Popliteal and Shank Arterial Injury

Vascular Trauma

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Popliteal and Shank Arterial Injury

William H. Snyder, III, M.D. *

Arterial injuries of the lower extremity below the adductor hiatus result in amputations more often than do injuries in any other site. This risk is well known for popliteal wounds and has recently become apparent for injuries of the infrapopliteal or shank arteries. The principal deterrents to limb salvage are delay in diagnosis and revascularization and extensive adjacent bone and soft-tissue trauma. Arterial wounds from low-velocity single missiles or sharp objects infrequently result in amputations, but more than 20 per cent of limbs are lost after blunt trauma and shotgun or high-velocity missile injuries. Rapid diagnosis and revascularization is required for all patients with popliteal artery injuries and for those with infrapopliteal injuries that compromise distal flow. The optimal management of isolated shank arterial injuries with normal 'w in uninjured parallel vessels is unclear.

INCIDENCE AND MECHANISMS OF INJURY Popliteal and shank arterial injuries each constitute about 20 per cent of battlefield arterial injuries and 5 to 10 per cent of civilian wounds. 7 • 10. 36. 40 One-third of major lower limb injuries harbor underlying vascular wounds, half of which involve vessels below the adductor hiatus. 27 Combined skeletal and vascular trauma is particularly common in this site; wounds of the popliteal or shank arteries accounted for three-quarters of the combined injuries in a recent series from Chicago. 1 Arterial wounds accompany skeletal injuries in 32 per cent of knee dislocations, 2 per cent of tibial-fibular fractures, and 0.5 per cent of femoral fractures. 13, 20 In urban America, vascular wounds of the leg most commonly result from penetrating trauma. Single low-velocity missiles and sharp instruments are the usual causes, and gunshot wounds predominate. However, depending on the population source, 25 to 60 per cent of popliteal and shank *Professor, Department of Surgery, University of Texas Southwestern Medical Center, Dallas, Texas

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arterial Injuries are from blunt trauma. 5, 6. 9, 15, 18, 21, 25, 26, 33, 48. 54 In rural populations, blunt injuries are more common and cause arterial wounds by compression forces, traction from fracture displacement, or direct trauma from bone fragments. Adjacent tissue damage commonly accompanies vascular injuries of the knee and leg, especially with blunt trauma and high-velocity bullet or shotgun wounds. FREQUENCY OF LIMB LOSS When treated by ligation in World War II, 73 per cent of popliteal arterial injuries resulted in amputations. 7 Despite improvements in vascular techniques and rapid battlefield evacuation, the amputation rate remained approximately 30 per cent in Vietnam. 39 Until recently, civilian popliteal trauma has also caused limb loss in more than 30 per cent of injuries. 5, 9 An amputation rate of 12.7 per cent in a civilian series of 110 popliteal artery injuries was reported in 1982. 48 The rate of limb loss was 9 per cent for penetrating trauma, including rates of 20 per cent for shotgun wounds, 4 per cent for single-missile injuries, and zero for stabwounds. Blunt trauma led to limb loss in 24 per cent (the highest injury-specific rate), which has been the usual experience. Recent reports document continually improving limb salvage in patients with these injuries. 53 Lim and coworkers treated 31 consecutive patients with popliteal artery injuries of various etiologies, and Shah and associates treated 30 consecutive blunt injuries, with no major amputations. 25, 46 These are remarkable results, and some of the concepts outlined below are borrowed from those authors' experience. The amputation rates after tibial artery ligations in World War II were 14 per cent after single-vessel injuries and 65 per cent after injuries of both anterior and posterior tibial arteries. 7 In Vietnam, amputations followed wounds of single tibial arteries in 20 per cent of patients having arterial repairs and 75 per cent of those having ligations. 38 Civilian trauma resulted in a cumulative amputation rate of 18 per cent in 99 patients in recent reports of infrapopliteal arterial injuries from assorted causes. 15, 18, 21. 22, 54 In a series of 51 patients with 82 arterial injuries, limb loss most often followed blunt trauma (23 per cent), shotgun wounds (33 per cent), and injuries of all three infrapopliteal vessels (60 per cent) or the tibioperoneal trunk (50 per cent).21 These high amputation rates usually reflect major associated musculoskeletal wounds. The serious threat to limb survival in patients with combined vascular and skeletal injuries of the knee and leg has been recently emphasized in reports describing amputations after one-half Qf such injuries. 12. 20, 23 Specific factors related to diminished limb survival are treatment delays of more than 6 hours, extensive musculoskeletal and skin damage, and a distal level of arterial injury. Crush trauma, such as is inflicted by pedestrian-automobile bumper injuries, and segmental or distal open tibial fractures are especially prone to limb loss. ANATOMY Knowledge of the anatomy of the popliteal and shank arteries is important for assessing the likelihood of underlying arterial wounds and for

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a----+-Femoral a.

~I----Popliteal

Figure 1. Anatomy: Popliteal and shank arteries.

a.

a-+--+--Tibioperoneal trunk a. U-I~-Anterior

tibial a.

