Conventional radiography remains the imaging standard for the evaluation of long bones showing obvious deformity, instability, palpable crepitus, pain, and swelling. For periarticular regions, conventional x-rays are indicated for deformity, instability, decreased range of motion, pain, and swelling. The Ottawa ankle and knee clinical prediction rules add considerable precision to specificity.91,92,93
For long bones (Fig. 15-38), two orthogonal views are obtained, including an AP view and lateral projection centered at the midshaft. Projections should include both the proximal and distal joints. Joints should be imaged with two orthogonal views at a minimum, with additional optional one or two oblique views, centered at the midportion of the articulation (Figs. 15-39, 15-40, 15-41, 15-42, 15-43).
33-year-old male with a Monteggia fracture. Lateral radiograph of the forearm demonstrates a comminuted fracture of the mid ulnar diaphysis (arrow) with associated anterior dislocation of radius at radiocapitellar articulation (arrow head).
Periarticular fracture: coronoid process fracture of elbow. (A) Anteroposterior (AP) radiograph of left elbow shows displaced coronoid process (arrow). Elsewhere, joint appears congruent. (B) Lateral view of left elbow shows tip of coronoid process fracture (arrow). Coronoid process fractures can be graded by amount of coronoid process involved, such that larger coronoid process fracture fragments are more likely to result in elbow instability. (C) Axial computed tomography (CT) obtained because mismatch between radiographic and clinical findings of instability shows highly comminuted fracture of coronoid process (arrows). Radial head (R) and olecranon process (O) appear normal. (D) Sagittal CT reformation shows nearly all the coronoid process is involved in fracture. Secondary congruence between trochlea and olecranon–coronoid process is fair. (E and F) Three-dimensional “surface-rendered” CT reformations more graphically demonstrate transverse and distal extent and displacement of coronoid process fracture.
Periarticular injury: shoulder dislocation. (A–C) Anterior dislocation sustained by a 52-year-old struck by falling tree on his back. (A) An anteroposterior (AP) radiograph with medial location of humeral head relative to glenoid (circle). (B) Postero-oblique radiograph of humeral head and glenoid (dotted line). Note that amount of overlap of scapula is less on this posterior oblique view than it is on anterior view (A), characteristic of anterior dislocation. (C) An axillary view; shows anterior location of humeral head relative to glenoid (upward pointing arrow and circle, respectively) on axillary lateral view. (D and E) Posterior dislocation sustained in a 42-year-old man who fell during a seizure. Posterior oblique radiograph (D) shows overlap of glenoid (circle) and medial aspect of humeral head (dotted line). (E) An axillary projection that shows the location of the humeral head posterior to glenoid (oval). Posterior margin of the head is denoted by downward pointing black arrow. Three downward pointing white arrows show impaction on anterior margin of humeral head, so-called trough fracture or reverse Hill–Sachs deformity.
Periarticular fractures: intra-articular intercondylar distal femur fracture. This 20-year-old man was involved in a high-speed motor vehicle crash as a belted driver. (A) Anteroposterior (AP) radiograph of knee shows transverse T-type fracture of distal supracondylar femur, with intra-articular extension into intercondylar notch (arrows). (B) Lateral radiograph of knee shows transverse supracondylar component (arrow), from which femoral condyles have dissociated. In addition, lateral femoral condyle shows coronal plane, comminuted fracture of posterior aspect of condyle (arrowheads). In up to 40% of intra-articular intracondylar fractures caused by high-energy mechanisms, such coronal plane fractures (Hoffa’s fracture) may be overlooked. (C) Axial computed tomography (CT) shows a sagittal plane fracture extending into midportion of trochlea of the patellofemoral joint and a comminuted coronal plane fracture of posterior aspect of lateral femoral condyle (arrow). (D) Coronal plane reformation from axial CT shows T-type intra-articular fracture with dissociation of medial and lateral femoral condyles (white lines). Asterisk marks developmental variant, nonossifying fibroma. (E) Sagittal reformation from axial CT in central portion of lateral knee joint compartment shows coronal plane fracture of posterior femoral condyle (Hoffa’s fracture) as marked by arrow. Asterisk notes nonossifying fibroma, a benign developmental variant.
Periarticular fractures: tibial plateau fracture (Schatzker 2). This 46-year-old man fell on the stairs. (A) Anteroposterior (AP) radiograph of knee shows valgus angulation due to collapse of lateral femoral condyle into a split depressed fracture of tibial plateau (arrows). (B) Axial image from computed tomography (CT) shows depressed left (asterisk) and split (arrows) portions of split depressed fracture. Note extension of comminuted fracture lines into medial tibial plateau across posterior aspect of proximal tibia and into intercondylar eminences, where anterior eminence (A) is minimally displaced. (C) Coronal reformation from axial CT shows split (arrow) and depressed (asterisk) portions of Schatzker type 2 fracture. Also note apparent elevation of anterior tibial eminence (A), on which anterior cruciate ligament inserts. Less striking step-off is seen in central portion of medial tibial plateau. (D) Three-dimensional CT reformation graphically demonstrates depression and lateral displacement of articular surface and lateral rim of tibial plateau, respectively. Also shown on this view is fracture of proximal fibula.
