Isolated Ulnar Artery Injury: Indications for and Timing of Operative Intervention

Upper extremity peripheral artery aneurysms are rare, accounting for only 0.5% of all peripheral artery aneurysms.^1,2 Pseudoaneurysms are defined by extravasation of blood into a false lumen confined by the tunica adventitia or perivascular tissue, in distinction to a true aneurysm, which involves all three layers of the arterial wall.¹ The ulnar artery is a rare location for both true and false aneurysms, with hypothenar hammer syndrome accounting for most reported cases.³ Here, we present a case of a distal forearm ulnar artery pseudoaneurysm occurring in an iatrogenic manner that was managed on an elective basis.

A 68-year-old male underwent removal of a superficial lipoma of the left volar forearm and wrist by the dermatology service. Difficult-to-control bleeding was noted upon removal of the lesions in the ulnar and volar aspect of the distal forearm. Direct compression was placed, and the patient was admitted to the emergency room for further evaluation and treatment.

Upon evaluation in the emergency room, no bleeding was noted from the wound. The patient was neurovascularly intact. An ulnar pulse was noted distal to the site of the injury. A radial pulse was also palpable, and the hand was warm and well-perfused. The patient denied pain, numbness, or tingling of the hand, and two-point discrimination of the fifth digit was found to be within normal limits (~5mm). The conclusion was that a branch of the ulnar artery was lacerated. The wound was closed primarily, and the patient was educated on recognizing the signs of potential complications. The patient was evaluated in the clinic 4 days later with a normal exam. One week later, the patient was again seen in follow-up; this time, a localized pulsatile swelling was noted at the site of injury. The exam was otherwise unchanged. A Doppler ultrasound revealed a pseudoaneurysm measuring nearly 8 mm with characteristic yin-yang sign (Figure 1).

The patient underwent exploration of the wrist that revealed a near-complete transection of the ulnar artery at the wrist with an accompanying pseudoaneurysm measuring 25 mm in length (Figure 2). This was excised, and an end-to-end anastomosis of the ulnar artery with 9-0 Nylon suture was performed under magnification. The patient’s postoperative course was unremarkable. A follow-up ultrasound performed 3 weeks after surgery showed a patent anastomosis without evidence of a recurrent pseudoaneurysm (Figure 3).

The ulnar artery is an important source of blood flow to the upper extremity and is usually the dominant arterial supply of the hand. It arises from the brachial artery at the level of the cubital fossa and courses deep to the brachialis muscle, pronator teres, and flexor carpi radialis. After giving off the common interosseous artery in the proximal forearm, it continues distally in the plane between the flexor digitorum superficialis (FDS) and flexor digitorum profundus (FDP). Along this course, it gives off small cutaneous perforators that are the basis of the ulnar artery flap.¹ Under normal circumstances, the ulnar artery is relatively well protected in the proximal and mid-forearm. In about 1-3% of cases, however, the ulnar artery takes a superficial course in the forearm.^5,6 At the distal forearm and wrist, the ulnar artery becomes a superficial structure and is covered by skin and fascia only, with the flexor carpi ulnaris tendon lying ulnar to the artery and the tendons of the FDS lying radially. It continues to the hand deep to Guyon’s canal, where it gives off the deep palmar branch that anastomoses with radial artery to form the deep palmar arch. The ulnar artery proper continues to form the superficial palmar arch in the hand. While the arborization patterns of the ulnar artery in the hand are known to vary,⁷ the bifurcation of the ulnar artery into the deep and superficial palmar arches is nearly always distal to the pisiform. Proximal to the pisiform in the distal forearm, the ulnar artery does not have any major branches that are the cause of significant bleeding; the ulnar palmar carpal branch, which anastomoses with the radial palmar carpal branch to comprise the palmar carpal arch, runs deep to the tendons of the FDP. Pulsatile bleeding at the wrist from a penetrating injury is therefore highly likely to represent injury to the ulnar artery proper.