Posterior tibial a. 1-1-'-\-4--

Pera neal a.

planning operative exposure (Fig. 1). The popliteal artery begins at the tendinous hiatus of the adductor magnus muscle, extends several centimeters below the knee joint, and gives ris~ to the anterior and posterior tibial and peroneal arteries. The artery is tethered to the distal femoral shaft at the adductor hiatus and to the proximal tibia by the tendinous arch of the soleus muscle. Distortion of skeletal anatomy, as occurs with knee dislocations or fractures of the distal femur or proximal tibia, may result in stretching or direct injury to the artery.19 The collateral network around the knee is abundant but frail, predisposing to ischemia after acute popliteal artery occlusion. These delicate vessels maintain some distal perfusion after traumatic arterial occlusion but are easily obliterated by swelling of the perigenicular soft tissue, resulting in distal small-vessel thrombosis. This may partially explain why fewer limbs are salvaged after diffuse injury than after sharp wounds. The termination of the popliteal artery is frequently referred to as a trifurcation, but this pattern is unusual. The artery most often bifurcates into the anterior tibial artery and the tibioperoneal trunk an average distance of 5.8 cm below the tibial plateau. 3O The anterior tibial artery crosses the interosseous septum and descends in the anterior fascial compartment. The tibioperoneal trunk divides into the posterior tibial and peroneal arteries

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an average distance of 3. 7 cm beyond the origin of the anterior tibial artery. These vessels descend in the deep posterior fascial compartment; the posterior tibial is medial and is directly behind the tibia in the proximal leg. The malleolar vessels form a rich collateral network around the ankle that often maintains distal pulses after occlusion of one major inflow artery. Injuries immediately below the knee or above the ankle are more likely to interrupt flow completely because only two vessels traverse these sites, compared with three vessels in the mid-leg. Blunt trauma or multiple missiles more often compromise flow than do sharp instruments or single missiles by injuring more than one vessel and as a result of compartmental hypertension. 21

EVALUATION AND TREATMENT GENERAL PRINCIPLES

Initial Management Distal ischemia is the predominant problem in the early management of injuries of the popliteal and shank arteries. Hemorrhage is seldom severe and usually can be controlled with external pressure. Tourniquets should be avoided, because they occlude collateral inflow and may lead to further circulatory compromise and greater ischemic damage. Vascular clamps should not be applied in the depths of the wound without adequate exposure; accurate clamping usually requires operating room facilities. Rapid diagnosis and revascularization is required for arterial injuries that may threaten limb survival, which includes all wounds of the popliteal artery or tibioperoneal trunk and those involving more than one shank artery. The optimal management of injuries of single infrapopliteal arteries is less definite. Clearly, operations are required for injuries causing acute symptoms or complications, but the need to treat occult wounds is speculative. The potential morbidity of asymptomatic single-artery wounds is the late development of false aneurysms or arteriovenous fistulas, and this possibility must be weighed against the task of excluding such injuries in all patients with shank trauma. 4, 41 The initial goals in patients with wounds that threaten limb survival are the accurate diagnosis or exclusion of arterial injury and the recognition of compartmental hypertension. Patients with ischemic limbs are given anticoagulation with heparin, if this is not contraindicated by other injuries, to minimize distal small-vessel thrombosis. 6 Revascularization and, if needed, fascial decompression are performed unless extravascular injuries preclude a functional extremity, in which case the patient is best served by primary amputation. The importance of rapid treatment of popliteal and shank arterial injuries with compromised flow has been documented repeatedly. 13, 20, 23, 26, 48, 53 The effect of the ischemic interval has been studied, although other variables preclude defining an absolute time limit beyond which limb salvage is impossible. Extremity salvage following revascularization of the

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Table 1. Signs of Arterial Injury Hard Ischemia/pulse deficit Bruit Expanding/pulsatile hematoma Arterial bleeding

Soft Stable/small hematoma Adjacent nerve injury Unexplained shock Proximity

animal equivalent of popliteal artery interruption was 90 per cent after 6 hours, 50 per cent after 12 to 18 hours, and 20 per cent after 24 hours. 29 These data are not directly applicable to human injuries but do emphasize the importance of avoiding delay in revascularization. In a collected review of 78 patients with arterial injuries associated with knee dislocations, the amputation rate was 13 per cent if arterial flow was restored within 8 hours and 86 per cent with longer delays. 13 Diagnosis and Indications for Operation The possibility of a penetrating arterial injury is announced by a wound in proximity to a major vessel and supported by the signs listed in Table 1. Diagnostic persistence is necessary to avoid overlooking blunt popliteal injuries as well as those involving the tibial and peroneal arteries from any cause. Impressive advances in diagnostic techniques have been made, but the history and physical examination remain the basis for diagnosing vascular injury, as discussed in the first article in this isssue. Diminished pulse volume is the most common finding that leads to the diagnosis. The important observation, documented by numerous reports, is that a palpable pulse does not ensure the absence of a proximal arterial injury. 36, 44, 47 Normal pulses are present in about 15 per cent of limbs with injuries of the popliteal or of more than one shank artery. 21,50 The first four signs listed in Table 1 are almost pathognomonic Chard") of an underlying arterial injury; the last four are less specific and are considered "soft" signs. 49 Patients with hard signs of arterial injuries that are adequately localized by physical examinations or plain radiographs are best served by early operations. Urgent operations are mandatory in patients with ischemia because delay may prevent a successful revascularization. A single-film arteriogram can be obtained rapidly in the emergency room or operating room if additional information is required. 32 Equivocal or soft signs suggest the presence of arterial injury, and arteriography or operative exploration may be necessary to exclude or confirm this possibility. Noninvasive examinations with the Doppler and pulse volume recorder are being used more frequently in the evaluation of patients with potential arterial injuries. 46 Although these methods are more sensitive than palpation of pulses, their accuracy is not sufficient to exclude an arterial injury. They do provide an effective means of monitoring patients with equivocal signs of injuries, especially those requiring orthopedic procedures or urgent operations for remote injuries (see first article in this issue). Arteriography is the single most useful diagnostic procedure for detecting an arterial injury. The validity of normal arteriography in excluding arterial injuries in patients with equivocal signs was substantiated in a prospective study reported in 1978. 49 Arteriography can be used to diagnose