Periarticular fractures: calcaneus and Lisfranc fractures of midfoot. This 51-year-old restrained driver in a high-speed motor vehicle crash sustained multiple extremity and torso injuries. (A) Lateral conventional radiograph shows intra-articular fracture of calcaneus (upward pointing arrow denotes primary fracture plane; asterisk shows double density of central lateral fragment of posterior subtalar joint of calcaneus). Downward pointing arrow shows displacement of one of the metatarsal bases with an adjacent cuneiform fracture. (B) Axial computed tomography (CT) image at level of base of sustentaculum tali shows varus deformity through primary fracture (arrow). Secondary fracture plane extends toward anterior process (bracket). It is important to note continuity of cortex of medial wall of anterior process, as it influences distal extent of necessary fixation. (C) Sagittal reformation from axial CT shows primary fracture plane (upward arrow) with centrolateral fragment rotated into its superior extent. (D) Coronal reformation shows comminuted fracture of posterior facet of calcaneus due to bursting of body by lateral process (LP) of the talus. Centrolateral fragment is shown by asterisk. White arrow denotes lateral dislocation of peroneal tendons from peroneal groove in posterior fibula. (E) Axial CT at level of sinus tarsi, soft tissue window, shows lateral and anterior dislocation of peroneal tendons surrounded by hemorrhage and edema (white arrow). (F) Three-dimensional reformation from axial CT, medial oblique projection, shows divergent dislocations of great toe and third to fifth metatarsal bases (arrows).
Analysis of the long bone should allow assessment of the direction of the force that created the fracture pattern (eg, twisting injuries result in spiral fractures; bending injuries result in wedge fractures). In general, higher-energy injuries tend to be more comminuted and displaced. If there is a mismatch between the apparent amount of comminution and the reported energy of the injury, osteoporosis or otherwise pathological bone should be suspected. The degree of displacement and angulation of the predominant fracture fragments, as well as fracture line involvement of an articular surface, should be noted.
Periarticular regions should be evaluated for fracture involvement as well as for partial or complete loss of congruity of the joint. The appearance of a superimposed white line due to overlapping of bones may indicate a dislocation and disruption of expected alignment of adjacent articulating structures.
Careful attention to soft tissues (eg, focal swelling, obliteration of normal fat pads, joint effusions) is helpful for subtle or otherwise occult fractures (eg, elbow, knee, and wrist). A search for foreign bodies in soft tissue in the setting of an open fracture or soft tissue injury should be performed.
Computed Tomography of Appendicular Joints
CT of appendicular joints, particularly the shoulder, supracondylar femur, tibial plateau, pilon, midfoot and calcaneus, is indicated for “displaced” intra-articular fractures (eg, 1–2 mm at the wrist or scapula, and glenoid, 5–10 mm at the tibial plateau) or unstable fracture patterns (Figs. 15-37, 15-38, 15-39, 15-40, 15-41). CT is a valuable surgical planning tool and is very helpful in the detection of otherwise occult fractures, particularly of the midfoot.
In most patients, CT should be performed after provisional placement of traction or reduction, if feasible. Because acquisition of isotropic image data of modern MDCT scanners allows for reconstruction of images in any conceivable plane, the joint in question no longer needs to be precisely positioned in the CT scanner gantry. Thus, “axial” images of a joint are not necessarily oriented in the axial plane of the body, but instead are oriented in the “axial” plane of the joint. Orthogonal images in both the sagittal and coronal planes are reconstructed from the joint specific axial plane at 1–3-mm slice thickness.
Use of traction prior to imaging allows ligamentotaxis to indirectly reduce fracture fragments and support indirect assessment of the integrity of soft tissue attachments to major bony fragments. Specifically, bone fragments that do not move or reduce on stretch are presumed to be no longer attached to soft tissue and may require debridement or direct repositioning. In addition, CT facilitates the assessment of intact bone and the integrity of subchondral bone (eg, need for bone grafting).
Peripheral Vascular Injuries
Vascular injuries in the extremities comprise between 40–75% of vascular injuries seen in civilian trauma centers, with a majority of these (~2/3) involving the femoral or popliteal arteries. Approximately three-fourth of peripheral vascular injuries are the result of penetrating trauma, with 70–80% secondary to projectiles such as gunshot wounds and shrapnel. Fatal exsanguination, multiorgan failure secondary to hemorrhagic shock, and limb loss are catastrophic consequences of peripheral vascular injuries, thus rapid identification and appropriate triage are of paramount importance. Vigorous or pulsatile external active hemorrhage, a rapidly expanding hematoma, or loss of distal pulses mandate emergent operative exploration.94
The imaging strategy for patients with suspected peripheral vascular injuries depends on a variety of factors that are primarily related to clinical presentation, hospital course and to associated injuries, mechanism of injury, and signs of circulatory shock. Imaging modalities available include catheter angiography, CT angiography, Doppler ultrasound, and MR angiography (MRA).