Because of its intimate association with the tendons and nerves of the wrist—namely the flexor carpi ulnaris, FDS, and ulnar nerve—isolated injury to the ulnar artery is uncommon. As with any vascular injury, hard and soft signs must be assessed as part of a thorough history and physical. Hard signs include pulsatile bleeding, presence of bruit or thrill, signs of limb ischemia, and diminished or absent pulses. “Soft” signs include a stable, non-pulsatile hematoma, proximity of the wound to a major vascular structure, and hypotension.⁸ These findings must also be taken in context of the location of the injury as vascular injuries in the wrist and forearm are considered lower risk and less likely to result in a vascular compromise of the extremity. Some controversy exists on how low-risk injuries without hard and soft signs should be managed. While immediate surgical exploration is the established approach for obtaining hemostasis, there is a wide body of literature to argue that, in the absence of ischemia, the mere presence of a forearm arterial injury does not merit emergent or urgent repair if hemostasis can be achieved nonoperatively.⁹

Furthermore, whereas the concern for thrombosis, embolization, or rupture with hemorrhage and other complications of delayed diagnosis exists, this must also be put into the appropriate clinical context. The majority (90%) of patients with nonocclusive, clinically occult injuries do not report symptoms of arterial injury or require intervention.¹⁰ Even in cases where imaging does show evidence of an arterial injury, nonocclusive low-risk injuries rarely cause ischemic or hemorrhagic complications.¹¹ It appears that these patients can be safely managed with close follow-up if a nonoperative approach is undertaken.

As was the case in our patient, close follow-up can uncover a complication of arterial injury. Posttraumatic pseudoaneurysms can present days to years after the original insult^12-18 and can occur as a result of both blunt and penetrating trauma. Multiple case reports describe penetrating injury to the hand resulting in palmar arch pseudoaneurysms presenting in a delayed fashion.¹⁹ Although the majority of these are distal to the wrist crease, some studies report cases of injuries proximal to the wrist crease leading to ulnar artery pseudoaneurysms.²⁰ A review of 25 hand pseudoaneurysms over 18 years revealed that 76% were ulnar as opposed to radial, with 95% of those in Guyon's canal.

Pseudoaneurysms can present in various ways: as a mass, painful pulsating lesion, nerve compression, bleeding, or limb ischemia.^21-25 A thorough history and physical is imperative for diagnosis and management. Furthermore, use of an Allen's test evaluates the patency of the palmar arches. In addition, one should evaluate for pallor, decreased capillary refill, or petechiae,²⁵ as these findings can be indicative of a thrombotic or embolic insult. Doppler ultrasound evaluation and angiography are useful adjuncts in diagnosis.²³ The characteristic finding of a pseudoaneurysm on ultrasound is a yin-yang sign, which is a result of bidirectional flow of blood within the pseudoaneurysm. The neck of the pseudoaneurysm may be evaluated as well to help guide treatment.

Treatment of upper extremity pseudoaneurysms depend on the presence of vascular compromise. Distal ischemia mandates operative intervention. In the presence of an intact arch, proximal and distal ligation is a widely accepted treatment.¹⁹ A retrospective review of femoral artery pseudoaneurysms in 2002 demonstrated a 95% success rate in resolution of these with thrombin injections.²⁴ The first case report of ultrasound guided thrombin injection in an ulnar artery pseudoaneurysm was published in 2004.²⁶ This method is often highly successful but may need serial injections to completely occlude the false lumen.^27-29 The decision to proceed with open excision vs thrombin injection should be made on a case-by-case basis. Larger pseudoaneurysms and patients on anticoagulation are contraindications.³⁰

The vast majority of iatrogenic induced pseudoaneurysms of the upper extremity are due to cannulation of the arteries for percutaneous coronary artery evaluation. There is a trend for increased use of the radial and ulnar arteries for cardiac catheterization.³¹ While these techniques are less invasive, a review of 12 500 patients undergoing percutaneous catheterization showed a 0.05% rate of pseudoaneurysm formation, demonstrating a higher risk for this complication.³² With the increasing rates of cannulation of these vessels, it is important to be aware of the likelihood of increased incidence of these pseudoaneurysms.

This study reports an incident of iatrogenic injury to the ulnar artery proximal to the wrist, which later presented as a pseudoaneurysm. A delayed presentation is typical for this lesion. The outcome of this case supports the view that with close follow-up, nonoperative management of ulnar artery lacerations do not result in long-term adverse sequela, even if complications such as a pseudoaneurysm occur. When a suspected forearm arterial injury is managed conservatively, patient education and close follow-up are critical for addressing any delayed complications.

Affiliations: ¹School of Medicine, University of Louisville, Louisville, KY; ²Division of Plastic and Reconstructive Surgery, Department of Surgery, University of Louisville, Louisville, KY

Correspondence: Rachel H Safeek, MD, MPH; Rachel.safeek@gmail.com

Disclosures: The authors disclose no financial or other conflicts of interest.