Dorsalis pedis artery aneurysm

Abstract

Aneurysm of the pedal arteries is uncommon. Dorsalis pedis aneurysms are a clinically rare phenomenon. We present a case of traumatic fusiform aneurysm of the dorsalis pedis artery in an otherwise well 53-year-old Caucasian man. Initial history was suggestive of micro-embolic disease to the medial toes of the left foot and on examination pulses were palpable throughout the lower limbs with a strong, palpable dorasalis pedis pulse. Ankle brachial pressure indexes were normal but reduced toe pressures to the left toes. Colour flow duplex imaging revealed aneurysmal dilation, involving all layers of artery wall, with irregular intraluminal thrombus across a 16-mm segment. Subsequent CTA run-off revealed all vessels were patent in the left lower limb. Due to concerns over further embolisation, our patient underwent successful ligation of the his dorsalis pedis. He had an uneventful post-operative recovery.

Background

Although uncommon, significant morbidity has been reported related to aneurysm of the dorsalis pedis artery.¹

Case presentation

A 53-year-old Irish Caucasian man presented to the vascular clinic with a 3-month history of cool toes on his left foot. The patient described the cold sensation with pain which occurred while driving and on elevation of the foot. He was otherwise active and well, denying claudication, rest pain or ulceration.

Background history was negative for diabetes, hypertension or hypercholesterolaemia. The patient was a non-smoker and family history was negative. Prior surgical procedures include four spinal discectomies, acromio-clavicular ligament repair, arthroscopy and left inguinal hernia repair.

Of particular relevance, the patient recalls having dropped an oxygen diving cylinder on the dorsum of the same foot, some years previously.

On examination, there were strong pedal pulses. There was no significant dorsal mass or systolic bruit.

Investigations

Investigation revealed a right and left ankle brachial pressure index of 1.18 and 1.17, respectively. Photoplethysmogram digital waveforms were measured but were absent on the left first, second or fifth toes with reduced amplitude of the third and fourth digits.

Colour flow duplex (Siemens Acuson s1000 Helx Evolution) showed a focal dilatation of the dorsalis pedis artery which extended for 16 mm from a point just inferior to the crossing of the ankle joint (figure 1). The vessel diameter ranged from 2.9 to 4.9 mm. Irregular intraluminal thrombus was visible, producing a viable lumen diameter of 1.3 mm (figure 2).

Figure 1.

Colour flow duplex showing focal dilatation of the dorsalis pedis artery.

Figure 2.

Irregular intraluminal thrombus was visible, producing a viable lumen diameter of 1.3 mm.

CT angiography (Siemens Somatron 64) confirmed the diagnosis and excluded further arterial abnormalities, showing non-aneurysmal aortic, iliac, femoral and popliteal vasculature.

Differential diagnosis

Initial history was suggestive of peripheral vascular disease with microembolic disease to the medial toes of the left foot but on examination pulses were palpable throughout the lower limbs with sinus rhythm, a normal echo and no aneurysmal disease above the knee.

A strong dorsalis pedis pulse was appreciated in the left foot which may have reflected intraluminal narrowing within the aneurysm sac, but there was no classical pulsatile mass on the dorsum of the foot.

Treatment

The patient underwent exploration and ligation of the left dorsalis pedis aneurysm. Findings were consistent with pre-op duplex images with focal arterial dilatation consistent with true aneurysm of the dorsalis pedis aneurysm, most likely traumatic in origin (figure 3).

Figure 3.

Intra-operative findings.

Outcome and follow-up

Our patient underwent successful ligation of his dorsalis pedis. He had an uneventful postoperative recovery and on review was well and symptom free.

Discussion

Infrapopliteal aneurysms are a rare clinical entity, first documented by Cuff et al in 1907.² Pedal aneurysms usually present as a slowly enlarging painless and pulsatile mass on the dorsum of the foot; with or without evidence of distal microemboli. While only a few cases have been described, significant pathology has been documented and forefoot ischaemia is a notable threat.¹

Trauma is the most common cause of aneurysm in this site however, it should be noted that patients may not recall the acute event as symptoms may only present once the patient experiences compression of local structures or embolic/rupture events.³ In comparison to an acute traumatic event, there are cases highlighting the role of repetitive low impact trauma causing atherosclerotic change and aneurysmal degeneration in patients otherwise not predisposed to atherosclerosis—examples include tight fitting shoes in patients with congenitally high arches as reported by Sonntag et al. ⁴

Alternate aetiologies of aneurysm formation include connective tissue disorders, primary atherosclerosis and mycotic aneurysm formation.^{5 6} Orthopaedic literature documents the uncommonly encountered phenomenon in the practice of foot and ankle surgery secondary, either to the initial fracture fragments, or to iatrogenic arterial wall injury during dissection, bony manipulation or fixation, causing pseudoaneurysm.^{7 8}

Aragao et al published a review of the literature in 2017 highlighting 24 reported true aneurysms of the dorsalis pedis.⁹ 67% were male, with 58% providing history of atherosclerotic risk factors. Most cases present with the classic dorsal foot mass, however one case is described as presenting with blue toe syndrome.¹⁰

Colour Doppler ultrasound and angiography are the diagnostic tools of choice.^{11 12} Aneurysms are considered significant when reaching more than 1.5 times their expected size. A case of true dorsalis pedis aneurysm extending to 8×5.3×4.1 cm³ highlights the potential for aneurysmal dilatation, intraluminal thrombus formation, rupture and distal ischaemia.¹³

Gold standard investigation for the patency of the pedal arch is operative angiogram, however, in patients where renal function is a concern VS magnetisation-prepared nMRA has been described as a non-invasive, radiation and contrast free alternative to CT/operative angiogram. It provides an excellent preview of the anatomy pre-operatively without compromising renal function.¹⁴

Surgical intervention is recommended given the risk of complications including: aneurysm rupture; emboli from intraluminal material and neurologic complications secondary to compression such as seen in our patient on planterflexion of the foot during driving.⁶ Management options include vessel ligation, patch angioplasty or reconstructive interposition grafting. Where there is adequate collateral circulation via patent posterior tibial and planter arteries, ligation of the affected dorsalis pedis vessel is a safe option.

In patients with diseased pedal arches or in those patients with risk factors for peripheral vascular disease, reconstructive options should be considered.⁶ Saphenous vein graft is documented.

Non-operative management is not recommended as acute rupture or ischaemic events may not be precipitated by symptoms. Review by Kato et al reported that 4% of infra-popliteal true aneurysms rupture and 12.5% undergo thrombosis.¹⁵

Learning points.

• Dorsalis pedis artery aneurysms are rare.

• They usually present as a pulsatile, soft tissue mass but can produce microembolic syndrome.

• They can be associated with significant morbidity.

• Diagnosis with colour flow Doppler ultrasound is rapidly accessible and highly sensitive.^{11 15}

• Management options include ligation/resection and reconstruction.