DOI:10.2214/AJR.08.2011
AJR 2009; 193:W49-W57
© American Roentgen Ray Society
CT Angiography Signs of Lower Extremity Vascular Trauma
Mandip S. Gakhal1 and
Kamyar A. Sartip1
1 Department of Radiology, Christiana Hospital and Christiana Care Health
System, 4755 Ogletown Stanton Rd., Newark, DE 19718.
Received October 23, 2008;
accepted after revision December 31, 2008.
Address correspondence to K. A. Sartip
(ksartip{at}christianacare.org).
CME This article is available for CME credit. See
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for more information.
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Abstract
OBJECTIVE. Specific CT angiography (CTA) signs of vascular injury
can be readily detected, and additional information regarding osseous and
soft-tissue injuries can also be routinely obtained. In this article, we
illustrate the important CTA signs of lower extremity vascular injury.
CONCLUSION. CTA is efficient and accurate in the evaluation of
clinically significant lower extremity arterial injuries after trauma.
Keywords: CT • CTA • CT angiography • lower extremity • trauma • vascular trauma
Introduction
The increased availability, short acquisition time, and high
diagnostic accuracy of MDCT have rendered CT angiography (CTA) of the lower
extremities the initial imaging examination of choice in the diagnosis of
vascular injury after trauma. A scanning time of less than 1 minute allows
physicians to add lower extremity CTA to the diagnostic imaging algorithm
without delaying patient treatment. CTA can also yield additional relevant
information regarding osseous and soft-tissue injuries and their relationship
to the injured vessel.
Studies comparing CTA of the extremities with conventional angiography have
shown CTA to be comparable in accuracy, more time-efficient, less invasive,
and less expensive in diagnosing traumatic arterial injuries
[1,
2]. Analysis of 62 arterial
lesions in 55 of 87 patients with trauma to the upper or lower extremities by
Rieger et al. [3] using a
4-MDCT scanner yielded retrospective CTA sensitivity and specificity of 99%
and 87%, respectively. In a study by Inaba et al.
[4], MDCT angiography was
diagnostic in 62 of 63 scans, with 22 positive studies in 59 patients with
lower extremity trauma; and CTA achieved sensitivity and specificity of 100%
for detecting clinically significant arterial injury. In a study evaluating
137 arterial injuries in the proximal extremities of 134 patients, Soto et al.
[5] determined single-detector
helical CTA to have a diagnostic sensitivity of 95.1% and specificity of
98.7%. CTA has been successfully used for more specialized applications in
recent studies, such as evaluation of the distal lower extremity arteries in
patients with high-energy tibial plafond fractures before orthopedic
intervention [6] and in
pediatric patients with extremity injury before reconstructive surgery
[2].
Vascular Injury
Clinical findings of vascular injury from penetrating or blunt trauma as
described by Compton and Rhee
[7] can be categorized into
hard and soft signs. Hard signs include absent or diminished pulses, active
hemorrhage, large expanding or pulsatile hematoma, bruit, thrill, or distal
ischemia. Soft signs include a small stable hematoma, injury to an
anatomically related nerve, unexplained hypotension, and proximity of an
injury to a major vessel [7]. A
recent publication showed effective performance of CTA in patients presenting
with soft signs of vascular injury and an ankle-brachial index of less than
0.9, with no false-negatives and no missed injuries
[8]. Patients presenting with
hard signs could potentially proceed directly to operative management.
However, it is desirable to perform CTA in all patients who are sufficiently
stable to undergo the examination because it can be rapidly performed,
decreases diagnostic ambiguity, provides valuable information to the vascular
surgeon or interventionalist, avoids unnecessary intraoperative exploration,
and decreases procedure time. The IV contrast agent administered for CTA
usually does not hinder additional use should it become necessary to perform
conventional arteriography. In our experience, CTA of the lower extremities is
being increasingly performed for the entire spectrum of vascular injuries and
in combination with CT of other body parts, particularly in patients with
complex multitrauma.