Doppler ultrasound may be a useful adjunct but is not widely used, primarily because of its decreased sensitivity and accuracy for peripheral vascular injuries when compared to catheter angiography. This, coupled with the operator dependent nature of the examination and limited visualization of the entire vascular system for a variety of reasons (such as external fixator devices, overlying split or cast material, and associated soft tissue injuries and gas), make the utility of Doppler ultrasound for peripheral vascular injuries quite limited.
MR angiography is useful for the assessment of chronic peripheral vascular disease, but is not widely used in the acute setting for the following reasons: (1) may not be available at all centers at all times of the day; (2) it is technically challenging to effectively manage severely traumatized patients while they are in the MR magnet; (3) the presence of metallic foreign bodies may limit patient and operator safety; and (4) even if not ferromagnetic, foreign bodies may still cause extensive artifact obscuring the adjacent soft tissues. Thus, CT or catheter angiography are the primary imaging choices for patients with extremity injuries and suspected peripheral vascular injuries.
CT Angiography for Suspected Peripheral Vascular Injuries
CT angiography is a useful adjunct for suspected peripheral vascular injuries in patients without indications for immediate surgical exploration. As stated previously, CT is readily available, quick, convenient, noninvasive and reliable. In addition, CTA can be easily integrated into the imaging work-up of a traumatized patient, performed either as a stand-alone examination or integrated as part of a whole body CT for polytrauma. CTA has high sensitivity, specificity and accuracy when compared to catheter angiography (which remains the reference “gold” standard). In addition, CT capabilities allow for global evaluation of the adjacent structures and can thus be used to detect and characterize associated nonvascular injuries. The inability to immediately perform interventions on an injured vessel is a major limitation of CTA compared to catheter angiography.
The overall performance of CTA for peripheral vascular injuries compared to catheter angiography is certainly a concern for the trauma surgeon, as there is very little tolerance for missed or mischaracterized vascular injuries. A meta-analysis by Jens et al95 pooling data from 11 studies from both the radiology and surgical literature and using a variety of scanner types, documented that peripheral CTA for extremity vascular injuries had a sensitivity of 96.2% and specificity of 99.2% compared to catheter angiography. The rate of nondiagnostic CTA examinations was 4.2% in this meta-analysis. Thus, in patients without indications for immediate surgical exploration, CTA is useful to exclude peripheral vascular injuries and to characterize injuries that are present.
The CTA signs of a vascular injury include pseudoaneurysm, active bleeding, occlusion, intimal injury, dissection, and arteriovenous fistula. Imaging findings that raise the likelihood of an injury include a perivascular hematoma, a vessel within a projectile wound tract, and projectile fragments within 5 mm of a vessel. The latter two findings should prompt further investigation with catheter angiography.
Extremity CTA should be performed using MDCT with thin section acquisition, peripheral IV access or a power injectable central line, a high contrast injection rate (4–5 mL/sec) and be acquired during the systemic arterial phase. Images are reconstructed in the true axial plane to the long axis of the extremity at 1–3-mm slice thickness, with additional sagittal and coronal images reconstructed with respect to the axial plane. Coronal maximum intensity projections (MIP, or thick slab images) at 5–10-mm slice thickness are extremely valuable in displaying vessels along their long axis using a relatively small number of slices. Thin images should be reviewed, as well, as small intimal vascular injuries may not be apparent on MIP images due to volume averaging. Liberal use of a 3D volume viewing station is encouraged, as some vascular injuries may be best displayed on nontraditional planes.
It should be noted that vascular injuries near highly mobile joints, such as the knee, are poorly treated with endovascular techniques. Thus, the decision to image with CT angiography over catheter angiography must be weighed against patient stability and the need for urgent surgical vascular repair. Despite this, the wide availability of stent grafts has also increased the utilization of angiography as a prelude to nonoperative management of some clinically significant vascular injuries.
Catheter angiography remains the reference “Gold Standard” for the definitive evaluation of arterial blood vessels for injury, as well as identifying active arterial hemorrhage, false aneurysms, and arteriovenous fistulas. While CT angiography is frequently favored for the initial imaging of many traumatic vascular lesions in stable patients, it is limited by the inability to immediately intervene in the event of a positive study. CT angiography performance is very high, but not yet as accurate as catheter angiography. Catheter angiography is utilized as a problem solving tool for equivocal CT examinations and for definitive therapy of some acute vascular conditions.
There are many advantages of catheter angiography. It allows simultaneous detection and treatment of a wide variety of traumatic vascular injuries. It is a very specific method of identifying bleeding at the sub-millimeter diameter of vessel. It can evaluate many sites of bleeding simultaneously. It has an excellent safety record, especially when using iso-osmolar nonionic contrast agents, coaxial micropuncture access, digital subtraction techniques, coaxial microcatheters, and steerable guidewires.
The disadvantages of catheter angiography are cost, the delay necessary to assemble the interventional radiology team (comprised of radiologists, technologists, and nurses), the lack of suitability as a screening test for most traumatic conditions, and the risks of radiation exposure. Technical expertise is limited to predominantly subspecialty-trained interventional radiologists, although endovascular surgeons and cardiologists may develop this expertise on an individual basis. These disadvantages are magnified when the likelihood of injury is low. Thus, noninvasive vascular techniques such as CT angiography should be explored under controlled studies to further assess their accuracy and appropriateness in such situations.
