Excerpt from Compartment Syndromes

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Background

Chronic exertional compartment syndrome (CECS) is a condition in athletes that can occur from repetitive loading or exertional activities. It can occur in any compartment of the extremities, but it is most commonly recognized in the lower legs. Even though physicians have been aware of CECS symptoms since the early part of the 20th century, it was not until the late 1950s that the first reports on CECS were documented. Unlike acute compartment syndrome, which usually results from trauma, the pathophysiology of CECS is not well understood and multiple theories and mechanisms have been suggested as to its etiology.

Mavor was the first to describe the entity in 1956 in a patient experiencing recurrent anterior leg pain with exertion associated with herniation of the muscle and numbness of the affected extremity.

CECS is characterized by exercise-induced pain which is relieved by rest. In severe cases, weakness and paresthesia may accompany the pain and may be the result of ischemic changes within the compartment.

In 1975, Reneman defined the clinical manifestations of this condition and identified increased intracompartmental pressure as the cause. Case studies of CECS in the forearm, thigh, and gluteal regions have been described but are rare. The lower leg remains the most common site of involvement. CECS is a not uncommon problem among runners and is frequently misdiagnosed.

Frequency

United States

True prevalence is uncertain; however, one study found a 14% prevalence rate of anterior CECS in individuals who reported lower leg pain. Males and females are affected equally, with bilateral involvement common. CECS usually occurs in well-conditioned athletes younger than 40 years. Athletes with CECS who markedly increase their training are at risk of developing exacerbation, as are inactive patients who initiate rigorous training.

International

The true prevalence is unknown.

Functional Anatomy

A firm grasp of lower extremity anatomy is central to understanding the pathophysiology, diagnosis, and treatment of CECS.

The lower leg is divided into 4 compartments. A fifth compartment has recently been documented, but the clinical significance of this has yet to be established. The compartments are as follows:

• Anterior: This consists of the tibialis anterior, extensor digitorum longus, extensor hallucis longus, and peroneus tertius. The borders of this compartment are the tibia, fibula, interosseous membrane, and anterior intermuscular septum.



• Lateral: The lateral compartment includes the peroneus longus and brevis. Within the compartment lie the common peroneal nerve and its superficial and deep branches. This compartment is bordered by the anterior intermuscular septum, the fibula, the posterior intermuscular septum, and the deep fascia.



• Superficial posterior: The superficial posterior compartment is surrounded by the deep fascia of the leg and contains the gastrocnemius, soleus, and plantaris.



• Deep posterior: The deep posterior compartment lies between the tibia, fibula, deep transverse fascia, and interosseous membrane. The muscles within the compartment are the flexor digitorum longus, flexor hallucis longus, popliteus, and tibialis posterior. Also within this compartment lie the posterior tibial artery and vein and the tibial nerve.



• Tibialis posterior: This compartment (a subdivision of the deep posterior compartment) is newly described and consists of the tibialis posterior, which has recently been shown to have its own fascial layer.

Typically, the anterior compartment of the leg is the most frequently affected compartment.

Sport Specific Biomechanics

CECS pain is thought to derive from the same pathologic processes that cause pain in acute compartment syndrome, ie, compromise of the vascular supply, which leads to myoneural ischemia. Various mechanisms are suggested as to the cause of this tissue ischemia. These mechanisms include arterial spasm, capillary obstruction, arteriovenous collapse, or venous outflow obstruction. However, an MRI study recently conducted by Amendola et al showed that significant tissue ischemia does not develop.

Other theories have been proposed and suggest that muscle hypertrophy and/or fascial inflexibility is the origin of pain in patients with CECS. However, not all athletes with muscle hypertrophy develop compartment syndrome. CECS is associated with increased pressure in muscles at rest. Transient increases in compartmental pressure have been demonstrated in patients as a normal response to exercise. These pressures usually normalize within 5 minutes after cessation of exercise. In patients with CECS, pressures may remain elevated for 30 minutes or longer.

Another theory, known as the mechanical damage theory, states that exercise results in myofibril damage and release of protein-bound ions. Frequent damage, such as that occurring in the anterior compartment of runners, results in an increased release of ions, increased osmotic pressure, and decreased blood flow within the compartment.

Despite these various explanations for the cause of pain in CECS, no single theory has been overwhelmingly accepted. Further investigation is needed, including the relationship between pain and compartment metabolites.

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