Forearm arteries entrapment syndrome: A rare cause of recurrent angioaccess thrombosis☆☆☆
Article Outline
Abstract
Entrapment syndrome below or just above the elbow is uncommon. These rare causes of neurologic or vascular entrapment are linked to anomalous anatomical structures. No case of entrapment syndrome has been reported in patients with angioaccess for hemodialysis. We report, for the first time, forearm arteries entrapment in two patients presenting with recurrent angioaccess for hemodialysis thrombosis. Anatomical, radiologic, and surgical features of these uncommon syndromes are discussed. (J Vasc Surg 2001;34:743-7.)
Entrapment syndrome below or just above the elbow is uncommon. With few exceptions, compression at this level involves neurological structures.1, 2, 3, 4 The rare cases of vascular forearm entrapment syndrome described in the literature are linked to an anomalous anatomical structure: the ligament of Struthers.5, 6, 7, 8, 9
We report, for the first time, forearm arteries entrapment in two patients with angioaccess for hemodialysis caused by a pronator teres syndrome and a fibrous arcade of the flexor digitorum superficialis muscle. Both patients presented with recurrent angioaccess failure; no cause was identified except artery occlusion by entrapment in the supinated position. We discuss anatomical, radiologic, and surgical features of these uncommon syndromes.
Case report
Patient 1
A 66-year-old woman was referred to our institution for angiography of her vascular access for dialysis. Two days before, she had acute thrombosis, which was successfully treated with local fibrinolysis and manual aspiration thromboembolectomy. Her angioaccess was a 9-year-old ulnar-to-basilic artery graft (polytetrafluoroethylene [PTFE]), which had already been treated four times for acute thrombosis: one time with surgery (thrombectomy 5 years ago) and three times with local fibrinolysis and manual aspiration thromboembolectomy (4, 3, and 1 years ago).
Angiograms performed by access route during these thromboses did not identify any cause of occlusion and especially no stenosis. A clinical examination performed before the opacification revealed a normally thrilling angioaccess with two large aneurysms at the cannulation site. The arm was set in a supinated position so that an access angiogram could be performed; then, repeated clinical examination showed an access with no thrill perceptible and two flat aneurysms. When the arm was set in pronation, angioaccess thrilled normally anew. An angiogram revealed that the access was patent without significant stenosis. A retrograde puncture of the brachial artery at the elbow was then performed to analyze the arterial tree of the forearm.
Frames were taken in both the pronated and supinated positions. The radial artery was occluded. The ulnar artery was normally patent in pronation but occluded in supination because of an external compression just below its takeoff (Figs 1 and 2).
Fig. 1.
Angioaccess angiogram in pronated position. Radial artery is occluded, and ulnar artery is normally patent with no stenosis. See two large aneurysms at cannulation site.
Fig. 2.
Angioaccess angiogram in supinated position. Ulnar artery is compressed by external structure. Arteriovenous fistula is occluded. Also shown are two aneurysms on PTFE graft.
Underneath this anomalous structure lay the ulnar artery. Because of the two large aneurysms on the PTFE graft (Fig 2, A ) and the absence of ischemic symptoms (an arterial reconstruction was not necessary), angioaccess was ligated, and a new fistula was created at the other forearm.
Patient 2
A 69-year-old man was referred for angiography of his angioaccess for hemodialysis after he had several acute thromboses treated with local fibrinolysis and manual aspiration embolectomy. His angioaccess was a 4-year-old wrist radio cephalic native fistula. This access had already been treated five times for acute thrombosis with local fibrinolysis and manual aspiration embolectomy.
An angiogram performed after these thromboses did not identify any cause of occlusion and especially no stenosis, which is extremely unusual for native fistulas. The clinical examination performed before the arteriography showed a normally thrilling access. The patient did not have any ischemic symptom or pain at rest during dialysis.
Once the patient had lain on the angiographic table, his arm was set along his body in a supinated position. In this position, the angioaccess was flat, with no thrill detectable. The thrill reappeared after a slight rotation of the arm.
The angiogram was obtained by means of a retrograde puncture of the brachial artery at the elbow and showed the access patent without significant stenosis (Fig 3).
Fig. 3.
Angioaccess angiogram in pronated position. This is a normally patent wrist radiocephalic arteriovenous fistula. Ulnar artery is occluded. A, Upper limb arteriography showing high origin of the ulnar artery. B, Angiogram showing that the ulnar artery cannot fill fistula through palmar arch.
The ulnar artery had a high origin and was not able to feed the access in a retrograde way through the palmar arch (Fig 3, A and B ). The radial and interosseous arteries (the interosseous artery has its origin on the radial artery) were normally patent in the pronated position but were occluded in supination by an external compression 2 cm below takeoff of the radial artery (Figs 4 and 5).
Fig. 4.
When forearm is in supinated position, the radial artery is compressed by an external process.
Fig. 5.
Angioaccess angiogram in complete supinated position. Radial artery and arteriovenous fistula are occluded. Cubital artery cannot fill fistula in a retrograde way through palmar arch.
Surgical exploration demonstrated pronator teres syndrome. An anomalous fibrous band arising from the pronator teres muscle compressed the radial artery.
After resection of this fibrous band, the access was normally patent, even in supination. The patient did not experience any new episode of thrombosis at 1 year.
