INCIDENCE AND MECHANISM OF INJURY

Lower extremity vascular injuries occur most frequently in young men. In both the urban and rural setting, penetrating injuries to the extremity are the most common cause of peripheral vascular trauma. Penetrating injuries occur more commonly in the urban setting because of high levels of interpersonal violence and mostly result from gunshot wounds or stab wounds.¹ Blunt injuries occur more commonly in the rural setting because of a higher incidence of farming and industrial-type injuries. In part caused by a rise in urban violence and high-speed motor vehicles, the incidence of peripheral vascular trauma is increasing. Compared with other arterial injury, such as in the neck and chest, which may be rapidly fatal, most isolated peripheral vascular injuries are not immediately fatal and patients usually survive transportation to a medical center.² Extremity vascular injury accounts for up to 50% of all arterial injuries seen at civilian trauma centers. Although the exact incidence of peripheral vascular injuries is variable, upper and lower extremity vascular trauma has a similar incidence in an urban setting. Within the lower extremity, femoral arterial injuries are more common than popliteal injuries and account for up to 70% of all lower vascular injuries treated in urban trauma centers.^4–15

DIAGNOSIS

The diagnosis of peripheral vascular trauma can usually be made based on a quick history and physical examination of the extremity, including a systematic and thorough neurovascular evaluation (Figure 1). There are a multitude of signs of vascular injury on examination. They are divided into hard and soft signs and reflect the likelihood that a significant vascular injury is present. Hard signs (Table 1) indicate a high likelihood that a significant vascular injury is present. Thus, patients with hard signs should be taken directly to the operating room to undergo immediate operative management.² Patients with soft signs of vascular injury (see Table 1) are less likely to have a significant vascular injury. This, however, must be confirmed using more invasive diagnostic modalities. Arteriography is currently the best available modality for the diagnosis of vascular injury in stable patients with soft signs of vascular injury but without evidence of peripheral ischemia. It can also be used in selected cases where the exact location of the injury is difficult to determine (e.g., pellet wounds or multiple gunshot wounds) and where the optimal incision and approach cannot be determined a priori. Arteriography can be performed in the angiography suite by an interventional radiologist or intraoperatively by the surgeon. It can be time consuming, but it is both sensitive and specific in the diagnosis of extremity vascular injury. Spiral computed tomographic angiography (CT-A) with the newest generation of high-speed scanner is an alternative diagnostic modality that has not yet been fully evaluated or widely accepted. It is rapid and does not require arterial catheterization. It does require contrast infusion, has no therapeutic potential, and can be limited by the artifacts generated if foreign bodies are present in the extremity.²

Figure 1 Algorithm for diagnosis of vascular injury in the lower extremity.

Table 1 Signs of Vascular Injuries

The types of arterial trauma that have been described include laceration, transaction (complete or partial), contusion (with or without thrombosis), aneurysm (true or false), arteriovenous (AV) fistula, intimal disruption, and external compression by a hematoma. Lacerations and transections account for the great majority of arterial trauma.¹

OPERATIVE MANAGEMENT FOR ALL PERIPHERAL VASCULAR INJURY

Intraoperative Management

Controlling active bleeding before the start of the operation allows for sufficient time to obtain proximal and distal vascular control without further blood loss and prevents contamination of the surgical field by further bleeding. Approaching the hematoma directly may be useful in selected cases, but good judgment is required, as this can result in significant and potentially needless blood loss, which can further compromise the patient’s hemodynamic and metabolic status, leading to a poor outcome. The cornerstone principle is to obtain proximal and distal control rapidly along with revascularization of the injured extremity. Surgical repair and temporary shunting are the main two options. The use of intraluminal shunt is advisable in patients who cannot tolerate surgical repair because of extreme systemic abnormalities such as acidosis, hypothermia, and coagulopathy. Also, when fracture stabilization may compromise the vascular repair, shunting should be performed before definitive vascular repair (Figure 2).

Figure 2 Algorithm for intra-operative management of vascular injury.