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Table 2. Considerations for Primary Amputation Magnitude of extremity trauma Nerve: anesthetic/anatomic interruption Soft tissue: crush/degloving Bone: comminuted/bone loss (>6 cm) Severe remote trauma; hemodynamic instability Multidisciplinary involvement Final decision: anesthetized patient in operating room

the injury, to define the site precisely, and to examine the collateral flow and the patency of the distal arterial tree. It may be necessary to delay the operation to obtain high-quality studies, and this could be detrimental to some patients. Arteriography should be selected for patients in whom the findings may eliminate the need for an operation or simplify its performance. The need for venography in vascular trauma is less well defined. Venograms may assist intraoperative decision-making by demonstrating venous anatomy and occult pathology. For instance, paired popliteal veins suggest that the surgeon can safely ligate one of the pair, and the demonstration of a venous thrombus indicates the need for thrombectomy. 2 In patients with arterial injuries but without ischemia, venography is occasionally obtained in conjunction with the preoperative arteriogram. Considerations for Primary Amputation Immediate amputation of a severely traumatized limb is a difficult but critical decision that presents early in the care of patients with such injuries. This decision relates to the projected likelihood that a functional and durable extremity can result and does not apply to isolated vascular injuries. 53 The attitude that vascular reconstruction is always indicated is inappropriate and may result in serious morbidity. Major limb trauma has been characterized as "multisystem extremity injury" if the injury involves at least three of the four organ systems (integument, nerve, artery, and bone). Based on this concept, Gregory and associates devised a scoring system that may be helpful in identifYing unsalvagable extremities. 14 The decision for primary amputation requires a judgment of the magnitude of the trauma, the most important components of which are the nerve and musculoskeletal injuries (Table 2). An anesthetic and paralyzed extremity is usually best treated by immediate amputation. Operative confirmation of the basis of the neurologic deficit-destruction, contusion, or ischemia-is usually advisable. The loss of bone continuity of 6 cm or more also portends a poor functional result. The importance of soft-tissue injury is more relative, and in the absence of other unrepairable injuries, reconstruction is often possible. Extensive remote trauma that necessitates priority attention for the preservation of life is occasionally definitive. The vascular injury is essentially never a deciding factor. Multidisciplinary involvement in the decision is beneficial, and the final decision regarding primary amputation usually should be made in the ideal circumstances provided by an anesthetized patient in the operating room. According to Lange and associates, absolute indications for primary amputation in patients with vascular injuries and open tibial fractures are

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anatomically complete disruption of the posterior tibial nerve in adults and crush injuries with warm ischemia of more than 6 hours. 23 Relative indications include serious. associated poly trauma, severe ipsilateral foot wounds, and the anticipation of a protracted course for soft-tissue coverage and tibial reconstruction.

SPECIFIC INJURIES

Popliteal Artery Popliteal arterial injury can usually be diagnosed rapidly if the initial examiner appreciates the signs and implications of this injury. Seventy per cent of patients present with pulseless extremities, and many also have other signs of ischemia. 48 These findings usually lead to a rapid diagnosis and an immediate operation. Thirty per cent of patients present with less obvious signs, however, and half of these have only wounds that are proximate to the vessels. Most penetrating popliteal injuries can be identified by adhering to the principle of arteriographic or operative exclusion of suspected arterial trauma. The diagnosis of blunt injury often is less obvious, and this circumstance explains most treatment delays. For this reason, arteriography is recommended to exclude blunt arterial injury in patients with knee dislocation, knee instability after acute blunt trauma, displaced fractures near the knee with circulatory deficits that resolve after reduction, compression injuries from automobile bumpers, or fractures near the knee requiring operation, particularly if a tourniquet is to be used. Urgent operations without delay for arteriography are indicated in patients with popliteal injuries and signs of ischemia. Unless contraindications exist, these patients are immediately given heparin to limit distal small-vessel thrombosis. Arteriography is used selectively in patients with overt signs of injury but without ischemia, the selection being based on the urgency of revascularization and th~ localization of the arterial injury by the external wound. Tibial and Peroneal Arteries The management of wounds of the shank arteries is based on the presenting findings and the specific vessel(s) injured. The initial goals are the rapid revascularization of injuries causing ischemia and the detection of wounds that may threaten limb survival or cause delayed complications. Leg wounds are very common; careful selection is required to avoid the excessive use of diagnostic arteriography to achieve these goals. Operations are required for injuries that cause acute symptoms or complications (e. g., ischemia, hemorrhage, compartmental hypertension, arteriovenous fistulas, or false aneurysms) and for those that may threaten limb survival (e.g., tibioperoneal trunk or more than one distal artery). The potential morbidity of single asymptomatic injuries of the anterior or posterior tibial or peroneal arteries is the development of chronic false aneurysms or arteriovenous fistulas. Although these lesions account for approximately one-third of the delayed problems that necessitate operations

