Intraoperative Duplex and Functional Popliteal Entrapment Syndrome: Strategy for Effective Treatment
Article Outline
Functional popliteal entrapment syndrome (FPES) was first described by Rignault and colleagues in 1985 (Int. Angiol. 1985;4:341–343). This syndrome results from compression of the popliteal artery by a hypertrophied medial head of the gastrocnemius muscle with no other identifiable anatomical abnormality. The incidence, significance, natural history, and appropriate treatment of this syndrome remain controversial. We present three cases of FPES where intraoperative positional duplex scans guided gastrocnemius muscle resection and confirmed appropriate resection. Additionally, B-mode duplex obtained during one of the cases demonstrated intimal changes consistent with repetitive vessel trauma. All patients had resolution of their claudication and normal physiological testing postoperatively.
Functional popliteal entrapment syndrome (FPES) is an unusual cause of claudication and is diagnosed when no anatomical abnormality is found to account for the clinical and radiographic manifestations of popliteal entrapment syndrome. The management of FPES depends on the amount of arterial damage caused by repetitive trauma to the vessel. In the early stages of FPES, there is minimal arterial damage and partial resection of the medial head of the gastrocnemius muscle is effective. Once there is a significant stenosis or occlusion of the popliteal artery, bypass is required in addition to release of the compressive portion of the medial head of the gastrocnemius muscle. We present three cases of FPES, one occurring in a young, healthy male, another bilaterally in a young, healthy female, and the third in a fit, active male. As we will demonstrate in these three cases utilizing intraoperative duplex, the proper limits of resection of the medial head of the gastrocnemius were defined, thereby achieving surgical correction on the initial operation and limiting the risk of inadequate resection and continued symptoms. Additionally, intraoperative direct B-mode analysis of the popliteal arterial wall can assess the popliteal artery for intimal changes that would be consistent with the repetitive trauma seen in FPES.
Case Report 1
A 48-year-old male presented to our vascular surgery clinic with a 4-year history of bilateral knee pain and left leg numbness when running. He had previously been evaluated by the orthopedic surgery and the neurology services, with no abnormalities identified on lumbar spine magnetic resonance imaging as well as a normal nerve conduction study. He was then sent to the Vascular Surgery Service, where he had a normal (>1) ankle-brachial index (ABI), but an exercise treadmill test demonstrated that his systolic ankle pressures went from a baseline of 149 to 91 mm Hg following exercise. Subsequent angiography demonstrated significant narrowing of the left popliteal artery with active dorsiflexion of the left foot, consistent with popliteal entrapment syndrome. He had no other significant medical or surgical history.
Intraoperatively, he was noted to have no abnormal anatomical pathology to account for his popliteal entrapment syndrome and underwent resection of the medial head of the gastrocnemius muscle for his FPES. After what was felt by the vascular surgeon to be an adequate clinical resection, provocative maneuvers with intraoperative duplex were performed. The duplex demonstrated normal velocities in the neutral position; however, with active dorsiflexion of the foot, sonography of the popliteal artery demonstrated a loss of the Doppler signal. Further resection of the medial head of the gastrocnemius was performed utilizing spectral duplex to confirm unchanged systolic velocities measured through the popliteal artery at rest and with plantar and dorsiflexion. Additionally, he was noted to have intimal changes within the wall of his popliteal artery as seen with B-mode duplex scanning of the popliteal artery (Fig. 1). He underwent an uneventful postoperative course with strong palpable and audible triphasic Doppler signals in his posterior tibial, dorsalis pedis, and anterior tibial arteries at baseline and with provocative maneuvers. He was ambulating on postoperative day 2 and had resolution of symptoms with subjective and objective confirmation at all of his follow-up visits.
Fig. 1
B-mode duplex surveillance at the conclusion of the case, demonstrating changes in the popliteal arterial wall secondary to repetitive trauma.
