Orthopedics

A False Aneurysm of the Ulnar Artery After a Forearm Compartment Syndrome

Kent Vincent, MD; William F Blair, MD

Abstract

ABSTRACT: A case is presented of a forearm compartment syndrome following a low velocity gunshot wound, with a subsequent ulnar artery false aneurysm. The diagnosis of a traumatic false aneurysm was delayed, presenting as a pulsatile mass with confirmation by arteriography. Early exploration and surgical treatment of the arterial system is recommended when a compartment syndrome follows a low velocity gunshot wound of the extremities.

Abstract

ABSTRACT: A case is presented of a forearm compartment syndrome following a low velocity gunshot wound, with a subsequent ulnar artery false aneurysm. The diagnosis of a traumatic false aneurysm was delayed, presenting as a pulsatile mass with confirmation by arteriography. Early exploration and surgical treatment of the arterial system is recommended when a compartment syndrome follows a low velocity gunshot wound of the extremities.

Introduction

False aneurysms of extremities are associated with penetrating injuries or fractures that perforate an arterial wall. An early compartment syndrome may also be a clue to underlying arterial pathology.1·2 The combination of a compartment syndrome and a false aneurysm after a low velocity gunshot wound is previously unreported. Our patient suffered a .22 caliber gunshot wound to the forearm, a compartment syndrome, and developed a false aneurysm of the ulnar artery. Surgical exploration of the involved arterial system is recommended when a low velocity gunshot wound results in an early compartment syndrome.

Case Report

A 40- year-old man presented eight hours after a .22 caliber bullet wound. The bullet entered the ulnar side of the left volar mid-forearm and exited via the left dorsal forearm. The volar compartment was palpably tense; passive extension of the wrist and fingers was painful. Two-point discrimination remained 5 mm in all digital tips. Distal ulnar and radial pulses were intact. Radiographs showed no fractures.

A debridement of the bullet tract and a fasciotomy of the volar forearm compartment was performed under axillary block. Four days later a partial closure of the fasciotomy was performed, followed by split-thickness skin grafting of the remaining open volar area. He was discharged nine days after the initial injury with a dynamic extension split. Moderate volar swelling persisted, but the neurologic exam was normal. Distal pulses remained palpably normal.

The patient slowly regained range of motion in the wrist and fingers over several weeks. He complained of occasional pain in the hand and forearm. As the diffuse forearm swelling gradually decreased, a persistent, firm. 6 cm by 2 cm pulsatile ulnar midforearm mass became apparent. A bruit was not auscultated over the mass, no thrill was palpable, and Doppler sonography revealed only a slightly diminished ulnar artery flow at the wrist. Seven weeks after the initial injury, an arteriogram showed an opaque false aneurysm of the left ulnar artery 4 era distal to its origin, measuring 3 cm in length by 1.7 cm in width. The ulnar artery was faintly opaque beyond the false aneurysm (Fig. I).

The false aneurysm was then resected after proximal and distal ligation of the artery. Postoperatively the patient did well with the exception of a mild flexion contracture involving the palmaris longus and the flexor superficialis muscle group.

Discussion

Traumatic aneurysms in the upper extremity are classified as either true or false aneurysms. The mechanism of injury in the rarer true aneurysm is a nonpenetrating Wow or repetitive trauma at the same site. Damage to collagen and elastin fibers in the arterial tunica media results in gradual dilatation of the artery over a period of days to months. The intima remains in continuity.

A false aneurysm develops after a penetrating injury that perforates the wall of an artery. These aneurysms occur after gunshot wounds,3-6 explosions,3,4 fractures,7 dislocations,8 various stab wounds,911 and as postoperative complications. Bleeding from the perforation into the surrounding tissue is contained by adjacent fascia and soft tissues. Pulsation indicates that the hematoma formed is still in communication with the arterial lumen and is thus enlarging. In most cases bleeding stops and the clot organizes. Minor trauma such as re-bandaging or probing the wound may result in renewal of bleeding with further enlargement of the hematoma. The balloon-like aneurysm may stabilize, but an enlargement and recanalization process may continue for weeks.

