Chapter 4 Operative Exposure of Vascular Injuries of the Lower Extremity: Beyond the Bifurcation

This chapter will discuss techniques for exposure of injuries to the vasculature of the lower extremity beyond the bifurcation of the femoral artery down the leg. Though the major emphasis is operative exposure, the topics of perioperative considerations, positioning, and management of specific injuries will also be briefly discussed.

Learning Objectives

By the end of the ASSET course, participants should be able to do the following:

1. Describe proper patient positioning for distal superficial femoral and popliteal artery exposure.
2. Demonstrate surgical exposure of the distal superficial femoral artery at the adductor hiatus.
3. Demonstrate surgical exposure of the popliteal artery above and below the knee using a medial approach.
4. Demonstrate surgical exposure of the trifurcation vessels below the knee.

Considerations

• Incisions should be generous enough to allow proximal and distal control of the injured vessel(s).
• Self-retaining retractors are helpful, especially when adjusted at each level of exposure.
• Dissection should progress directly down to the vessel surface, followed by circumferential dissection once the vessel is identified. This approach helps avoid injury to associated structures (smaller branch vessels) and allows safe dissection of the vessel from its natural bed.
• The posterior approach to the popliteal artery is described in elective vascular surgery but does not have a role in the acute management of traumatically injured patients.
• Injuries to the vessels around the knee have a high likelihood of developing compartment syndrome, and therefore a low threshold should be maintained to perform fasciotomy. If fasciotomy is to be performed, the incision placed below the knee to expose the popliteal should also be used for medial fasciotomy.

Prepping and Positioning

• Extensive skin preparation and sterile draping are needed to ensure adequate proximal and distal access to the injured vessel(s).
• The groin, the abdomen up to the xiphoid, and both lower extremities (including the feet) should be prepped and draped.
• Do not tuck the arms. Both arms should be abducted to allow more room for the operating surgeon and to provide vessel access for anesthesia. Ensure that the table and positioning will allow for fluoroscopy without breaking the sterile field.
• Place the patient in a supine, anatomic position with full access to both lower extremities. There is no role for prone positioning in the acute care of a trauma patient with popliteal injury.
• Hip abduction and slight lateral rotation improve access to the saphenous vein and the popliteal vessels when using the medial approach.
• Placing a bump, usually a stack of several sterile towels, under the knee helps maintain appropriate positioning (Figure 1).

Exposure of the Distal Superficial Femoral Artery (SFA)

• The SFA is a continuation of the common femoral artery that descends into the subsartorial canal on the anteromedial aspect of the thigh and then into the popliteal canal.
• Proximal control of the SFA and the common iliac artery may be necessary and is described in chapter 3.
• Full exposure of the SFA is most easily achieved through an incision that parallels the inferior border of the sartorius muscle (Figure 2).
• The blood supply to the sartorius muscle (found on the muscle’s inferior medial border) should be preserved if possible, as this is the vascularized tissue of choice for coverage of SFA repair when there has been significant tissue loss (Figure 3).
• The adductor hiatus (Hunter’s or popliteal canal) is a fascial cleft located medial to the vastus muscles and lateral to the adductor muscles in the mid-thigh.
• The sartorius is retracted medially to expose the roof of the adductor (Hunter’s) canal; this allows subsequent unroofing of the canal and exposure of the superficial femoral vessels (Figure 4).
• The saphenous nerve should be identified and protected during dissection.
• After exiting the adductor hiatus, the SFA becomes the suprageniculate popliteal artery.

Potential Pitfalls

• Injury to the SFA may result in significant bleeding or hematoma that precludes a standard groin incision and dissection.
• In such circumstances, it may be necessary to gain control more proximally, as described in the previous chapter.
• Once bleeding is controlled (by direct pressure or pneumatic tourniquet, if available), proximal dissection and control is performed, followed by distal dissection and control.
• Venous injury often accompanies arterial injury. After arterial control is gained, the venous injury will need to be addressed before formal repair of the artery.
• If there is an injury to the deep vein(s), then ligation, shunting, or repair—depending on the injury and patient’s physiologic status—should be performed prior to restoration of arterial flow, as significant bleeding may ensue.

Popliteal Artery Exposure

Anatomy

• The popliteal artery is a direct continuation of the SFA, coursing posteriorly behind the knee and splitting into the anterior tibial artery and tibioperoneal trunk (TPT).
• The SFA becomes the popliteal artery once it exits the adductor (Hunter’s) canal and runs in close proximity to the joint capsule of the knee as it spans the intercondylar fossa.
• The popliteal artery gives off five genicular branches that supply the knee joint capsule and ligaments.
• Below the knee, the popliteal artery is sandwiched between the gastrocnemius and popliteus muscles, with the anterior tibial artery branching off at the lower border of the popliteus muscle.
• From a medial perspective, the semitendinosus (and its confluence with the gracilis and sartorius muscles to form the pes anserinus) and semimembranosus muscles cover the popliteal fossa and popliteal vessels.
• A small fat pad lies between the knee joint and the popliteal vessel sheath. Dissection of this fat pad aids in the identification, mobilization, and control of the vessels.
• The suprageniculate popliteal artery and vein are enclosed in a common sheath, with the artery found anterior in more than 90 percent of individuals.
• The popliteal veins are adherent to the popliteal artery with very little space between them, which can make the dissection tedious.

