Anterior compartment syndrome (ACS) is a complication of damage in the front lateral portion of the lower leg that can cause moderate to severe muscle and nerve damage. Let’s look at the anatomy of the compartment, describe what the syndrome is, how to identify it and what can cause it.
Anatomy
The anterior compartment is a section of the lower leg between the knee and ankles. It is bounded by the tibia and fibula bones on either side,, the tough interosseous membrane between these two bones forms the back wall and a tough outer membrane just below the skin forms the front wall. The anterior compartment contains these four muscles:
- Tibialis anterior
- Extensor digitorum longus
- Extensor hallucis longus
- Fibularis tertius
What is Anterior Compartment Syndrome
The bones as well as the tough membranes forming and back and front walls do not stretch easily when there is any type of swelling within the compartment. As a result, any fluid accumulation that results from let’s say, a pulled muscle,, does not result in swelling as easily as it does in other areas of the body. Instead, there is an increase in pressure as fluid increases from the inflammation.
The result of that increased pressure is that the thinner walled veins and lymph vessels that are contained within the compartment tend to gradually collapse as the pressure increases from an inflammation. The thicker walled arteries however, continue to deliver blood. This results in further increase in fluid in the anterior compartment as blood gets in faster than it can get out. This vicious cycle can continue until the pressure is so severe that it can eventually collapse the arteries as well.
At this point, all of the tissues become starved for oxygen and tissue damage spreads to include all of the muscles, nerves and other tissues in the compartment. This tissue damage resulting from oxygen starvation can be quite severe and can progress to the point of a medical emergency.
Identification
ACS needs to be differentiated from its much more mild ‘shin splint’ counterpart. Shin splints are a fairly vaguely defined term referring to pain in the shin region, typically resulting from pulled muscles. Pulled muscles in the anterior compartment can cause pain and even some degree of pressurization and circulation imbalance. The key feature which differentiates anterior compartment pulled muscles from the ‘syndrome’ is a circulation imbalance that gets to the point of collapsing the arteries.
At this stage, you have anterior compartment syndrome and there will be no pulses in the region. The collapsed arteries will also cause the region to be pale, quite the opposite from most painful areas which tend to be more red than normal color. Pain will not be influenced as you would normally expect with analgesics due to the degree and type of tissue damage. Parastesias or tingling will begin in the anterior compartment region or possibly into the foot once the nerves become damaged from lack of oxygen. Paralysis will ultimately occur in the muscles within the compartment and further down into the foot as a result of oxygen starved nerve damage and to some degree even muscle cell death.
Causes
While ACS is most directly the result of a greater than normal amount of damage in an area which cannot tolerate extensive swelling, other factors can contribute to its frequency or severity. These include items that fall roughly into the following categories: 1) increased rate of damage; 2) decreased rate of repair; 3) impaired inflammation regulation.
1) Increased rate of damage – If damage is happening to the muscles in the anterior compartment faster than it can be repaired in a person with normal, healthy repair processes, the amount of damage and associated inflammation will accumulate until the syndrome threshold is reached. Factors that can increase the rate of damage include excessive strain from unusual activities (trapeze artists hanging from feet, marching through deep mud, lots of lateral kicks, trauma & severe lateral ankle sprain). Abnormal strain can also be placed on muscles in the compartment with people doing relatively normal activities when they have imbalanced muscles in the region. The imbalances increase the amount of strain and tissue damage relative to the actual stress placed on the muscle.
2) Decreased Rate of Repair – People who experience relatively normal amounts of strain but decreased rates of repair compared to optimum, will also accumulate more active tissue damage and associated swelling than they should. Many factors influence rates of repair including: suboptimal essential nutrient status of any of the nutrients used in muscle repair (essential amino acids, vitamin C, magnesium, zinc, etc.); drug side effects that inhibit or compete with tissue repair or essential nutrients; abnormal sugar regulation (diabetes, hypoglycemia); other metabolic and disease states).
3) Impaired Inflammation Regulation – Inflammation is a normal part of any repair process. In some people however, there is inflammation disproportionate to the amount of damage they receive. This can happen when: they do not produce enough cortisone (adrenal fatigue, low cholesterol, statin drug side effect); they take in too many inflammation producing chemicals (omega 6 fats, air pollution, non-organic foods, drug reaction, etc.); allergy systemic response (food allergies, ‘hay fever’, etc.),
As with so many health conditions, it is frequently not a matter of just one cause. It is important to explore as many possible contributing factors as you can with your healthcare provider to see which ones are involved and to what degree each is involved. It is not unusual to find that 4-8 different factors involved, each contributing to your specific syndrome profile. Some factors contribute just a little to your ACS, while others contribute a lot. That is why the treatments that worked for your friend or neighbor, might have little to no effect for you. The key is to diagnose the causes first, then treat.
Images courtesy of
1, 2, 4 – Microsoft, used with permission
3 – john Wallman