Transcatheter Endovascular Therapies
Endovascular techniques have become a broadly accepted way of controlling traumatic hemorrhage for a variety of reasons. Catheter-based hemostasis allows precise control from a remote site that avoids exacerbation of venous hemorrhage, introduction of pathogens, and hypothermia that may result from open exposure. It is especially valuable for hemorrhage that is remote or hidden from view and requires laborious time-consuming exposures or that is the result of multiple small bleeding sites that are not easily detected or controlled during operative exploration.
Endovascular techniques include embolization, stenting, stent grafting, and temporary balloon occlusion and may be definitive in nature or an adjunct to operative exposure. The methods of embolization include particulate or microcoil embolization of small vessels, proximal and distal control of a bleeding vessel, and coil occlusion to cause selective temporary hypotension of the bleeding zone.
Stenting, which facilitates blood flow beyond an injury, has largely been replaced by covered stent grafts that exclude lacerations, transections, and arteriovenous fistulae while maintaining flow through the conduit. Endografts are made of a variety of porous materials such as expanded polytetrafluoroethylene and are reinforced by a metallic skeleton that apposes the stent graft to the native artery. Reports of midterm patency, while limited at this time, are beginning to show that these are durable options to vascular repairs.
Contraindications to endovascular techniques are highly dependent on skills, teamwork, and hemodynamics; however, there are some injuries that are difficult for rapid surgical control and endovascular techniques have a role, even in the unstable patient.
Arch Angiography for Acute Blunt-Force Traumatic Aortic Injury
Screening and diagnostic arch angiography for blunt traumatic aortic injuries has largely been replaced by chest CT angiography, particularly with the widespread availability of MDCT technology.66 Arch angiography, however, does have a role for the evaluation of equivocal findings on chest CTA and for potential endovascular stent graft therapy. This is particularly true if there is a suspected injury to the ascending aorta or aortic root seen on CT. If patients are going directly to angiography for evaluation of disruptions of the pelvic ring and the mediastinum is not normal on a chest x-ray, catheter arch angiography is the preferred “screening” modality; otherwise, CT is the preferred modality. Modern CT angiographic techniques are quite exquisite in demonstrating aortic injuries as well as providing coronal and sagittal reformations that can illustrate the important relationships and variants necessary for surgeons to create a treatment plan. Among selected patients sustaining aortic injury who are not operative candidates, endovascular stent grafts have been advocated as either temporizing or definitive therapy.
Typically, a 5 French pigtail catheter is guided to the ascending aorta via a femoral arterial approach. Patients are positioned and imaged in both 35° right anterior oblique (RAO) and left anterior oblique (LAO) projections, using injection rates of approximately 25–30 mL/s for a 40–60 mL volume (depending on hemodynamic status) and positioning to include the great vessels and diaphragm.
The arteriographic appearance is classical. Linear filling defects indicate torn and ruffled intimal lining, with expansion of the lumen (typically at the ligamentum arteriosum) indicating the presence of a pseudoaneurysm (Fig. 15-44). The tear of the aortic wall may be segmental or circumferential, and is sometimes associated with distal narrowing of the contrast column (pseudocoarctation). Minimal aortic injuries, as discussed earlier in this chapter, may be very difficult to visualize angiographically, and a “negative” aortogram following a positive chest CTA for a minimal aortic injury will not eliminate the diagnosis.
Traumatic aortic pseudoaneurysm. A 30-year-old male following high-speed motor vehicle accident. Left anterior oblique (LAO) digital subtraction arch aortogram shows traumatic aortic pseudoaneurysm extending proximal to the left subclavian artery. Of note, the aortic diameter and the distance from the left subclavian artery are important when considering endovascular therapy.
Associated mediastinal vascular injuries should also be identified. Injuries of the arch arteries may occur instead of, or in association with, an aortic injury. Bleeding from the internal mammary or the intercostal arteries may be easily overlooked without diligence.
Hepatic Angiography for Blunt-Force Lacerations
Visceral catheter angiography is appropriate to evaluate hepatic lacerations (Fig. 15-45), particularly in patients with a labile hemodynamic status, or those with active extravasation or vascular abnormalities as seen on a contrast-enhanced CT. Visceral catheter angiography may have a role after a “damage control” operation. Gross hemodynamic instability and profound shock, however, usually mandates urgent celiotomy.
Liver laceration. (A) CT of the upper abdomen reveals a Grade V liver laceration with pseudoaneurysm of the right hepatic lobe in this 18-year-old male status post-high-speed MVA. (B) Right hepatic angiogram identified the pseudoaneurysm. Note the size of the feeding vessel in relation to the 5 French diagnostic catheter. Selective coil embolization was performed through a microcatheter. When selective catheterization is not possible, the liver is quite tolerant of wide arterial embolization due to the dual blood supply provided the portal veins are patent.
