Minimally displaced fractures of the neck of the humerus are rarely associated with injury to the axillary artery [1]. In this context, the innocuous appearance of the x-rays can mislead the treating doctor into a state of complacency unless a thorough clinical examination is carried out in the Emergency Department. A missed arterial injury in these fractures, though infrequent, could potentially lead to disastrous consequences.

A relevant case is discussed and mechanisms related to vascular injuries in association with proximal humerus fractures are described with the emphasis on having a low threshold of suspecting and immediately treating such injuries in order to prevent catastrophic results.

The patient was admitted for monitoring of the distal pulses, but no further loss of pulsations was documented. At 12 months of follow-up, she had good functional outcome with a normally perfused limb.

Fractures of the proximal humerus account for 4-5% of all fractures [2]. Axillary artery injury in association with proximal humeral fractures remains low with respect to the close anteromedial relationship of the artery to the proximal humerus. The incidence of brachial plexus injury is relatively more common in these fractures [3]. Vascular injuries associated with proximal humerus fractures are more common in elderly patients [4]. The combination of osteoporosis and atherosclerosis may take part in the pathogenesis of this injury. Several authors have reported axillary artery injury following displaced fractures of the proximal humerus with or without subluxation [5, 6]. However, such injuries are rarely associated with minimally displaced proximal humerus fractures.

There are several mechanisms by which the axillary artery can be injured in proximal humeral fractures. A direct injury to the artery by a sharp bony fragment can cause laceration and rupture [1], violent overstretching can result in rupture especially in an atheromatous artery [6] and another important mechanism of injury is intimal tear and thrombosis. The artery stretches across the bony fragment, the adventitia remains intact and the fragile intima tears, leading to thrombosis. In our case, the angiography showed kinking and compression of the axillary artery at the fracture site which probably resolved spontaneously prior to intimal injury and thrombus formation. Axillary artery injury has also been described in a case of blunt injury to the shoulder without any fractures. Angiography in that case showed leaking of contrast material from a branch of the axillary artery. At formal exploration, a side branch of the axillary artery was found to be avulsed from the artery itself [7].

Diagnosis of axillary artery injury may be difficult as peripheral pulses may remain intact initially and later disappear. As a result, vascular injury can occasionally manifest several days after a fracture of the proximal humerus [8].

Paraesthesia is probably the most reliable symptom of inadequate distal circulation and should always be taken seriously. Collateral circulation around the shoulder is effective, and depending on the level of injury to the axillary artery, distal circulation might remain adequate and the patient asymptomatic [1]. In Drapanas's series, distal pulsations were present in 27% of the patients with major arterial injury [9]. Amputation rates following axillary artery ligation have been reported to be as high as 43% [10]. However, true arterial spasm occurs extremely rarely and is a presumptive, dangerous diagnosis to make [11].

Arterial injuries associated with proximal humeral fractures can be easily missed. Our case illustrates that minimally displaced fractures of the surgical neck of the humerus can be associated with vascular compromise and this can occur in the elderly with lesser degrees of force because of atherosclerotic rigidity of the artery. Potential complications can be avoided by careful examination of the patient and avoiding treatment of the x-ray alone.

Once a vascular injury is suspected, Doppler examination is necessary to establish the magnitude and quality of the arterial signal. Angiography should be performed immediately if arterial compromise is suspected after Doppler examination, and vascular surgeons should be consulted early in the management of such patients.

Written informed consent was obtained from the patient for publication of this case report and accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal.