bites, IV fluid leakage, intense exercise (rarely)

Symptoms

The classic "5 Ps" are described, but most appear late:

• Pain: the earliest and most important sign. Severe, deep, out of proportion to the injury, unrelieved by usual pain medicine, and worse when the muscles in the compartment are passively stretched (for example, gently moving the toes).
• Paresthesia: tingling or numbness, an early nerve sign
• Pallor: pale skin (late)
• Paralysis: weakness (late)
• Pulselessness: usually a very late sign; a normal pulse does not rule out compartment syndrome

The compartment often feels tense and wooden.

In unconscious or sedated patients and young children, pain cannot be reported, so pressure monitoring is used.

Diagnosis

Diagnosis is primarily clinical. When uncertain, a needle device measures compartment pressure. A pressure within 30 mmHg of the diastolic blood pressure (a "delta pressure" below 30) indicates compartment syndrome needing surgery. Blood tests for creatine kinase and urine tests look for muscle breakdown (rhabdomyolysis).

Treatment

1. Remove or split any cast and dressings down to the skin.
2. Keep the limb at heart level (not raised high, which reduces blood flow).
3. Give oxygen and fluids; correct low blood pressure.
4. Emergency fasciotomy: a surgeon makes long cuts through the skin and fascia to release the pressure. Wounds are left open and closed days later, sometimes with skin grafts.

Fasciotomy should ideally be done within about 6 hours of onset to save muscle and nerve function.

Complications

• permanent muscle damage and contracture (Volkmann's contracture in the forearm)
• nerve damage with numbness, weakness or foot drop
• kidney failure from rhabdomyolysis
• infection of fasciotomy wounds
• amputation in severe or late cases

Chronic exertional compartment syndrome

Chronic exertional compartment syndrome (CECS) affects mainly runners, soldiers and athletes in sports with repetitive running.

• Pain, tightness, cramping or burning in the lower leg (most often the front or deep back compartments) starts at a predictable time or distance during exercise.
• Symptoms ease within about 10 to 30 minutes of stopping.
• It is often in both legs.
• Some people have numbness in the foot or temporary foot drop.

It is diagnosed by measuring compartment pressures before and after exercise, after excluding shin splints, stress fractures and artery entrapment.

Treatment includes changing running technique (for example, switching from heel strike to forefoot strike), reducing training, cross-training and physical therapy. Persistent cases are treated with surgical fasciotomy, which has good success rates. CECS does not usually cause permanent damage.

Frequently asked questions

What are the signs of compartment syndrome?

The main early sign is severe pain that is out of proportion to the injury and gets worse when the muscles are stretched, such as moving the fingers or toes. Other signs include a tight, swollen limb, tingling and numbness. Pale skin, weakness and loss of pulse are late signs.

What causes compartment syndrome?

Acute compartment syndrome is usually caused by fractures, especially of the shin or forearm, crush injuries, tight casts or bandages, burns, bleeding, or restored blood flow after a blocked artery. Chronic exertional compartment syndrome is caused by repetitive exercise, mainly running.

Is compartment syndrome an emergency?

Acute compartment syndrome is a surgical emergency. Pressure must be relieved, usually by fasciotomy, within hours to prevent permanent muscle and nerve damage. Chronic exertional compartment syndrome is not an emergency and settles with rest.

Can compartment syndrome go away on its own?

Acute compartment syndrome does not go away on its own and worsens without treatment. Chronic exertional compartment syndrome symptoms ease when you stop exercising, but return with activity unless training changes or surgery address it.

How long does recovery from a fasciotomy take?

Fasciotomy wounds are usually closed or skin-grafted within about a week. Recovery of function takes weeks to months and depends on how much muscle and nerve damage occurred. After fasciotomy for chronic exertional compartment syndrome, many athletes return to sport in 6 to 12 weeks.