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after arterial injuries, their incidence after untreated occult wounds is not known. 4 • 41 Most subfascial leg wounds are proximate to at least one of the shank arteries, and routine arteriography would be required to exclude all injuries. Because of the size and flow rates of the distal shank arteries, false aneurysms and arteriovenous fistulas infrequently cause significant morbidity or dangerous problems with delayed operative repairs. This risk is probably not sufficiently great to justify arteriographic exclusion of all asymptomatic injuries of single shank arteries. The diagnosis of wounds of infrapopliteal arteries is based on the signs outlined in Table 1 and is supplemented by arteriography, depending on the clinical circumstances. The risk of limb loss is not commonly appreciated, even in patients without palpable pulses, as evidenced by an average preoperative delay of 5 hours in a recent civilian series. 21 Injuries causing distal ischemia require rapid operations, and, unless contraindicated, anticoagulation with heparin is instituted preoperatively to limit distal smallvessel thrombosis. Arteriographic demonstration of the site(s) of arterial injuries, if needed, is obtained by single-injection studies in the angiography suite, emergency room, or operating room. 32 Injuries of single shank arteries may not be apparent because distal pulses are often maintained by collateral flow around the ankle. Such injuries may sometimes be demonstrated by disappearance of the pulse with digital compression of the other ankle vessel. If no signs of arterial injury can be elicited, the problem becomes that of excluding injuries that will threaten limb survival if delayed occlusion occurs. For this purpose, diagnostic arteriography is recommended for penetrating wounds that traverse the central leg, particularly in the proximal or distal thirds, and for severely displaced or comminuted tibial fractures. 21 • 23 In patients with penetrating trauma, if there are no signs of arterial injury and the trajectory is unlikely to have entered the deep posterior compartment, the possibility of a limb-threatening injury is small. Although wounds resulting in false aneurysms and arteriovenous fistulas may be missed by this approach, serious morbidity is unlikely, and numerous invasive procedures are avoided. Reconstruction is mandatory for wounds of the tibioperoneal trunk or of more than one distal artery. Asymptomatic wounds of single vessels that are detected arteriographically are managed selectively. To minimize delayed complications, operations are recommended for major wounds of the vessel wall manifested by extravasation, occlusion, false aneurysms, or arteriovenous fistulas. Minor arteriographic defects such as wall irregularities or intimal flaps in nonessential vessels are less likely to develop complications and operations are often unnecessary.

SUMMARY OF INITIAL MANAGEMENT

The initial management of patients with major knee or leg trauma is most effectively based on the state of distal perfusion at the time of presentation (Table 3).

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Table 3. Initial Management of Knee/Leg Trauma Ischemic limb Systemic heparin-unless contraindicated Urgent operation ?Emergency room/intraoperative arteriography ?Initial fasciotomy Revascularization Nonischemic limb Arteriography of suspicious lesions Knee (proximity; unstable knee or "bumper injury") Leg ("core" penetration-proximal/distal third; segmental/ comminuted tibial fracture) Expeditious revascularization

OPERATIVE TREATMENT GENERAL PRINCIPLES

Exploration and Vascular Control General anesthesia is required for all but the most minor and distal injuries. The entire extremity is included in the sterile field; access to the groin may be necessary for arteriogram injections, and distal access allows palpation of pulses or Doppler examination and retrograde thrombectomy. The entire contralateral extremity is also prepared to harvest saphenous vein if this becomes necessary. Vertical incisions are made over the vessels to be explored to allow proximal and distal extensions. If possible, the vessel is initially exposed and controlled outside the hematoma, away from the suspected site of injury. In the event of hemorrhage during exposure, bleeding is controlled with digital pressure until vascular clamps can be applied. Following isolation of the injured arterial segment, the extent of damage is evaluated, and nearby veins, nerves, and other structures are examined. ., If collateral circulation is adequate, the vessel may safely be occluded during repair. Signs of distal ischemia preoperatively or impaired backHow mean that collateral How is inadequate and indicate the need for further measures. Intraluminal thrombus is often present, especially with wounds causing vessel occlusion; balloon catheter thrombectomies of injured arteries and veins may enhance collateral How during the dissection and reconstruction. The distal vessels are irrigated with copious amounts of cold balanced saline containing 10 units of heparin per ml of solution. In patients with distal ischemia and combined arterial and venous injuries, it may be helpful to Hush the distal arterial tree with a solution of 1000 units of heparin and 12.5 gm of mannitol in a liter of lactated Ringer's solution until the venous effiuent is clear.35 Heparin affords some protection to the occluded segment by retarding thrombosis, the irrigation removes thrombotic debris, and mannitol may decrease muscle edema and the need for subsequent fasciotomy. If a delay of more than an hour or two is anticipated before revascularization is completed, an indwelling shunt may be useful.

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Sequence of Repair The appropriate sequence for arterial and venous reconstruction and the repair of skeletal injuries has been widely debated. If distal flow is maintained, the sequence of repair is a matter of personal preference. Arterial injuries causing distal ischemia or venous injuries causing venous hypertension require immediate restoration of blood flow by definitive reconstruction or temporary indwelling shunts. Venous repair is usually performed first, thus providing better outflow, which may enhance the success of the arterial reconstruction. 40, 42 Controversy continues regarding the need to stabilize fractures before reconstructing vessels. Initial bone stabilization protects the vascular repair from damage by movement of the fracture site. The disadvantages of this sequence include delay in restoration of flow to ischemic tissue and possible interference with a technically competent vascular repair by the fixation device, which may impede access to the injury as well as obscure the arteriographic study of the completed reconstruction. Repair of vascular injuries first is recommended, especially in patients with ischemia. This approach requires that the vascular surgeon remain in attendance during the orthopedic manipulation to ensure that the vascular repair is not exposed to excessive movement. Managed in this way, orthopedic manipulations disturbed fewer than 10 per cent of vascular repairs in patients with popliteal artery injuries,50 With the vascular surgeon in attendance, such complications are readily detected and corrected, Occasionally, an extremity is so shortened or a fracture is so unstable that initial stabilization is necessary. Method of Repair Adequate debridement of injured vessels is as important as in other tissues. There is a natural reluctance to debride vessels widely, because this may preclude primary anastomosis, but failing to resect a transmural injury may result in the development of a false aneurysm. Moreover, damaged intima promotes platelet aggregation and so may increase the risk of occlusion. Debridement is particularly important in gunshot wounds and blunt trauma because there is often blast damage and contusion beyond the obvious injury. This usually requires resection of 4 to 5 mm of vessel beyond the overt injury in low-velocity missile wounds and of at least 1 cm in high-velocity missile wounds and blunt injuries. The type of vessel injury and the extent of debridement required will determine which method of repair is best. Lateral repair is occasionally possible for wounds from sharp instruments, but most injuries from today's severe violence require segmental arterial resections. After resection for low-velocity missile injury, an end-to-end vascular anastomosis is often feasible, but any difficulty in approximating the vessel ends indicates the need for an interposition graft. Adequate debridement of vessel injuries from blunt trauma or high-velocity missiles usually precludes primary anastomosis, and interposition grafts should be used liberally in the repair of these injuries. Bypass or interposition grafts were considered necessary in more than 75 per cent of reconstructions for popliteal or limb-threatening infrapopliteal

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arterial injuries in recent series. 12, 21, 25, 26, 34, 52 Interposition grafting is the usual method of reconstruction, but extra-anatomic bypass is sometimes advantageous. Following th€ lead from elective vascular techniques, in situ saphenous grafts and nonreversed venous autografts are occasionally used. 46 Remote bypass avoids dissection in the site of injury, and the graft is routed through uninjured tissue, thus reducing the problems with soft-tissue coverage and the risk of graft infection. 6, 12, 46 The disadvantages are that the adjacent vein cannot be directly inspected, and, although the injured segment of artery is often isolated by proximal and distal ligations, the injury remains in situ and subject to delayed complications. Autogenous saphenous vein is generally considered to be the best conduit for reconstructing arterial injuries, as reviewed elsewhere in this issue. The vein is usually taken from the side opposite the injury to preserve superficial venous flow on the injured side. The ipsilateral vein may be used if there is no injury or disease in the deep venous system or if the distal vein in a satisfactory graft. The saphenous vein near the ankle is often a good conduit for grafts of the popliteal and shank arteries, but the proximal vein is usually needed for reconstruction of venous injuries or to provide a sufficiently long segment for remote bypass. Polytetrafluoroethylene (PTFE) has been successful in reconstituting injured popliteal arteries. 11, 45, 46 Long-term patency is less than with autogenous vein, but graft infections have been infrequent in the absence of exposure of the graft or of osteomyelitis. PTFE is an acceptable substitute in patients with inadequate saphenous veins and in those with severe or multiple injuries in whom the time needed to harvest autogenous vein may compromise results. 11.45, 46 The choice of suture material and anastomotic technique for repairing injured vessels does not differ from the standards established for elective vascular surgery. The suture used is the smallest that will provide adequate tensile strength, and monofilament material such as polypropylene is less reactive and more hemostatic. To ensure intimal coaptation, a simple overand-over suture technique is used, and normal vessel diameter is restored. Patency of vessels whose diameter is 5 mm or less may be enhanced by spatulation of the anastomosis. Interrupted sutures are recommended in small vessels (less than 5 mm diameter) and continuous techniques in larger vessels. Venous Repair Major venous injuries accompany one-half of popliteal artery wounds and about one-fifth of shank artery wounds. 21, 48 Although the treatment of injured veins has been controversial, most authorities agree that repairs are indicated for popliteal vein injuries and for distal injuries causing venous hypertension or impeding the patency of arterial repairs (see article by Dr. Rich elsewhere in this issue). The goals of such repairs are to enhance the success of concomitant arterial reconstructions and to minimize the likelihood of postoperative venous insufficiency. 21, 37. 42, 48 A temporary reduction in arterial flow has been demonstrated after venous ligation in animals, and improvement in limb salvage with venous repair is suggested by series of patients with combined popliteal artery and vein injuries. 16, 48, 51 The relation