Discussion
Arterial upper-limb compression at the thoracic level is a usual problem. Entrapment at other locations below or just above the elbow is uncommon. Nearly all of the previously described patients with entrapment syndrome at this level presented with neurologic symptoms.1, 10, 11 We have described two cases of forearm arterial entrapment syndrome in patients having angioaccesses for hemodialysis. One was due to a fibrosis arcade arising from the flexor digitorum superficialis muscle; the other was due to pronator teres muscle syndrome (Fig 6, A and B ).
Fig. 6.
A, Forearm cross section's drawing figuring the sublimis bridge. During supination, the ulnar artery is compressed between both superficialis and profundus flexor digitorum. B, Anterior view of forearm, showing fibrosis arcade compressing the radial artery in pronator teres syndrome.
Several causes of forearm entrapment syndrome are described in the literature. The ligament of Struthers,5 described in 1849, is a clinically significant entity running from the supracondylar process or spur of the humerus to the medial epicondyle. This anatomical variation is known to occur in 0.7% to 2.7% of the population and has variously been called “supracondylar,” “supracondyloid,” “supraepitrochlear,” or “epicondylic.” This variation is usually asymptomatic. Occasionally, the pronator teres muscle may have an anomalous origin at the bone spur, the ligament, or both. The median nerve and the brachial, radial, or ulnar artery travel underneath the process or the ligament and may be compressed by either of them. Patients usually present with features of total or partial median nerve palsy with or without ischemia of the forearm.12, 13, 14 Weakness of the muscles supplied by the median nerve in the forearm, paresthesia over the thenar muscles, and claudication of the forearm after vigorous use are the most commonly observed signs.2, 6
Pronator teres syndrome was first described in 1951 by Seyffarth.15, 16 It is generally considered a rare condition. It is a neuropathy of the median nerve classically caused by entrapment of the nerve as it passes between the two heads of the pronator teres muscle. The resulting clinical picture includes some or all of the following features: paresthesia in the median distribution in the hand, weakness of the median innervated muscles distal to the site of entrapment, pain in the proximal forearm, and tenderness over the pronator teres muscle. Compression of adjacent vascular structures, which induces forearm claudication, has been reported infrequently.3, 4
Other causes of entrapment are also infrequently described, such as the one in our second case, involving compression by the fascia of the flexor digitorum superficialis muscle (sublimis bridge).10 This anatomical variation has been found in 8% of the population.17 It represents a remnant of the connections between the flexor digitorum superficialis (sublimis) and the flexor digitorum profundus muscles. Other anatomical variations involving the flexor digitorum superficialis muscle have been described by the same author: a slip connecting with the flexor pollicis longus muscle and another one connecting with the pronator teres muscle. Another above-the-elbow compression syndrome is related to an accessory bicipital aponeurosis.18
The clinical features of entrapment syndromes have been thoroughly discussed in the literature only at the thoracic level.19 In thoracic outlet syndromes, as in forearm entrapment, the clinical presentation is usually neurologic. Prevalence of vascular compression has been reported to be as low as 1%. At the level of the elbow, arterial involvement has been exceptionally described.6, 7 In the cases we presented, no forearm claudication was observed and no neurologic symptoms occurred; thus, no electromyogram was performed.
Both entrapment syndromes were revealed by angioaccess iterative thromboses. Classical causes of angioaccess failures were discussed and excluded. The etiology of these dysfunctions was found out to be related to a positional mechanism. With the patient in the supinated position, the flow was markedly reduced in the artery and led to iterative thromboses. The results of magnetic resonance imaging examination and surgical exploration disclosed the underlying cause of the forearm arteries entrapment: anomalous anatomical structures and increased diameter of the feeding artery.20, 21
In our opinion the frequency of arterial entrapment of the forearm artery is underestimated because it is asymptomatic in most patients. Entrapment involves only one of the forearm arteries and cannot cause ischemia because of the patency of the palmar arches. In our two patients, one of the forearm arteries was completely occluded, and the other was the site of positional entrapment. These vascular lesions did not cause any ischemic symptoms despite the steal by the angioaccess. In our first patient the radial artery was occluded, and in the supinated position the ulnar artery was also occluded. The patient did not have any ischemic symptom. In the supinated position the palmar arch was not fed, and the lack of ischemic symptoms was certainly due to the fact that the upper limb was in the supinated position for a short period of time. However, in those patients, arterial entrapment caused a major drop of the flow in the access that could not be compensated by the palmar arches, with the ulnar or radial artery being occluded. We think that the transitory drop in flow was the cause of otherwise unexplained iterative angioaccess thromboses of our two patients.
In one patient resection of the sublimis bridge restored normal clinical and radiologic patency of the normal radial artery whatever the forearm position. No thrombosis occurred during follow-up.
In cases of unexplained iterative forearm angioaccess thrombosis, involvement of an arterial entrapment syndrome must be ruled out. Responsibility of these anomalous anatomical structures in angioaccess thrombosis may be underestimated.
The evaluation of patients presenting with recurrent angioaccess failure, with no cause identified, should include a dynamic clinical examination. In case of doubt, an arteriogram will confirm the diagnosis of entrapment.
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☆ Competition of interest: nil.
☆☆ Reprint requests: Eric Chemla, département de chirurgie cardiovasculaire, hôpital Européen Georges Pompidou, 20, rue Leblanc 75015 Paris, France.
PII: S0741-5214(01)62226-2
doi:10.1067/mva.2001.116973
© 2001 Society for Vascular Surgery and The American Association for Vascular Surgery. Published by Elsevier Inc. All rights reserved.