Surgical repair of arterial injury depends on the extent of vascular injury. Lateral arteriorrhaphy is recommended for management of small arterial lacerations that do not require debridement. Somewhat more extensive injuries requiring some debridement of the artery but without significant loss of the original length of the artery can be repaired via tension-free end-to-end anastomosis. Finally, for the most extensive injuries where free end-to-end anastomosis is not possible, the segmental defect can be bridged by autologous vein grafts (greater saphenous vein for lower extremity, cephalic vein for upper extremity) or synthetic conduits (PTFE, Dacron). Long-term patency rate and risk of infection should be taken into consideration when selecting between these two options. After surgical repair, adequate hemostasis must be insured, as well as distal limb perfusion. This can be evaluated using a continuous-wave Doppler device in the distal part of the affected extremity. If it is deemed unsatisfactory, a completion angiogram should be performed on the operating room table to look for technical problems with surgical repair, and the presence of common distal injury abnormalities such as thromboembolic complications or spasm or other traumatic injuries. When distal limb perfusion is deemed satisfactory, the wound should be assessed for adequate hemostasis, irrigated well, and debrided of necrotic and nonviable tissue before definitive wound closure. Complex wounds that involve large soft tissue defect may require live tissue flaps at a later time, which is beyond the scope of this chapter. Finally, patients with compartment syndrome or at a high risk for it, such as those with a combined arterial and venous injury, should undergo a therapeutic or prophylactic lower extremity fasciotomy.

MORBIDITY AND COMPLICATIONS

The most dangerous complications in the postoperative period are bleeding and thrombosis. Bleeding from the vascular repair may result in rapid swelling of the leg or external bleeding. This can be a life-threatening complication and mandates immediate return to the operating room for re-exploration and control of bleeding. At the same time, any coagulopathy should be corrected promptly. Arterial thrombosis at the site of the repair is suspected when the pulses are diminished or lost in the injured leg. Immediate return to the operating room to evaluate the vascular repair and to perform thrombectomy is essential to salvage the limb. The development of edema in the injured limb can result from thrombosis of the venous repair. Other complications include wound infection and deep infection at the site of the vascular repair. Delayed complications include stenosis and late thrombosis, pseudoaneurysm, and AV fistula. The surgical management of these complications is beyond the scope of this chapter. Chronic venous insufficiency has been associated with fourcompartment fasciotomy.¹

OUTCOME

There are three main outcomes after peripheral vascular trauma of the lower extremity: mortality rate, amputation rate, and functional outcome. The mortality rate after peripheral vascular injury has reached the lowest levels ever reported (<5%). This is attributable to rapid transport to a trauma center, adequate and prompt resuscitation, rapid diagnosis and treatment, and the use of damage control under the appropriate settings. In addition, the amputation rate has also dramatically improved (<2%), because of the institution of maneuvers resulting in abbreviated warm ischemia time. These include rapid transport from the scene to the operating room, better resuscitation, using intraluminal shunts, early stabilization of fractures, and liberal use of fasciotomy. The reported amputation rate after lower extremity vascular injury is highly variable.1–3,^16–19 Amputation rates for femoral artery injuries range from 0%–5%, and are much lower than those reported for popliteal injuries, which range from 0%–42%. Furthermore, any associated vein injury requiring ligation worsens the overall outcome and increases the amputation rate in the injured limb. A recently published study on blunt vascular trauma to the extremity reported that blunt vascular injuries reported an 18% amputation rate, which is considered to be three times the rate resulting from penetrating injuries. Higher amputation rates have been attributed to a delay in diagnosis as well as the presence of more significant injuries that delay the management of the extremity injury. Finally, the long-term functional outcomes of limbs with vascular trauma remain under-reported because of poor follow-up in this patient population, warranting further investigation.¹ A recent study²⁰ dealing with lower extremity injury reported that in limbs at high risk for amputation, reconstruction versus amputation results in equivalent functional outcome at 2 years after injuries.

CONCLUSION

There has been a significant improvement in the management of lower extremity vascular injury, resulting in lower mortality and higher limb salvage rates. These improvements in management, including preoperative, intraoperative, and postoperative care, have been emphasized in this chapter. Trauma surgeons should be familiar with these advances so that they can improve on the current outcomes of lower extremity vascular injury.