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between patent venous repairs and a lessened incidence of symptomatic venous insufficiency has been documented recently. 2, 28 Approximately three-quarters of local repairs and one-half of interposition grafts were patent in the early postoperative period. Asymptomatic extremities more often followed repairs shown to be patent by venography than those occluded; edema was most common after ligations. In Rich's review of 110 patients with isolated popliteal vein injuries, postoperative edema followed ligations in 51 per cent but occurred after only 13 per cent of those repaired. 43 Veins are less forgiving than arteries in regard to technical precision, and thrombosis can be expected unless vein repairs are virtually perfect and lumen size preserved. Intimal coaptation is particularly important, and special care is necessary to ensure that no adventitial tissue intrudes into the lumen. The importance of balloon catheter thrombectomy and intraoperative venography has been supported by postoperative venograms demonstrating intraluminal thrombi, separate from the site of repair, in 25 per cent of patients. 2 If ligation is necessary, late morbidity from venous stasis may be reduced by a postoperative program of prolonged elevation, graduated ambulation, and support hose. 31 Intermittent pneumatic calf compression and low-molecular-weight dextran may also reduce venous stasis after ligations or repairs. 17 Long-term anticoagulation is recommended in patients who have had complex venous reconstructions and who have no important contraindications.

ADJUNCTIVE MEASURES

Vasodilation Spasm occurs in muscular vessels after injury and operative repair, but it should not be accepted as an explanation for a circulatory deficit unless an injury has been excluded. Spasm in large vessels is not affected by pharmacologic or operative sympatholysis; it may often be overcome by direct gentle hydrostatic dilation or by using graded dilators or balloontipped catheters. . Diffuse spasm in small arteries may occur with severe injuries, especially those involving the knee and shank. Selective intra-arterial infusion of tolazoline (Priscoline) has been successful in improving distal flow in ischemic extremities after arterial repair and fracture reduction. 8, 35 This drug is an alpha-adrenergic blocker; it has a direct relaxant effect on smooth muscle and opens precapillary arteriovenous shunts. It acts by competitively blocking the vasoconstrictive receptors in the arterial wall, which results in vasodilatation. This effect is of no nutritional benefit but increases flow and thereby lessens stasis and thrombosis. A catheter for selective infusion may be introduced percutaneously or inserted through a proximal arterial branch at the time of vascular reconstruction. The tolazoline solution consists of 500 mg tolazoline with 1000 units of heparin in 1 liter of normal saline and is infused by a constant infusion pump.35 Before using tolazoline, vascular

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Table 4. Indications for "Early" Fasciotomy Extremity-swelling Severe distal musculoskeletal injury Prolonged shock Delayed restoration of flow (>4--6 hr) Combined arterial-venous injuries Ligation of popliteal or multiple shank veins

patency should be confirmed arteriographically and compartmental hypertension excluded as the cause of diminished arterial flow. Treatment of Compartmental Hypertension Increased compartmental pressure from muscle edema frequently complicates vascular injuries in the lower extremity and may threaten tissue viability or impede reconstruction. The edema may be caused by direct trauma, by proximal venous occlusion, or by the reperfusion of ischemic muscle. Operative decompression of the fascial compartments reverses this process if performed before myoneural necrosis has occurred. Clinical problems most commonly result from failures to diagnose and treat the process at a reversible stage and from incomplete operative decompression (see article by Dr. Perry elsewhere in this issue). The early recognition of compartmental hypertension may be difficult in severely injured extremities. In patients with obvious arterial injuries causing ischemia in whom the distal extremity is swollen and tense, immediate fascial decompression is needed before beginning the vascular exploration. Relieving the elevated compartmental pressure may enhance collateral blood flow and improve tissue viability until main channel flow is reconstituted. 25 Most patients do not have initial evidence of compartmental hypertension, but many will develop the problem after flow is restored. To obviate the difficult diagnosis of reversible compartmental hypertension in the postoperative period, and to avoid compromising vascular repairs, "early" fasciotomies are selectively performed during the initial operation. The criteria are based on the factors predisposing to the development of severe muscle edema (Table 4).36 If fasciotomy is not performed during the initial operation, the extremity must be carefully observed for evidence of increasing compartment pressure and circulatory compromise. Pressure monitoring may be useful in this process, although controversy exists regarding the absolute pressure that indicates the need for fasciotomy. Liberal indications for fasciotomies during the initial operation are appropriate, because the morbidity resulting from the failure to perform a needed fasciotomy is greater than that caused by the procedure. At Parkland Hospital, fasciotomies are performed in approximately 60 per cent of patients with arterial injuries below the adductor hiatus, and more than 80 per cent of these are done during the initial operation. Methods to lessen compartmental hypertension may be helpful in patients with injuries of the popliteal or shank arteries. Experimental studies have suggested that infusing hypertonic mannitol decreases the muscle edema that results from reperfusing ischemic muscle, thus reducing