Symptoms of a false aneurysm may include pulsations, localized pain, and loss of distal motor or sensory function secondary to nerve compression. Examination most often reveals a localized, pulsatile mass. The presence of a palpable thrill suggests an arteriovenous fistula. Persistent swelling may be present, even long after a fasciotomy. Depending upon the size of the defect in the arterial wall and upon compression from the false aneurysm, distal pulses may be diminished. Definitive diagnosis depends upon arteriography, in which contrast material typically outlines the bulbous projection from the artery.

Fig. 1: An arteriogram demonstrates a false aneurysm of the ulnar artery.

Fig. 1: An arteriogram demonstrates a false aneurysm of the ulnar artery.

Upper extremity false aneurysms made up 27.4% of all false aneurysms reported in the Vietnam Vascular Registry.4 The brachial artery was the most common site in the body for false aneurysms (Table 1). Etiology of injury in this series most commonly involved fragments from exploding devices (87.3%) rather than actual bullet wounds (10.6%).

In the upper extremity, false aneurysms most commonly involve five sites.9,12 The brachial artery may be damaged with trauma in the axilla or in the antecubital fossa. In the hand the ulnar artery is commonly penetrated as it crosses lateral to the hook of the hamate, and where it runs most superficially in the hypothenar eminence. The radial artery may be damaged as it crosses anterior to die styloid process of the radius.

A key clinical feature of false aneurysms is their late presentation relative to the initial injury.4,'3,"4 In a series of 558 false aneurysms and arteriovenous fistulas from the Vietnam War, only 3.9% of the vascular injuries were diagnosed within 24 hours of injury, while 47.2% presented one month or more after the insult. A typical presentation is between diree and 12 weeks after the initial injury.

Table

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In general false aneurysms should be operated upon when first diagnosed. 3,4,'5-'7 Surgical technique and repair of the false aneurysm depends upon size and location of the lesion. If the aneurysm is located distally, and if collateral blood flow is adequate, excision of the sac wiüi ligation of the proximal and distal artery is the treatment of choice. If the false aneurysm involves the axillary, brachial, or proximal ulnar or radial artery, however, vascular reconstruction may be desirable. Excision of the aneurysm followed by end-to-end arterial anastomosis is preferred. If this is not technically possible, vein grafting may be indicated.

Most gunshot wounds seen in the civilian population involve low velocity missiles. 17 Low velocity gunshot wounds have been reported as the etiologic factor in 9% of compartment syndromes in Sheridan's series.18 However, the specific combination of a low velocity gunshot wound with a compartment syndrome and false aneurysm has not been described. Our experience with this patient's clinical presentation, which included an early compartment syndrome, relatively slow rehabilitation secondary to persistent complaints of forearm pain , and slowly resolving forearm swelling, was suggestive of false aneurysm. The diagnosis was indicated by the development of a pulsatile mass and confirmed by arteriography. On the basis of this experience, prompt exploration of the arterial system in the presence of a compartment syndrome complicating a low velocity gunshot wound of the extremities is recommended.

References

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13. Gelberman R. Garfin S. Hergenroeder P, et al: Compartment syndromes of the forearm: Diagnosis and treatment. Clin Orthop 1981: 161:252-261.

14. Sheridan G. Matsen F: Fasciotomy in the treatment of acute compartment syndrome. J Bone Joint Surg 1976; 58A:1 12-1 15.

15. Rich N. Hobson R. Collins G: Traumatic arteriovenous fistulas and false aneurysms: A review of 558 lesions. Surgery 1975: 78:817-828.

16. Wmegamer F. Baker A. Bascom J, et al: Delayed vascular complications in Vietnam casualties. J Trauma 1970; 10:867-873.

17. Green DP: True and false traumatic aneurysms in the hand. J Bone Joint Surg 1973; 55A:120-128.

18. Engelman R. Clements J. Herrmann J: Slab wounds and traumatic false aneurysms in the extremities. J Trauma 1969: 9:77-87.

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10.3928/0147-7447-19841201-10

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