On CT, hepatic fracture lines that traverse the hepatic triad result in bleeding more often than those that run parallel to the triad. Contrast extravasation on CT tends to be associated with a positive arteriogram, but the decision to use angiography should primarily be based on clinical status rather than the CT appearance. Lack of enhancement of liver segments on CT is a very important finding, as these regions represent an intraparenchymal hematoma, occlusion of the portal triad, or injury of the hepatic outflow from that segment. It is vital to distinguish nonenhancement from a hematoma, which can be challenging. A large hepatic hematoma pushes the hepatic fragments away from each other and lacks hepatic vessels. If the area of nonenhancement has vessels running through it, it suggests an occlusion of the portal vein and hepatic artery or injury to a hepatic vein. Therefore, CT nonenhancement of the liver is an indication for angiography to confirm such injuries and to control arterial hemorrhage. As surgical exploration of damaged hepatic veins may be quite difficult, hepatic embolization and observation of a nonbleeding hepatic venous injury can be lifesaving. And, as noted earlier, hepatic angiography has an important role in the management of penetrating liver injuries that are isolated to the liver.
Selective catheterization of both the celiac trunk and the superior mesenteric artery (SMA) is essential due to the high rate of hepatic vascular variants, particularly the aberrant replaced right hepatic artery from the SMA. Imaging should be continued through the late portal venous phase to evaluate for slowly bleeding vessels. There should be careful inspection for abnormal parenchymal enhancement and intrahepatic portal venous filling, as these are features of hepatic arterial-portal venous fistulae, which can easily be overlooked.96
Critical findings include arterial extravasation, spasm and occlusion, or shunting and fistula to portal or hepatic venous structures. Embolization of discretely abnormal vessels can be performed using a number of methods. A diffusely abnormal parenchymal injury with arterial bleeding may be safely embolized with Gelfoam due to the dual blood supply of the liver (hepatic arterial and portal venous). Embolization of hepatic arteries in the absence of portal flow increases the risk of developing an infarction or abscess. Depending on the location of bleeding and on the difficulty with catheterization, particulate embolization is the fastest technique; however, single microcoil embolization is preferred if time and circumstances allow. While formation of a postprocedure abscess is a complication of embolization, outcomes are favorable by integrating percutaneous image-guided drainage into the scheme.
Splenic Arteriography for Blunt-Force Lacerations
A patient who is hemodynamically unstable is not a candidate for angiography and embolization. Patients with splenic injuries diagnosed on CT are candidates for nonoperative management with overall good salvage rates, particularly when combined with splenic angiography and embolization.76,97 When CT demonstrates active arterial extravasation or a parenchymal vascular abnormality (such as an intra-parenchymal pseudoaneurysm), one should consider angiography, as these are independent predictors of failure of nonoperative management. It is thought that there was poor correlation between the CT grading system and outcome of treatment, as many Grade IV injuries can be observed, and some Grade I injuries become worse, rebleed, and require definitive procedural therapy; however, there is emerging evidence that a CT-based grading schemes, in combination with clinical parameters (such as AIS), may be helpful for patient triage.98,99 The treatment algorithms for patients with splenic injuries in the absence of active bleeding or other vascular lesions varies by institution. Some centers observe (ie, bed rest) most Grade I injuries, some advocate liberal use of angiography for triage of most other CT-diagnosed splenic injuries (such as those Grade III or higher), some centers advocate angiography in patients with a significant hemoperitoneum or transient hypotension. But in general, patients with high-grade injuries on CT should be imaged by angiography early to avoid transfusion or delayed rupture. The absence of arteriographic extravasation is a highly reliable predictor of successful nonoperative therapy regardless of injury grade. Identification of active arterial extravasation is the standard indication for endovascular treatment.
Diagnostic angiography of the celiac trunk is followed by selective splenic artery catheterization with a 5 French catheter. If splenic artery anatomy permits, and a solitary pseudoaneurysm or focus of extravasation is seen, distal coil embolization at the site of injury can be attempted. This is especially true in a patient in whom the extravasation extends beyond the splenic capsule into the peritoneal cavity. One should note that distal superselective embolization is associated with the development of more postprocedure splenic infarctions and abscess, though these complications are uncommon. Finally, most patients have tortuous splenic arteries and most extravasations are multiple.
Diffuse intrasplenic extravasation is far more common, and superselective occlusion of these multiple sites would be very time-consuming and less effective. Also, the splenic tortuosity that results from medial displacement of the spleen by the perisplenic hematoma often prevents rapid catheterization (Fig. 15-46). In such cases, embolization of the proximal splenic artery by coils or other occlusion devices placed distal to the dorsal pancreatic branch and proximal to the pancreatic magna branches is advocated to reduce the arterial pressure head at the injury site while allowing perfusion through collateral vessels. Such collaterals prevent splenic infarction by maintaining splenic perfusion through connections between the left gastric and the short gastric arteries, between the dorsal pancreatic artery and the pancreatica magna branches, between the right and left gastroepiploic vessels, and others.
Splenic intraparenchymal false aneurysms. Digital subtraction angiogram of the splenic artery reveals multiple focal extravasations in this 56-year-old male status post-MVA. Selective embolization is not desirable because so many vessels are injured and selective catheterization would be difficult due to splenic artery tortuosity. In such cases proximal splenic artery coil embolization proximal to the pancreatic magna branch is usually successful in controlling this hemorrhage.
