Evaluation of popliteal artery entrapment in healthy individuals

Popliteal artery entrapment syndrome (PAES) is an uncommon lower leg pain
syndrome predominantly affecting young athletes. It refers to a condition in
which the popliteal artery is compressed by calf muscles and is classified as
one of the vascular causes of *exercise-induced lower leg pain
syndromes* (ELP). PAES patients most often suffer from the functional type
(fPAES), where too bulky well-developed muscles compress the popliteal artery.
In contrast, a small portion of patients have symptoms due to an abnormal
position of the artery relative to the muscles leading to vascular compression
(anatomical PAES).
Due to a reduction in arterial perfusion and lack of oxygen, individuals with
symptomatic PAES often experience calf cramping, pain, muscle weakness and
tingling sensations during exertion. The pattern of these symptoms may resemble
other types of ELP such as the deep posterior type of chronic exertional
compartment syndrome (dp-CECS). During dp-CECS, symptoms are thought to occur
from elevated muscle pressures that can be measured using an invasive pressure
analysis.
Discrimination between PAES and dp-CECS may be exceedingly difficult. As both
PAES and CECS are relatively unknown syndromes, rates of underdiagnosis and
protracted diagnostic delay are high. It is important that patients are
correctly diagnosed in order to institute the best treatment. There is a direct
relation between diagnostic delay and treatment outcome. Moreover, untoward
events such as irreversible damage to the arterial wall in PAES with subsequent
acute occlusion must be prevented at all times. Therefore, the diagnostic
regimen should be optimized.
If PAES is suspected by a patient history while the compartment pressure is
inconclusive, duplex ultrasonography (DUS) during lower leg provocative tests
(pointing, active plantar flexion) is indicated. In addition, a walking test
with Ankle-Brachial Index (ABI) measurement after a provocative exercise is
performed, allowing for observation of the patient. Dynamic magnetic resonance
imaging (MRI) during provocation may help to distinguish between a case of
anatomical and functional PAES.
There is a strong need for identification of a diagnostic gold standard for
fPAES. However, earlier DUS studies have demonstrated that compression of the
popliteal artery is quite common in healthy individuals not having any lower
leg symptoms (up to 50%!). Whether these healthy asymptomatic individuals with
abnormal DUS images may also show popliteal artery compression during a dynamic
MRI is unknown.

To investigate in healthy individuals not having ELP whether DUS and dynamic
MRI may reveal a compressed popliteal artery in rest and during provocative
testing (pointing, plantar foot flexion).

Descriptive study with exploratory elements in which healthy volunteers undergo
a DUS and a dynamic MRI. A walking test with Ankle-Brachial Index (ABI) is
performed to rule out other causes of ELP. There is one study arm, no
comparator and no randomisation.

Individuals will complete a 10 minute symptom questionnaire and a questionnaire
to ensure safety of the MRI-scan. They will walk for 5 minutes on a treadmill
while being observed by a vascular technician. They will then undergo a
15-minute ultrasound analysis of both popliteal fossae in prone position. The
MRI analysis will last 45-60 minutes.
There is no harm associated with a DUS or walking test. Provided a volunteer
does not have implants and is not claustrophobic, an MRI is not harmful. All
tests will be planned during one day, ideally within a 2-hour time frame.
Subjects will receive ¤50 for a complete participation. Other than that, they
will not benefit from this study.