Fascial compartment
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On the human body, the limbs can be divide into segments, such as the arm and the forearm of the upper limb, and the thigh and the leg of the lower limb.
If these segments are cut transversely, it is apparent that they are divided into multiple sections. These are called fascial compartments, and are formed by tough connective tissue septa.
These compartments usually have a separate nerve and blood supply to their neighbours. The muscles in each compartment will often all be supplied by the same nerve.
Compartment syndrome
Knowledge of these compartments not only simplifies the learning of innervation, it is also important in situations where pressure can build up in one compartment and potentially damage the contents.
This problem is called compartment syndrome and can happen acutely (sometimes caused by a fracture) or gradually, as with an athlete's overuse of a muscle.
Because the connective tissue that defines the compartment 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. Increased pressure within the compartment compresses the nerves, and also decreases blood perfusion. The pressure in the capillaries is approximately 30mm Hg. If the pressure in the compartment rises above this level the blood supply to the muscles can be completely cut off leading to death of the tissue in the compartment. This is a medical emergency requiring immediate treatment by fasciotomy to allow the pressure to return to normal. Because the pressure in the large large blood vessles of the limbs is much greater than the compartment pressure required to cause death of the tissue, a patient whose muscles are dying from compartment syndrome, and who is in danger of losing their limb will usually have intact pulses. Severe pain is the most common symptom of an accute compartment syndrome.
When compartment syndrome is caused by from repetitive heavy use of the muscles, as in a runner, 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 muscle.
While CCS was first identified in the 1980s, it has been increasingly recognized as a significant source of chronic leg pain. A common indicator of the condition is muscle fatigue and pain in the calf region after sustained physical exercise (such as running). Once the exercise is stopped, the pain gradually disappears.
CCS can be tested for using by gauging the pressure within the muscle compartments. If the pressure is sufficiently high, a fasciotomy may be required.
Fascial compartments of the body
The thigh is usually divided into three compartments:
- Anterior - supplied by the femoral nerve, contains the knee extensors and hip flexors.
- Medial - supplied by the obturator nerve, contains the hip adductors.
- Posterior - supplied by the sciatic nerve, contains the knee flexors and hip extensors.
The (lower) leg is divided into three compartments also:
- Anterior - supplied by the deep peroneal nerve and anterior tibial artery, contains the dorsiflexors.
- Lateral - supplied by the superficial peroneal nerve, contains the evertors of the foot.
- Posterior - supplied by the tibial nerve, contains the plantar flexors.
The (upper) arm is divided into:
The forearm is divided into two compartments: