Compartment syndrome

**Compartment syndrome** is a condition in which increased pressure within one of the body's anatomical compartments results in insufficient blood supply to tissue within that space. There are two main types: acute and chronic. Compartments of the leg or arm are most commonly involved.

Symptoms of acute compartment syndrome (ACS) can include severe pain, poor pulses, decreased ability to move, numbness, or a pale color of the affected limb. It is most commonly due to physical trauma such as a bone fracture or crush injury. It can also occur after blood flow returns following a period of poor blood flow. Diagnosis is generally based upon a person's symptoms. Treatment is by surgery to open the compartment completed in a timely manner. If not treated within six hours, permanent muscle or nerve damage can result.

In chronic compartment syndrome, there is generally pain with exercise. Other symptoms may include numbness. Symptoms typically resolve with rest. Common activities that trigger chronic compartment syndrome include running and biking. Generally, this condition does not result in permanent damage. Other conditions that may present similarly include stress fractures and tendinitis. Treatment may include physical therapy or—if that is not effective—surgery.

Acute compartment syndrome occurs in about 3% of those who have a midshaft fracture of the forearm. Rates in other areas of the body and for chronic cases are unknown. The condition more often occurs in those under the age of 35 and in males. Compartment syndrome was first described in 1881 by Richard von Volkmann. Untreated, acute compartment syndrome can result in Volkmann's contracture.

## Signs and symptoms

Acute compartment syndrome can develop after traumatic injuries, such as in automobile accidents or dynamic sporting activities – for example, a severe crush injury or an open or closed fracture of an extremity. Rarely, ACS can develop after a relatively minor injury, or due to another medical issue. The legs and the forearms are the most frequent sites affected by compartment syndrome. Other areas of the body such as thigh, buttock, hand, and foot can also be affected.

### Acute

There are five characteristic signs and symptoms related to acute compartment syndrome: pain, paraesthesia (reduced sensation), paralysis, pallor, and pulselessness. Pain and paresthesia are the early symptoms of compartment syndrome.

**Common**
* **Pain** – A person may experience disproportionate to the findings of the physical examination. This pain may not be relieved by strong analgesic medications. The pain is aggravated by passively stretching the muscle group within the compartment. However, such pain may disappear in the late stages of the compartment syndrome. The role of local anesthesia in delaying the diagnosis of compartment syndrome is still being debated.
* **Paresthesia** (altered sensation) – A person may complain of "pins & needles", numbness, and a tingling sensation. This may progress to loss of sensation (anesthesia) if no intervention is made.

**Uncommon**
* **Paralysis** – Paralysis of the limb is a rare, late finding. It may indicate both a nerve or muscular lesion.
* **Pallor and pulselessness** – A lack of pulse rarely occurs in patients, as pressures that cause compartment syndrome are often well below arterial pressures. Absent pulses only occur when there is arterial injury or during the late stages of the compartment syndrome, when compartment pressures are very high. Pallor can also result from arterial occlusion.

The limb affected by compartment syndrome is often associated with a firm, wooden feeling on deep palpation.

### Chronic

The symptoms of chronic exertional compartment syndrome, CECS, may involve numbness, tingling, or pain described as burning, cramping, sharp, or stabbing. This pain can occur for months, and in some cases over a period of years, and may be relieved by rest. Moderate weakness in the affected region can also be observed. These symptoms are brought on by exercise and consist of a sensation of extreme tightness in the affected muscles followed by a painful burning sensation if exercise is continued. After exercise is ceased, the pressure in the compartment will decrease within a few minutes, relieving painful symptoms. Symptoms will occur at a certain threshold of exercise which varies from person to person but is rather consistent for a given individual. This threshold can range anywhere from 30 seconds of running to about 10–15 minutes of running. CECS most commonly occurs in the lower leg, with the anterior compartment being the most frequently affected compartment. Foot drop is a common symptom of CECS.