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the incidence of compartmental hypertension. 3 An intravenous bolus of 100 ml of 20 per cent mannitol is given immediately before flow in restored, and this is followed by a constant infusion of 10 gm of mannitol an hour for 6 to 24 hours. The clinical efficacy of this technique has been demonstrated by a five-fold reduction in the need for fasciotomies in patients with blunt popliteal artery injuries. 46 Treatment of Associated Injuries Adjacent bone and soft-tissue injuries pose some of the most difficult problems in treating patients with arterial trauma of the knee and leg. Skeletal injuries require stabilization in about one-third of such patients. Cast immobilization interferes with wound management and with postoperative monitoring of the vascular repair. Traction often does not provide adequate immobilization of the fracture or of the vascular repair and prevents early ambulation. Internal fixation is occasionally used for simple fractures without contamination, but most injuries are best treated with an external fixation device. These instruments provide good immobilization of the bone fragments and access for inspection and treatment of soft-tissue injuries and for monitoring the distal circulation. Extensive soft-tissue trauma is a serious deterrent to limb salvage despite an appropriately managed vascular defect (see article by Doctors Rodgers and Ketch elsewhere in this issue). The principal problems are inadequate debridement of nonviable soft tissue and insufficient tissue to cover the vascular reconstruction. Thorough debridement is crucial and should not be modified to avoid a soft-tissue defect. In patients with severe injuries, it is often difficult to define the extent of muscle necrosis, and a second look in the operating room after 24 to 48 hours is helpful. 23 If difficulty covering the vascular repair is envisioned, a remote bypass may be routed through clean tissue planes, or initial coverage may be provided with porcine heterograft or homograft skin. 6, 12, 24 Definitive coverage is created in several days with musculocutaneous flaps or free tissue transfers (discussed elsewhere in this issue). The use of muscle flaps requires the preservation of appropriate muscle groups with intact neurovascular innervations, and this is most successfully accomplished by involving the reconstructive surgeons in the initial operation. SPECIFIC INJURIES

Popliteal The medial approach to the popliteal vessels is favored for most trauma explorations because it can be easily extended for access to the superficial femoral proximally or the tibioperoneal trunk distally. In addition, saphenous auto grafts are more easily obtained with the patient supine. The extremity is supported at the knee in slight flexion with the hip abducted and externally rotated. If there is evidence of compartmental hypertension in the ischemic extremity, an initial fasciotomy can be completed in a few minutes, which enhances collateral flow during the time required for definitive reconstruction. 25

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Popliteal a.

Gastrocnemius m. Hamstring muscles

Figure 2. Operative exposure: Popliteal artery.

The incision is made along the medial aspect of the lower thigh, parallel to and just behind the tendon of the adductor magnus (Fig. 2). During the superficial dissection, care is required to avoid injury to the adjacent saphenous vein and nerve. Depending on the level of exploration, the sartorius muscle is divided or retracted anteriorly or posteriorly to provide maximum exposure. The artery is found by displacing the semimembranosus muscle posteriorly and dissecting the space between it and the adductor magnus tendon. Through this approach, the artery is the most superficial of the neurovascular structures, the vein and nerve lying subjacent, laterally, and posteriorly. More distal exposure may be obtained by dividing the medial head of the gastrocnemius and the tendons of the semimembranosus, semitendinosus, and gracilis muscles. Restoration of arterial and venous flow is the essential basis of successful limb salvage and is best accomplished by priority revascularization. If more urgent injuries require treatment, or if extensive fractures must be reduced first, an indwelling shunt may be inserted to maintain flow. Arterial resection is usually necessary, and adequate margins are particularly important in blunt and high-velocity missile injuries. End-to-end anastomosis may be possible, but vein grafts should be used readily to avoid inadequate resections or anastomotic tension. Autogenous vein interposition or bypass grafts were used for reconstruction in more than 80 per cent of popliteal arterial injuries in recent series. 34• 52 During the repair, the knee is best placed in an unflexed position so that the vessel will be of the proper length when the limb is fully extended. Completion arteriography is essential to detect technical defects at the anastomosis, missed additional injuries, and residual thrombus. It is important to obtain patency of at least two of the three arteries distal to the popliteal vessel. Restoration of venous flow is perhaps more important in the popliteal area than elsewhere to enhance patency of arterial anastomoses and lessen the likelihood of late venous stasis. 42. 43. 48 Extensive venous injuries may require interposition grafts; these are recommended unless the additional

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Table 5. Management Dicta for Popliteal Injuries Avoidance of lower extremity "reimplantation" Expeditious diagnosis Despite intact pulses or capillary filling Arteriography of suspicious injuries Avoid undue attention to skeletal injury Early systemic anticoagulation unless contraindicated Urgent and complete revascularization "Routine" balloon catheter thrombectomy Vessel repair before bone reduction Adequate debridement of injured vessel Liberal use of autogenous vein grafts Repair of venous injuries "Routine" completion arteriography Liberal, though selective, fasciotomy Thorough debridement of nonviable soft tissue Appropriate use of myocutaneous flaps

time imposes substantial risks. Venous thrombectomy also may be needed to open the system. Completion venography should be considered to ensure the patency of venous reconstructions and exclude intraluminal thrombi. Fasciotomies are often necessary to restore and preserve adequate distal flow and are performed in three-quarters of patients with combined popliteal arterial and venous wounds and in all such injuries resulting from blunt trauma. 50 Important concepts that may improve overall limb salvage have evolved from a review of no popliteal arterial injuries. 48 The individual points were derived from study of repeated technical or judgmental errors, as well as of beneficial maneuvers that appeared to improve or simplify patient management. These concepts, set forth in the foregoing discussion, are summarized in Table 5.