Case Report 2
A previously healthy 38-year-old female was referred to our vascular surgery clinic with complaints of bilateral calf pain after ambulating 100 feet. The symptoms had been present intermittently for 5 years, but over the 3 months prior to her presentation the symptoms had increased and limited her ambulation to 100 feet. Her medical history was noncontributory; however, she had a 10 pack-year smoking history and a family history significant for peripheral vascular disease. Upon initial examination she had a normal pulse exam, but with active plantar flexion there was obliteration of her pedal pulses bilaterally. Duplex ultrasonography also demonstrated consistent decreases in peak systolic velocities with active plantar flexion, the left being significantly worse than the right. She subsequently underwent computed tomography (CT) angiography, which demonstrated no anatomical abnormalities of her popliteal arteries or popliteal musculature. Standard contrast angiography with provocative maneuvers was performed, which was consistent with bilateral popliteal entrapment syndrome with arterial occlusion during plantar flexion, greatest on the left (Fig. 2) compared to the right. She was subsequently taken to the operating room, where she underwent left popliteal exploration. Intraoperatively, she was noted to have no aberrant anatomical pathology to account for her popliteal entrapment syndrome (i.e., PES I–V). This was consistent with FPES (Fig. 3). A partial resection of the medial head of the gastrocnemius muscle was performed. Clinically, the myectomy was felt to be adequate, with no palpable compressive portions on the artery. Duplex sonography was performed over her popliteal artery, demonstrating that the gastrocnemius resection was adequate as there was no change in maximal duplex velocities within the popliteal artery with provocative maneuvers. Additionally, there were no changes within the arterial wall of the artery on B-mode surveillance of the popliteal artery. She was discharged on postoperative day 2 without complications and seen in follow-up with resolution of her symptoms on the left but with claudication of her right leg, which now limits her lifestyle activities.
Fig. 2
Cutoff of flow through popliteal arteries bilaterally with plantar flexion.
Fig. 3
Posterior exploration demonstrating no anatomical abnormality but hypertrophy of the gastrocnemius muscle (left). Resection of the medial head of the gastrocnemius muscle (right).
Upon exploration of her right popliteal artery, she was found to have no anatomical abnormality, again consistent with FPES, and subsequently underwent clinical resection of the medial head of the gastrocnemius muscle. Duplex sonography after this resection demonstrated continued compression of the popliteal artery with provocative maneuvers despite an appropriate clinical resection (Fig. 4). Further resection of the medial head of the gastrocnemius muscle was performed, and subsequently there was no decrease in the systolic velocities or waveform changes on duplex with provocative maneuvers. She had an uneventful recovery, clinical resolution of symptoms, and objective duplex confirmation of normal velocities with provocative maneuvers postoperatively.
Fig. 4
Duplex at rest (top left) with decrease in flow with maximal dorsiflexion after initial clinical resection (top right). Further myectomy with no change in flow through all ranges of motion (bottom left). Exercise ABI at follow-up.
Case Report 3
The third patient was a 53-year-old male who presented with exercise-induced claudication. Upon evaluation he was noted to have progressively worsening symptoms that limited his ability to run. Exercise ABIs demonstrated a fall from 1 to 0.66 after 2 min, with associated claudication symptoms during the testing. An arteriogram confirmed the findings of total compression of the above-knee popliteal artery. He was then taken for popliteal exploration, and no anatomical abnormality was detected. A baseline duplex was obtained, and then he underwent initial myectomy of the medial head of the gastrocnemius with follow-up spectral duplex analysis. Given the findings of continued compression as evidenced by significant reduction in the peak systolic velocities, an additional resection of the gastrocnemius muscle was performed, with resultant stability of the maximal systolic velocities throughout all ranges of motion and provocative maneuvers. Postoperatively, he did well and had resolution of his symptoms clinically on subsequent follow-up.
Discussion
In 1985, Rignault et al.1 first described FPES. Hypertrophy of the gastrocnemius muscle was a consistent finding in this series. Levien and Lewis2 further described functional popliteal entrapment and added it to the standard popliteal entrapment classification as type VI entrapment. In 1992, Turnipseed and Pozniak3, 4 described the common findings seen with FPES. They found that there were no symptoms in the neutral position and that dorsiflexion caused compression of popliteal vessels by a hypertrophic gastrocnemius muscles. These symptoms resolved after partial resection of the medial head of the gastronemius muscle. They hypothesized that this entrapment occurs due to compression of the popliteal neurovascular bundle against the lateral angle of the soleal sling and lateral condyle of the tibia. The incidence of FPES is unknown, but in one series 0.25% of all patients referred for lower limb pain were felt to have FPES.5
The classification of popliteal entrapment is based upon the embryological development of the popliteal artery. Normally, the popliteal artery forms after the migration of the medial head of the gastrocnemius muscle. If the artery forms prematurely, the medial migration of the gastrocnemius will displace the artery medially. When the gastrocnemius inserts normally, type I entrapment occurs; but when there is abnormal insertion of the gastrocnemius muscle onto the femur, a type II entrapment occurs. When mesodermal remnants of the popliteal artery are left within the popliteal fossa, an abnormal slip of muscle or fibrous band occurs and may compress the popliteal artery (type III). Type IV occurs when the embryological blood supply persists deep to the popliteus muscle and the artery is compressed in this location. Type V occurs with any of the above anatomical abnormalities and compression involving both the popliteal artery and vein.
FPES occurs when there is none of the aforementioned anatomical abnormalities to account for the compression of the popliteal artery. This type may be secondary to gastrocnemius hypertrophy, compression of the popliteal artery as it passes through the soleal sling, or compression against the lateral condyle of the tibia with contraction of the gastrocnemius muscle. The injury that occurs with functional popliteal entrapment will lead to the same changes in the vessel wall as do types I–V. The diagnosis is dependent on provocative maneuvers to assess for a decrease in pedal blood flow. How much muscle to resect in order to ensure that there is no further compression and repetitive trauma to the popliteal artery has yet to be determined.
Our workup of functional popliteal entrapment is described in Fig 5. Initially, a thorough history and physical exam utilizing provocative maneuvers (active/passive plantar and dorsiflexion) should be performed. Noninvasive exercise ABIs should next be obtained and, if found to be less than 0.9, CT or magnetic resonance angiography performed to identify types I–V PES. If no anatomical abnormality is present, an angiogram with provocative maneuvers should be obtained to identify the exact area of popliteal artery compression. When compression is present, exploration should then be performed with the use of intraoperative duplex to guide the extent of gastrocnemius resection.
Fig. 5
Workup of FPES. MRA, magnetic resonance angiography.
In our case series, the three patients were found to have no anatomical abnormality either with preoperative imaging or with intraoperative visual inspection of the artery. With the aid of intraoperative duplex sonography, proper limits of resection were obtainable without the need for contrast angiography or postoperative imaging. After initial myectomy, there was no palpable or visual compression of the popliteal artery. With the guidance of intraoperative duplex sonography, the first case demonstrated a need for further resection after the initial clinical resection. In the second case, intraoperative duplex was able to demonstrate that the resection was adequate to prevent further symptoms from a functional popliteal entrapment on the left and aided with appropriate resection on the right. The final patient initially had an appropriate clinical resection, but intraoperative duplex aided in defining a small amount of muscle from the medial head of the gastrocnemius muscle that was needed for a complete resection.
In addition to confirmation of appropriate resection in all cases, there was an intimal change seen with the first case (Fig. 1). This intimal change demonstrates that changes will occur within the popliteal vasculature with a functional popliteal entrapment. These intimal changes will occur through repetitive trauma to the artery and progress through three different stages. The stages occur progressively through neovascularization and inflammatory cell infiltrate and deposition, leading to destruction of the vessel wall by fibrosis and collagen deposition. With each muscle contraction the artery is stressed and gradually becomes more compromised. The classification parallels the extent of the vessel wall, with stage 1 involving the adventitia, stage 2 the media, and stage 3 the intimal layer.2
The cases reported here support the use of intraoperative duplex when performing a myectomy in functional popliteal entrapment as an adjunct to determining how much of the medial head of the gastronemius muscle to resect. This case series suggests that clinical assessment intraoperatively is not a good indicator for adequacy of muscle resection. With inadequate resection the patients may continue to have symptoms and repetitive trauma to the arterial wall.
References
- . The “functional” popliteal entrapment syndrome. Int Angiol. 1985;4:341–343
- . Popliteal artery entrapment syndrome. Semin Vasc Surg. 2003;16:223–231
- . Popliteal entrapment as a result of neurovascular compression by the soleus and plantaris muscles. J Vasc Surg. 1992;15:285–293
- . Functional popliteal artery entrapment syndrome: a poorly understood and often missed diagnosis that is frequently mistreated. J Vasc Surg. 2009;49:1189–1195
- . Popliteal entrapment syndrome: anatomic or functional syndrome. Clin J Sport Med. 2004;14:8–12
The investigators have adhered to the policies for protection of human subjects as prescribed in 45 CFR 46.
The views expressed are those of the author(s) and do not reflect the official policy of the Department of the Army, the Department of Defense, or the U.S. government.
PII: S0890-5096(09)00322-7
doi:10.1016/j.avsg.2009.07.036
© 2010 Published by Elsevier Inc.