Complications are uncommon when proximal splenic artery embolization is performed. A poorly selected coil size may result in hilar occlusion if the selected coil is too small and migrates distally. Too large coils may migrate proximally to occlude the celiac axis or embolize into the aorta. As noted earlier, distal microembolization bypasses the collateral circulation and results in more loss of immune function. Occlusion of the pancreatic branches may result in pancreatic necrosis and pancreatitis, though this complication is rare and can be avoided by careful review of the angiographic images if main splenic artery embolization if considered.
Interventions for Renal Trauma
Many renal injuries are usually well-tolerated and do not require angiography, especially when caused by blunt trauma. Initial nonoperative management of blunt renal injuries with an intact pedicle is the current accepted management standard. High-grade injuries that result in massive hemorrhage are usually managed by nephrectomy. Angiography with intent to embolize bleeding is appropriate for hemodynamically stable patients. Angiography is recommended for patients with CT evidence of a major renal injury and ongoing blood loss or persistent gross hematuria. Peripheral wedge-shaped regions of nonenhancement on CT suggest a segmental or distal renal artery injury, often due to avulsion injury or intimal stretch resulting in distal platelet embolization. Penetrating renal injuries are more aggressively approached by angiography if nonoperative management is undertaken. Large perinephric hematomas, areas of nonenhancement, and active bleeding on CT warrant angiography following penetrating trauma.
Aortography is helpful to assess injury of the origin of the renal artery, to exclude renal parenchymal injury perfused by accessory renal arteries, and to look for associated bleeding sites. A selective renal arteriogram using a 5 French catheter is then performed. Most injuries will require use of a coaxial microcatheter and embolization of small branches. Coils are preferred as they can be carefully placed to prevent infarction of adjacent noninjured renal tissue, but surgical gelatin pledgets can be used, as well. Because renal branches are end vessels with little collateralization, infarction is likely, and the goal is to reduce these infarctions to a minimum.
The treatment of vascular injury in the renal pedicle continues to be a vexing problem, especially since delays in revascularization usually result in a renal infarction or renovascular hypertension. Partial wall injuries that result in a pseudoaneurysm or segmental infarction often went unrecognized prior to the widespread use of CT. Such injuries are routinely detected before complete arterial thrombosis and renal infarction occurs. Therefore, arteriography is indicated when an injury in the renal artery is suspected. When such injuries are detected, treatment options are many, including operative revascularization, antiplatelet therapy and observation, and the application of covered stent grafts. Stent grafts can effectively seal full thickness injuries and cover exposed media that results in embolic infarctions. While long-term follow-up of series of these patients is lacking, the midterm (1–5 years) patency of stent grafts throughout the body remains high (Fig. 15-47).
(A–D) Renal artery injury. A 56-year-old man fell from a height of about 10 m. (A) During CT evaluation inhomogeneous enhancement of the spleen was detected. Central perinephric hemorrhage (asterisks) and irregularity of the renal artery (arrow) were seen. (B) Coronal reformation shows irregularity of the renal artery and thickening of its wall. (C) Aortography showed irregular enlargement of the proximal renal artery near the ostium (circled). Slight extravasation was seen on the later images. (D) Therefore, a stent graft was placed over the area of injury. The vessel wall was then smooth, and no extravasation was seen. Two-year follow-up arteriography showed continued patency and no stenosis.
Pelvic fractures are potentially life-threatening injuries that are caused by high-energy impact trauma and account for about 3% of skeletal injuries. They are the third most common lethal injury following motor vehicle crashes. The majority of patients with pelvic fractures do not require massive transfusion as bleeding in most cases is likely to be venous or osseous in nature and often self-limited. Radiological intervention is not commonly needed in patients with routine pelvic fractures. Severe hemorrhage, however, occurs in 3–10% of patients, and mortality rates may be as high as 50% in patients with unstable pelvic fractures. Thus, the use of angiography in patients with pelvic fractures is highly dependent on the hemodynamic status, the type of pelvic fracture pattern, the transfusion requirements, and the presence or absence of hemoperitoneum.
Blunt pelvic fractures with crushing or shearing tear the small branches of the internal iliac artery that accompany ligaments, muscles, and tendons. Injuries tend to be multiple and bilateral, and from several branches. In addition, bony fragments can penetrate or perforate vascular structures. Examples include a fracture of the superior pubic ramus injuring the internal pudendal or obturator artery, a fracture of the iliac wing through the sciatic notch injuring the superior gluteal artery, and disruption of the sacroiliac joints injuring the lateral sacral arteries.