Tibial and Peroneal The indications to reconstruct, rather than to ligate, injured tibial and peroneal arteries are not well defined. Patency should usually be maintained in two of the three distal vessels, and all injuries of the tibioperoneal trunk need repairs. 21 Injuries of single distal arteries are repaired if local means suffice; otherwise ligations are performed. Interposition grafts are infrequently indicated. Vertical incisions are used because extensions may be required for vascular control and repair. For proximal injuries, the lower portion of the popliteal incision is extended distally (Figs. 2 and 3). The tibioperoneal trunk is exposed by retracting the medial head of the gastrocnemius and incising the tibial attachment of the soleus muscle (Fig. 3). The proximal posterior tibial and peroneal arteries may be exposed through a medial approach distal to that used for the tibioperoneal trunk (Fig. 4). The proximal portions of all three shank vessels may be exposed through a lateral incision with anterior reflection of the peroneus muscles and resection of part of the fibular shaft (Fig. 5). Isolated anterior tibial injuries are approached through a lateral incision between the tibalis anterior and extensor hallucis longus muscles (Fig. 6). The distal posterior tibial artery

803

POPLITEAL AND SHANK ARTERIAL INJURY

Anterior tibial a.

Tibialis posterior

m. .--=C;7'--,.!f--r--!l--

Fie x0 r hall uc is longus m.

Soleus m.

Saphenous v. Tibioperoneal trunk a.

Figure 3. Operative exposure: Tibioperoneal trunk.

is easily located immediately beneath the muscular fascia through a medial incision behind the edge of the tibial shaft. Success of repair is enhanced by small-vessel techniques including optical magnification, spatulation, and interrupted fine sutures. In patients with extensive musculoskeletal trauma, extra-anatomic autogenous vein bypass to a tibial vessel beyond the principal injury may be indicated. 12 Completion arteriography is usually advisable if the repair is being performed to relieve ischemia. Restoration of venous How is important for proximal injuries and those with extensive soft-tissue destruction and compromised collateral venous How. Fasciotomies are frequently necessary

Tibialis posterior m. Soleus m.

1L.~--ij--;1f- Peroneal a.

Figure 4. Operative exposure: (Medial) Proximal posterior tibial and peroneal arteries.

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Anterior tibial a.

Superficial peroneal n. Fibula

Tibial a. Tibialis posterior m. Figure 5. Operative exposure: (Lateral) Shank arteries mid-leg.

and are especially important in blunt injuries and those with profuse intracompartmental bleeding.

POSTOPERATIVE CARE Patients with vascular injuries of the knee and leg must be observed closely in the postoperative period. Thrombotic occlusion and compartmen-

Tibialis anterior m.

Extensor digitorum longus m. Extensor hallucis longus m.

Figure 6. Operative exposure: Anterior tibial artery.

POPLITEAL AND SHANK ARTERIAL INJURY

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tal hypertension are the most common early complications-both require immediate reoperation. Ph'ysical and Doppler examinations are the best means of postoperative monitoring; arteriography is performed only for specific indications. Perception of light touch and normal motor functions are good indicators of adequate perfusion, but skin temperature and color may be misleading. An unexplained fever, tachycardia, or distal sensory or motor deficits may be caused by nerve or muscle ischemia despite viable overlying skin. To exclude this possibility, it may be necessary to incise the skin and fascia and directly inspect the underlying muscle. Infection is a serious threat to the patient with a vascular injury and often suggests residual necrotic tissue. In patients with extensive soft tissue injuries, a second look in the operating room is planned every 24 to 48 hours until it is clear that only healthy tissue remains. Anticoagulation generally is not used after repair of arterial injuries. If arterial reconstruction is technically competent, there is no need for anticoagulation; if the repair is technically imprecise, no amount of heparin will sustain patency. Aspirin has been recommended to retard platelet activity after infrapopliteal arterial repairs. 12, 22 The role of anticoagulation in venous reconstruction for trauma is also controversial, but, primarily on the basis of experience with deep venous thrombosis, anticoagulants are often used for 6 weeks, especially after complex repairs,

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46. Shah OM, Naraynsingh V, Leather RP, et al: Advances in the management of acute popliteal vascular blunt injuries. J Trauma 25:793, 1985 47. Smith F, Elliott JPM, Hageillan JH, et al: Acute penetrating arterial injuries of the neck and limbs. Arch Surg 109:198, 1974 48. Snyder WH III: Vascular injuries near the knee: an updated series and overview of the problem. Surgery 91:502, 1982 49. Snyder WH III, Thal ER, Bridges RA, et al: The validity of normal arteriography in penetrating trauma. Arch Surg 113:424, 1978 50. Snyder WH III, Watkins WL, Whiddon LL, et al: Civilian popliteal artery trauma: an eleven-year experience with 83 injuries. Surgery 85:101, 1979 51. Sullivan WG, Thornton FH, Baker LH, et al: Early influence of popliteal vein repair in the treatment of popliteal vessel injuries. Am J Surg 122:528, 1971 52. Weimann S, Nicolo MS, Sandbichler P, et al: Civilian popliteal artery trauma. J Cardiovasc Surg 28:145, 1987 53. Whitman GJR, McCroskey BL, Moore EE, et al: Traumatic popliteal and trifurcation injury--determinants of limb salvage. Am J Surg 154:681, 1987 54. Yeager RA, Hobson RW II, Lynch TG, et al: Popliteal and infrapopliteal arterial injuries: differential management and amputation rates. Am Surg 50:155, 1984 Department of Surgery University of Texas Southwestern Medical Center 5323 Harry Hines Boulevard Dallas, Texas 75235