### Complications

Failure to relieve the pressure can result in the death of tissues (necrosis) in the affected anatomical compartment, since the ability of blood to enter the smallest vessels in the compartment (capillary perfusion pressure) will fall. This, in turn, leads to progressively increasing oxygen deprivation of the tissues dependent on this blood supply. Without sufficient oxygen, the tissue will die. On a large scale, this can cause Volkmann's contracture in affected limbs, a permanent and irreversible process. Other reported complications include neurological deficits of the affected limb, gangrene, and chronic regional pain syndrome. Rhabdomyolysis and subsequent kidney failure are also possible complications. In some case series, rhabdomyolysis is reported in 23% of patients with ACS.

## Causes

### Acute

The most common cause of acute compartment syndrome (ACS) is fracture of a bone, which accounts for 69% to 75% of the reported cases. Importantly, there is no difference in the incidence of compartment syndrome between open and closed fractures. Leg compartment syndrome is found in 2% to 9% of tibial fractures. Direct injury to blood vessels can lead to compartment syndrome by reducing the downstream blood supply to soft tissues. This reduction in blood supply can cause a series of inflammatory reactions that promote the swelling of the soft tissues. Such inflammation can be further worsened by reperfusion therapy. Because the fascia layer that defines the compartment of the limbs does not stretch, a small amount of bleeding into the compartment, or swelling of the muscles within the compartment, can cause the pressure to rise greatly. Intravenous drug injection, casts, prolonged limb compression, crush injuries and eschar from burns can also cause compartment syndrome. Patients on anticoagulant therapy have an increased risk of bleeding into a closed compartment.

Abdominal compartment syndrome occurs when the intra-abdominal pressure exceeds 20 mmHg and abdominal perfusion pressure is less than 60 mmHg. This disease process is associated with organ dysfunction and multiple organ failures. There are many causes, which can be broadly grouped into three mechanisms: primary (internal bleeding and swelling); secondary (vigorous fluid replacement as an unintended complication of resuscitative medical treatment, leading to the acute formation of ascites and a rise in intra-abdominal pressure); and recurrent (compartment syndrome that has returned after the initial treatment of secondary compartment syndrome).

There have been cases of compartment syndrome associated with hypothyroidism.

### Chronic

See also: Shin splints
When compartment syndrome is caused by repetitive use of the muscles, it is known as chronic compartment syndrome (CCS). This is usually not an emergency, but the loss of circulation can cause temporary or permanent damage to nearby nerves and muscles.

A subset of chronic compartment syndrome is chronic exertional compartment syndrome (CECS), often called exercise-induced compartment syndrome (EICS). Oftentimes, CECS is a diagnosis of exclusion. CECS of the leg is a condition caused by exercise which results in increased tissue pressure within an anatomical compartment due to an acute increase in muscle volume – as much as 20% is possible during exercise. When this happens, pressure builds up in the tissues and muscles causing tissue ischemia. An increase in muscle weight will reduce the compartment volume of the surrounding fascial borders and result in an increased compartment pressure. An increase in the pressure of the tissue can force fluid to leak into the interstitial space (extracellular fluid), leading to a disruption of the micro-circulation of the leg. This condition occurs commonly in the lower leg and various other locations within the body, such as the foot or forearm. CECS can be seen in athletes who train rigorously in activities that involve constant repetitive actions or motions.

## Pathophysiology

In a normal human body, blood flow from the arterial system (higher pressure) to venous system (lower pressure) requires a pressure gradient. When this pressure gradient is diminished, blood flow from the artery to the vein is reduced. This causes a backup of blood and excessive fluid to leak from the capillary wall into spaces between the soft tissues cells, causing swelling of the extracellular space and a rise in intracompartmental pressure. This swelling of the soft tissues surrounding the blood vessels compresses the blood and lymphatic vessels further, causing more fluid to enter the extracellular spaces, leading to additional compression. This worsening cycle can eventually lead to a lack of sufficient oxygen in the soft tissues (tissue ischemia) and tissue death (necrosis). Tingling and abnormal sensation (paraesthesia) can begin as early as 30 minutes from the start of tissue ischemia and permanent damage can occur as early as 12 hours from the onset of the inciting injury.