Most of the indications for angiography in blunt pelvic trauma have remained the same for more than 30 years, and include the following:
Hemodynamic instability in a patient with a pelvic fracture with no or little hemoperitoneum detected by FAST or diagnostic peritoneal lavage
Pelvic fracture and transfusion requirement of greater than 4 U in 24 hours or 6 U in 48 hours
Pelvic fracture and a large or expanding hematoma identified during celiotomy
CT evidence of large retroperitoneal hematoma with extravasation of contrast
Need for detection and treatment of other injuries during angiography
The presence of contrast extravasation on MDCT has been used as an indication for follow-up pelvic angiography. Although it should not delay angiography that is already indicated for pelvic hemorrhage, CT is helpful in localizing the vessels likely to be bleeding not only in the pelvis, but also from the solid organs and thoracic cavity. Correlations of location of the hematoma and site of vascular injury include obturator space and obturator artery, presacral space and lateral sacral artery, space of Retzius and internal pudendal artery, and buttock and gluteal artery.
Femoral access is the preferred approach; however, catheterization may be difficult because of hypotension, tachycardia, and difficulty in palpating the vessels as the pelvic hematoma expands. Ultrasound or fluoroscopic guidance is very helpful in these situations. A 5 French aortic flush catheter is used for flush abdominopelvic aortography. This is valuable to screen the abdominal viscera and mesentery, to exclude aortoiliac and other retroperitoneal bleeding sources, and as a road map of the pelvic vessels. Selective bilateral internal iliac arteriography is mandatory to exclude bleeding sites since aortography may not identify all bleeding. From one access, both internal iliac arteries are sequentially catheterized and opacified. Then, external iliac arteriography is used to evaluate the external pudendal and external obturator vessels.
It is common to identify multiple areas of extravasation during pelvic angiography. These may be bilateral and may involve multiple vascular beds. Extravasation is often punctate, but can be large and coarse, and the size of such extravasations may not correlate with the degree of blood loss. Vascular occlusions due to transection or dissection with subsequent occlusion can be present, as well. It can be difficult to differentiate between arterial injury due to thrombosis and vasospasm. Failure to treat these occlusions may result in recurrent hemorrhage when vasospasm resolves. Arteriovenous fistulas can occur, but are more common in penetrating trauma.
Because bleeding is usually multifocal and originates from multiple small blood vessels, embolization requires small particulate embolization. Large coil occlusion is as ineffective as surgical ligation of the internal iliac artery because bleeding soon resumes through numerous collateral circuits. Surgical gelatin pledgets are ideal because they are inexpensive, readily available, and often temporary lasting only a few weeks and allowing reestablishment of normal blood flow after the tissue has healed (Fig. 15-48A and B). Permanent particulate emboli, however, are often used because of their ease of use through a microcatheter (Fig. 15-49A and B). Embolization is technically successful in more than 90% of patients, and hemorrhage control is highly effective. Survival depends on many other factors including associated injuries, the presence of an open fracture, transfusion requirements, and delays to embolization.
(A and B) Multiple bleeds from pelvic fractures: 48-year-old male driver in a motor crash sustained pelvic fractures requiring transfusions. (A) Circles surround multiple bleeding sites from the region of the sacroiliac joint; from the pelvic side wall on the right hemipelvis emanate anterior and posterior branches of the right internal iliac artery and in the region (B) multiple points of extravasation were detected (circle). They are emanating from the left lateral sacral artery. Such diffuse hemorrhage is not amenable to superselective embolization because it would be too time consuming. Pledgets of surgical gelatin, 2–3 mm in size, can occlude these vessels effectively.
(A and B) A 26-year-old motorcyclist sustained unstable pelvic fractures during a crash. He developed expanding perineal and scrotal hematomas requiring red cell transfusion. (A) Left internal iliac arteriogram reveals a source of bleeding from the left internal pudendal artery (curved arrow). The more medial contrast stain (straight arrow) is a normal finding. It represents the blush of the perineal body and root of the ischiocavernosa muscle that is frequently seen on internal iliac arteriography of mails. (B) Because this was focal hemorrhage, selective embolization via 2.8 French catheter placed coaxially through the 5 French catheter was attempted and successfully achieved hemostasis.
Penetrating Pelvic Trauma
Penetrating trauma is an uncommon indication for pelvic angiography, as many patients are hemodynamically unstable or have clear indications for immediate exploratory celiotomy, often due to injury to a large vessel. Because the extraperitoneal space has been exposed by a penetrating wound, intraperitoneal bleeding is likely and direct exploration is warranted. Occasionally, angiography is valuable when operative control cannot be initially accomplished and damage control has been performed. Angiography and embolization prior to unpacking can aid in decreasing blood loss at a reoperation.
Injuries to large vessels require a very different endovascular strategy than small vessels or end organ vessels. When an injury to a noncritical internal iliac artery or branch has been missed at operation, but detected on postoperative angiography, coil occlusion of both the proximal and distal end of the vessel (whenever possible) is the standard treatment.
Catheter Angiography for Peripheral Vascular Injuries
Almost all peripheral vascular injuries can be reached using a 5 French catheter from femoral access provided a long enough catheter is available. Angiography should be done in multiple projections with opaque marking of the entry and exit wounds demonstrating that the entire course of the wounding agent is within the field of view. Iso-osmolar nonionic contrast medium is the optimal agent for visualization. Multiple images in the arterial, capillary, and venous phases are necessary.