Exposure of the Popliteal Artery above the Knee

• With the leg positioned as in Figure 1, a generous skin incision is made on the medial aspect of the lower thigh in the palpable groove between the vastus medialis and sartorius muscles.
• The incision is carried down through the skin and subcutaneous tissues, keeping the saphenous vein in the posterior flap.
• Injury to the saphenous vein should be avoided if possible, as it is an important outflow vessel for the lower extremity.
• The vastus medialis and sartorius are identified with the popliteal fat pad containing the vascular sheath found between the muscle bellies (Figure 5).
• The distal adductor canal is opened by dividing the intermuscular fascia between the vastus medialis and the sartorius. Occasionally, the tendon of the adductor magnus muscle must also be divided.
• The popliteal artery is usually deeper than expected, being well-protected behind the femur.
• One way to quickly find the vascular sheath is to bluntly insert a forefinger into the popliteal fossa fat pad just above the sartorius muscle and push the finger across the thigh. The finger is then flexed such that the tip touches the underside of the femur. In this manner, the popliteal vascular sheath can be “hooked” with the finger and gently elevated into the wound (Figure 6).
• When opening the vascular sheath above the knee, the first structure that will be encountered is the popliteal artery, as it is found medial to the vein (Figure 7).
• The popliteal vein is carefully dissected free from the artery, taking care to preserve the small network of veins surrounding the artery, as well as the genicular arteries, of which there are three in the popliteal fossa.

Exposure of the Popliteal Artery below the Knee

• Exposure of the popliteal artery below the knee is usually accomplished through a separate incision.
• The leg is positioned as in Figure 1. The incision that is classically described to expose the infrageniculate popliteal artery is made 1–2 cm distal to the medial femoral condyle and 1 cm (a thumb width) behind the tibia; it measures about 10 cm in length (Figure 8).
• In the setting of vascular injury to the popliteal artery, there is a high likelihood that either a therapeutic or prophylactic fasciotomy will be indicated. If fasciotomy is needed, the incision to expose the infrageniculate popliteal artery should be the same as used to perform a medial fasciotomy (as described in chapter 5).
• Full exposure of the popliteal vessels below the knee requires that the gastrocnemius muscle be retracted inferiorly, the popliteus muscle retracted anteriorly, and the soleus muscle taken down from the tibia (Figures 9–12 and 14).
• Frequently, the distal popliteal vein is represented by anterior and posterior tibial veins that have not yet joined to form a single popliteal vein. Regardless of whether the popliteal vein is single or multiple, the location of the largest vessel will be medial to the artery and will be the first structure encountered (Figures 10, 11, and 13).
• The vein(s) is/are carefully dissected away from the artery after further division of the origin of the soleus from the tibia to expose the anterior tibial artery and the TPT, which subsequently divides into the peroneal and posterior tibial arteries (Figure 12).
• The tibial nerve is located posterior-medial to the vessels and should be avoided throughout the dissection.
• To gain further access to the vessels, the incisions above and below the knee can be connected (Figure 15).
• Division of these medial tendons can be safely performed with little postoperative disability if re-approximation is accomplished at the end of the case.
• The pes anserinus, which is composed of the conjoined tendons of the sartorius, gracilis, and semitendinosus, is divided along with the tendon of the semimebranosus muscles (Figure 15) to fully expose the length of the popliteal vessels (Figure 16).

Arterial Trifurcation and Beyond

• The trifurcation is exposed as described above, by identifying the infrageniculate popliteal artery as it crosses over the popliteus muscle between the gastrocnemius and soleus muscles (Figures 10–12 and 14).
• The anterior tibial artery is the first branch and comes off just after the popliteal crosses the inferior border of the popliteus muscle (Figures 10–12 and 14). The anterior tibial courses laterally and lies anterior to the interosseous membrane.
• The TPT continues under the soleus muscle and branches into the peroneal (fibular) artery laterally and the posterior tibial artery medially (Figures 12, 14, and 17).
• In roughly 5 percent of the population, there is a true trifurcation, where all three leg vessels branch from the distal popliteal artery.
• Only one intact vessel to the foot is needed to ensure tissue viability. The posterior tibial, anterior tibial, and peroneal (fibular) arteries have extensive collateral connections.
• The mid-portion and distal anterior tibial artery can be exposed through an incision on the lateral aspect of the leg made one finger in front of the fibula, in the same manner (though shorter) than the incision used for fasciotomy of the lower extremity (see chapter 5).
• The anterior compartment is opened and the anterior tibial neurovascular bundle is exposed by developing a plane between the tibialis anterior and extensor digitorum longus muscles (Figure 18).

Pearls and Pitfalls of Popliteal Artery Exposure

• Avoid injury to the saphenous vein. It should remain in the posterior flap of your proximal skin incision.
• Though it is not absolutely necessary to repair muscles and tendons divided for exposure, re-approximation should be considered when the patient’s physiology permits.
• Nerve injury is more common below the knee than in the thigh. Try to avoid injury to tibial and common peroneal (fibular) nerves.
• Avoid division of collateral geniculate vessels.
• Keep the salvageability of the limb in mind when dealing with severe popliteal trauma.
• When only one or two of the trifurcation vessels are injured, ligation is a viable option. If the patient is stable or if all three vessels are injured, then exposure and repair should be considered.
• Angiographic embolization is an acceptable alternative to surgical control of hemorrhage, particularly in locations that are difficult to access or in patients who might benefit from a less invasive procedure.
• If repair is needed, it is best accomplished with the help of an experienced vascular or trauma surgeon.
• If experienced vascular help is not available or the patient’s physiology does not allow definitive repair, the popliteal vessels can be shunted to maintain limb viability until definitive repair can be accomplished.
• Preoperative or intraoperative angiography is helpful to delineate the distal vasculature and to determine if formal repair or ligation will be needed.
• A proximal pneumatic tourniquet is a useful adjunct to consider.
• The most straightforward solution, using the most accessible artery that provides the best soft tissue coverage, is the ideal.