## Diagnosis

Compartment syndrome is a clinical diagnosis, meaning that a medical provider's examination and the patient's history usually give the diagnosis. Apart from the typical signs and symptoms, measurement of intracompartmental pressure can also be important for diagnosis. A transducer connected to a catheter is inserted 5 cm into the zone of injury. A pressure higher than 30 mmHg of the diastolic pressure in a conscious or unconscious person is associated with compartment syndrome. Fasciotomy is indicated in that case. For those patients with low blood pressure (hypotension), a pressure of 20 mmHg higher than the intracompartmental pressure is associated with compartmental syndrome.

Chronic exertional compartment syndrome is usually a diagnosis of exclusion, with the hallmark finding being absence of symptoms at rest. Measurement of intracompartmental pressures during symptom reproduction (usually immediately following running) is the most useful test. Imaging studies (X-ray, CT, MRI) can be useful in ruling out the more common diagnoses.

## Treatment

### Acute

Any external compression (tourniquet, orthopedic casts or dressings applied on the affected limb) should be removed. Cutting of the cast will reduce the intracompartmental pressure by 65%, followed by 10 to 20% pressure reduction once padding is cut. After removal of the external compression the limb should be placed at the level of the heart. The vital signs of the patient should be closely monitored. If the clinical condition does not improve, then fasciotomy is indicated to decompress the compartments. An incision large enough to decompress all the compartments is necessary. This surgical procedure is performed inside an operating theater under general or local anesthesia. The timing of the fasciotomy wound closure is debated. Some surgeons suggest wound closure would done seven days after fasciotomy.

### Chronic

Treatment for chronic exertional compartment syndrome can include decreasing or subsiding exercise and/or exacerbating activities, massage, non-steroidal anti-inflammatory medication, and physiotherapy. Chronic compartment syndrome in the lower leg can be treated conservatively or surgically. Conservative treatment includes rest, anti-inflammatory medications, and manual decompression. Elevation of the affected limb in patients with compartment syndrome is contraindicated, as this leads to decreased vascular perfusion of the affected region. Ideally, the affected limb should be positioned at the level of the heart. The use of devices that apply external pressure to the area, such as splints, casts, and tight wound dressings, should be avoided. If symptoms persist after conservative treatment or if an individual does not wish to give up the physical activities which bring on symptoms, compartment syndrome can be treated by a surgery known as a fasciotomy.

A US military study conducted in 2012 found that teaching individuals with lower leg chronic exertional compartment syndrome to change their running style to a forefoot running technique abated symptoms in those with symptoms limited to the anterior compartment. Running with a forefoot strike limits use of the tibialis anterior muscle which may explain the relief in symptoms in those with anterior compartment syndrome.

Hyperbaric oxygen therapy has been suggested by case reports – though as of 2011 not proven in randomized control trials – to be an effective adjunctive therapy for crush injury, compartment syndrome, and other acute traumatic ischemias, by improving wound healing and reducing the need for repetitive surgery.

## Prognosis

A mortality rate of 47% has been reported for acute compartment syndrome of the thigh. According to one study the rate of fasciotomy for acute compartment syndrome varied from 2% to 24%. The most significant prognostic factor in patients with acute compartment syndrome is time to diagnosis.

## Epidemiology

In one case series of 164 patients diagnosed with acute compartment syndrome, 69% of the cases had an associated fracture. The authors of that article also calculated an annual incidence of acute compartment syndrome of 1 to 7.3 per 100,000. There are significant differences in the incidence of acute compartment syndrome based on age and gender. With a similar injury pattern, an older patient is more likely to develop ACS than a younger person. Men are ten times more likely than women to develop ACS. The mean age for ACS in men is 30 years while the mean age is 44 years for women.