Patients with proximity wounds and stable hematomas, diminished pulses, or signs of an arteriovenous fistula may benefit from either CT angiography or catheter angiography. While debatable to some, “proximity” angiography has value in asymptomatic patients with penetration that has passed close to the estimated path of major vessels. Vascular injuries occur in 3–8% of asymptomatic patients. Failure to diagnose arterial injuries may result in delayed hemorrhage or chronic arteriovenous fistulas with claudication, venous insufficiency, and congestive heart failure. Exclusion angiography avoids the time and effort needed to keep track of patients who may be lost to follow-up.
Vascular injuries resulting from fractures and dislocations are uncommon. Clinical evaluation is often difficult as the hematoma from a fracture may be quite large and indistinguishable from one associated with a vascular injury. Crush wounds, angulation deformities, and fracture hematomas may cause a pulse deficit by kinking, entrapping the vessel, or inducing spasm without an intrinsic vascular injury. A laceration into muscle may result in external blood loss without major vascular injury. Finally, a compartment syndrome may result in tissue ischemia without loss of pulses.
The natural history of many injuries cannot be predicted by the angiographic appearance alone. Therefore, observation of some injuries is warranted. Equivocal findings such as luminal narrowing can be assessed by repeating angiography after infusion of an intra-arterial vasodilator, on a subsequent day. Small irregularities and intimal tears that do not restrict flow may be treated by antiplatelet therapy and will heal (Fig. 15-50A–D).
“Minimal injury” of the popliteal artery. Pedestrian who was struck by a motor vehicle sustained comminuted tibial plateau fracture of the left knee. Pulses were diminished and angiography was sought after incomplete reduction. (A and B) Initial popliteal arteriogram showed numerous filling defects consistent with intimal tears (white arrows). Patient was treated with aspirin. (C and D) Arteriogram 1 week later showed healing of the intimal tears.
Treatment of angiographically diagnosed vascular injuries is based on the criticality of the bleeding vessel, its size, location, and accessibility, the hemodynamic condition of the patient, and the type of lesion. Small vessels that are not essential for tissue perfusion can be treated by small particle embolization, using surgical gelatin pledgets or more permanent smaller agents. Permanent agents have no advantage, but in some instances are more easily administered through microcatheters than surgical gelatin. These agents are delivered by flow direction toward the path of least resistance, which is usually toward the bleeding site. Microcoils can be utilized for injury to a small vessel provided they can be delivered near enough to the injury site to avoid collateral recruitment that permits continued bleeding. Examples of vessels that can be treated by embolization of small particles include hemorrhage from a pelvic fracture, multifocal hepatic arterial hemorrhage, and injuries to muscular branches such as those of the profunda femoris artery in the lower extremity.
Injury to larger vessels such as those greater than 3 mm in diameter requires two techniques, one for essential vessels and one for expendable vessels. The treatment of essential vessels requires repair of the bleeding site while allowing continued blood flow. Thus, stent grafts can be deployed to cover the injured segment while allowing antegrade flow (Fig. 15-51).
Thrombosis of popliteal artery with endovascular repair. A 46-year-old morbidly obese woman sustained comminuted tibial plateau fractures after a fall from curb. Pulses were absent. (A) Popliteal arteriogram shows complete occlusion of the mid-popliteal artery. (B) The catheter was quickly advanced to a location just above the occlusion and a guidewire advanced easily into the posterior tibial artery. An ePTFE reinforced stent graft was deployed between proximal and distal extent of the occlusion. (C) Follow-up popliteal arteriogram showed restoration of direct line flow. The entire procedure took less than 1.5 hours.
Nonessential conduits, such as branches of the profunda femoris artery or the brachial artery, or one of the arteries in the shank, can be safely embolized. Particulate embolization will flow past the injury and penetrate deep into the vascular bed. When conduits are injured, this insult to the vascular bed is unnecessary. Therefore, large vessel agents are used to occlude the damaged segment of the conduit while the vascular bed is perfused through collaterals (Fig. 15-52).
Example of vascular isolation by proximal and distal coil occlusion. A 22-year-old male sustained a single stab wound of the upper left chest resulting in very large hemothorax. (A) Subclavian arteriogram shows that there is active arterial hemorrhage from a lacerated fourth anterior intercostal branch of the left internal mammary artery. (B) Because there was continuity between anterior and posterior intercostals, it was necessary to advance a 2.8 French microcatheter across the laceration into the distal segment to deliver a coil distally before withdrawing the catheter and delivering a coil proximally.
Coils in various sizes, some containing threads or fibers to accelerate thrombosis, are the most common devices used to occlude a large vessel. A coil is sized to have a diameter large enough to prevent distal migration, but not too large to end up recoiling into a parent, nontarget vessel.
The technique of arterial isolation attempts to occlude both the proximal and distal vessels around the area of injury by coiling (Fig. 15-52). The goal is to exclude the vascular defect and prevent rebleeding through collateral vessels. This is highly desirable in most circumstances, but mandatory when treating arteriovenous fistulas. The guidewire is carefully maneuvered distal to the injured segment, but proximal to any branches, and coils are delivered. The catheter is then withdrawn, and coils are placed in the proximal segment.