Popliteal Artery Entrapment
With the increase in exercise activities that is taking place in the last decade there has been an increase in the presentation of patients with lower limb pain and numbness that has proved to be very difficult to diagnose. Patients have often been to their general practitioner and also a sports physician and they present with exercise associated pain in their muscles with associated numbness from time to time in the sole of the foot and the toes and they are usually younger than patients who present with normal degenerative arterial disease. They have often had many investigations to try and determine the cause and at Melbourne Vascular, we put these patients through resting and exercise associated pressure studies as well as looking at the popliteal arteries with duplex ultrasound to identify whether there is any compression of the popliteal artery with force plantar flexion. Once these test results have been reviewed then a provision diagnosis of popliteal artery entrapment syndrome may be made. The differential diagnosis of this is often chronic executional compartment syndrome and so compartment pressures may be required to clarify the clinical picture.
There are developmental conditions that can lead to popliteal artery entrapment syndrome and these are called anatomical popliteal artery entrapment. If during testing these anatomical entrapments are identified then it is important to proceed with surgical decompression otherwise the artery can be injured chronically to the point of occlusion during the patients lifetime.
If the anatomy otherwise looks normal then the patient will require angiography to determine the point of compression and make a plan for the operation.
Depending on the findings of the investigations the surgical intervention is one of decompression above or below or both. At the operation, the medial head of gastrocnemius (calf muscle) will be divided from the femur (thigh bone) and a section of the muscle removed to make it smaller and allow for more space to be left for the popliteal artery when healing takes place.
If the below knee popliteal artery and popliteal nerve need to be decompressed then this is done by a medial approach on the inner aspect of the calf just below level of the knee. A fasciotomy is performed and then the plantaris is identified and excised and the soleal arch is taken down and all of the fibrosis tissue on its anterior surface is removed. The medial head of gastrocnemius may be debrided further from the below knee approach.
The major considerations in regard to this is that usually doing two areas in the one leg means that one leg is done at a time. This allows for the operated leg to heal with the support of the other leg. It is usually a six-week break between the first and second operations, if the first operation turns out to be effective.
Some of the risks included in surgery are the usual risks of bleeding and infection and wound problems. There are nerves that are close to the operative site and one is the sural nerve at the back of the knee and if injured at the time of surgery it will cause numbness in the back of the lower calf and around the ankle on the outside of the leg. The other area is from the below knee approach where the saphenous nerve filaments are protected but often there is some interruption of function and numbness occurs on the inside of the leg towards the ankle and onto the foot. Occasionally this will recover in a year or two.
The biggest concern in popliteal artery entrapment syndrome and operative intervention is the failure rate of 20% despite all investigations and surgery pointing to the diagnosis and the management having been executed effectively.
Some people will ask the question as to what is the next step if the surgical decompression does not improve their symptoms and no one could give a good explanation of what could be achieved in the future.
The other option for treatment of functional popliteal artery entrapment syndrome is intramuscular injections of Botox into the plantaris and medial head of gastrocnemius muscles. This obviously is a temporary measure.