Iliac artery endofibrosis is a rare but significant condition affecting endurance runners and cyclists. This vascular disorder, often associated with repetitive strain and high-intensity exercise, can compromise blood flow to the legs, causing pain and reduced performance. Understanding the causes, symptoms, and treatment options is essential for athletes aiming to maintain peak performance and avoid long-term complications.
What Is Iliac Artery Endofibrosis?
Iliac artery endofibrosis is a condition in which the inner lining of the external iliac artery thickens abnormally. This thickening reduces the artery’s diameter and elasticity, limiting blood flow to the lower extremities during exercise.
What arteries are involved?
Most cases involve thickening of the external iliac artery. However, sometimes, thickening can affect other vessels, such as the common iliac or femoral arteries. Often, only one side is affected.
Causes of Iliac Artery Endofibrosis
The exact cause of IAE is not fully understood, but several factors contribute to its development:
- Repeated direct mechanical stress leads to the development of fibrous tissue and subsequent narrowing inside the artery. Due to prolonged high-intensity kinking, elite athletes are particularly at risk.
- Elite cyclists are more at risk of the postural positioning of the cyclist, causing arterial kinking.
- Improper bike fits can increase strain and kinking of the artery.
- Enlarged hip flexor muscle, called iliopsoas, can lead to kinking of the iliac artery.
Symptoms of Iliac Artery Endofibrosis
Symptoms occur with exercise and stop almost immediately with rest. The most common symptom is muscle cramping in the buttocks, thighs or calves. Other common symptoms include numbness, tingling, coldness, fatigue, and reduced power output in the lower legs.
Diagnosis of Iliac Artery Endofibrosis
This condition is often underdiagnosed because its symptoms overlap with those of other conditions, such as :
- Exertional compartment syndrome
- Metabolic or muscular conditions such as anaemia or muscle diseases (McArdle’s syndrome)
- Peripheral nerve entrapment of the groin, thigh, calf or sciatica.
Diagnosis requires a thorough assessment, examination, and tests.
Your doctor must examine you before and after exercise to assess your leg muscles, blood supply and nervous system. Sometimes, a whooshing sound can be heard at the pulses of the groin.
Specific tests are invaluable to confirm a diagnosis and include the following:
- ABI (ankle brachial) is performed by measuring the blood pressure in the arms and ankles before and after 5 minutes of intense cycling or running. Then, the ankle pressure is divided by the arm pressure. A normal ratio is 1.0; anything below this indicates decreased blood flow to the legs. Generally, athletes often have normal ABI values at rest, but the ABI in the affected leg typically drops after exercise. A level below 0.5 is highly suggestive of this condition.
- Doppler ultrasound test of the arteries uses sound waves to measure the speed of blood. Generally, the peak speed is much higher after exercise. Sometimes, the ultrasound can reveal thickening or kicking of the arteries.
- MR arthrogram gives a more detailed view of the artery, including its thickness and kinking. This test is often necessary to determine whether surgery is needed.
- Blood tests should be performed to rule out metabolic causes of vascular disease such as diabetes, cholesterol and anaemia.
Treatment Options for Iliac Artery Endofibrosis
Treatment depends on the severity of symptoms and pathology on imaging.
For milder symptoms and pathology, doctors recommend conservative management such as reducing training intensity and duration, adjusting bike setup to minimise hip flexion and physiotherapy to improve hip flexibility and strength with a focus on the larger psoas muscle. Anti-platelet meditation, such as Aspirin, may improve blood flow. Changing sporting activity is another option.
Some examples of optimising bike setup include raising handlebars, bringing the saddle forward to avoid hip hyperflexion, and avoiding pulling upwards on the pedals to prevent psoas muscle hypertrophy.
Surgical Intervention
Open surgery is recommended for more severe symptoms and pathology. Less invasive surgery, such as stents, is not appropriate.
The type of surgery depends on the pathology. If the external iliac artery is kinked by its attachment to the psoas muscle, surgery releases the fibrous tissue. If the external iliac artery is longer than average, surgically shortening it may be necessary. Finally, if symptoms are caused by fibrosis of the vessel wall, an endarterectomy can be performed. This procedure surgically removes the fibrosis from the vessel wall, so blood flow is no longer restricted.
Outcomes of surgery are usually excellent, with a return to high performance within three months.
Other frequently asked questions about Iliac Arterial Endofibrosis
How common is IAE in elite athletes?
It is more common than we think. One study suggested up to 20% of elite athletes have IAE. Other reports indicate skiers, runners, and rowers are at risk.
Final Word from Sportdoctorlondon about Iliac Artery Endofibrosis
Iliac artery endofibrosis is a unique challenge for endurance athletes, particularly cyclists and runners. Early recognition of symptoms and appropriate diagnosis and treatment can prevent long-term complications and allow athletes to continue performing at their best. If you suspect this condition, consult a sports medicine doctor for an assessment to confirm the diagnosis and exclude other causes.
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