CTA Technique
The ability to consistently obtain high-quality CTA studies requires the
proper technique and attention to details. Suitable access for contrast
injection, such as a peripheral IV line greater than 20-gauge and preferably
in the antecubital fossa, or a central venous catheter that has been approved
by the manufacturer for power injection, should be used. CTA protocols vary
depending on the type of scanner, manufacturer, and institutional preferences;
a comprehensive discussion of all the possible scanning parameter permutations
is beyond the scope of this article. In general, we recommend working with
your scanner manufacturer applications specialist, reviewing the literature,
and contacting established sites with equipment similar to yours as starting
points, with subsequent protocol modification and optimization based on your
own experience.
Our current routine 64-MDCT protocol parameters for lower extremity CTA
trauma studies include 120 kVp, 200-300 mAs, collimation of 64 x 0.6 mm,
gantry rotation speed of 0.37 second, pitch of 0.65, slice thickness of 0.75-2
mm with a reconstruction interval of 0.5-1 mm, and a B31 medium smooth
reconstruction kernel. One hundred milliliters of iodinated IV contrast
material is usually injected at a rate of 3 mL/s, followed by a saline flush.
We use contrast bolus tracking and a trigger threshold of 100 HU, with the
region of interest placed in the upper abdominal aorta if the abdomen and
pelvis are also included. The protocol can be modified for a specific site of
injury. For example, if injury is limited to the calf vessels, the region of
interest for the bolus trigger could be placed in the popliteal artery, with
scanning coverage limited to that level. We do not routinely obtain
unenhanced, venous, or delayed phase images in all patients, but do so in a
selective manner.
The images are monitored by the technologist as they are generated, and if
no contrast material is seen in the vessels, a repeat scan is triggered.
Alternatively, in patients with known poor cardiac output, severe
atherosclerotic disease, severe osseous or soft-tissue injury, and other
situations in which significant reduction in contrast transit is likely, a
second acquisition with more limited anatomic coverage could be empirically
performed. In addition, introducing a more prolonged scanning delay,
increasing the injection rate and duration, biphasic injection, reducing table
speed, and choosing contrast material with a higher iodine concentration can
improve image quality. Positioning the vascular structures of interest as
close as possible to the isocenter of the CT gantry can aid in achieving
maximal image fidelity [9].
Image quality issues also arise when dealing with trauma patients who have
metallic foreign bodies or hardware such as external fixators. In those
instances, the decision to proceed with CTA demands individualized
evaluation.
CTA Image Analysis
The methods of CTA image interpretation vary among individuals, but a
systematic and comprehensive approach is necessary regardless of the details.
Diagnosis of vascular injuries relies heavily on careful analysis of the axial
source images and interactive review of 2D multiplanar reformations (MPRs).
Dynamic adjustment of window and level settings as needed by the interpreter,
rather than using only fixed values, is often necessary to adequately
discriminate between contrast material, calcification, noncalcified plaque,
thrombus, a dissection flap, and other vessel wall or lumen components. For
example, using wide window and level settings (window width and level of 1,200
and 20 HU) can aid evaluation of the lumen adjacent to calcified plaque by
reducing blooming artifact [9].
Additional beneficial postprocessing techniques that are used in concert
include curved planar reformations, maximum-intensity-projection (MIP) images,
and 3D volume-rendered images. These latter techniques are useful for summary
display of the important findings in an easy-to-understand and attractive
format, particularly from the standpoint of the surgeons. Often, it is not
necessary to engage in tedious manipulations to exclude all the nonvascular
structures from the 3D images, particularly if there are accompanying
fractures. Even with isolated vascular injury, it is important to preserve
visibility of some background structures so they may serve as anatomic
landmarks for surgical planning (Fig.
1A, and
1B).
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Fig. 1A —38-year-old man involved in collision while riding motorcycle
who presented with extensive soft-tissue and partial degloving injury, as well
as fractures of left leg. Volume-rendered CT angiography (CTA) images show
comminuted fractures of tibia and fibula and lack of opacification of
tibioperoneal trunk (between arrowheads, A) and proximal 3.5
cm of peroneal artery (between arrows, A). No vascular
intervention was performed on basis of clinical decision to instead address
more extensive soft-tissue and orthopedic injuries. However, CTA provided
orthopedic surgeon necessary information required for surgical planning of
open reduction and internal fixation of tibial and fibular fractures.
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Fig. 1B —38-year-old man involved in collision while riding motorcycle
who presented with extensive soft-tissue and partial degloving injury, as well
as fractures of left leg. Volume-rendered CT angiography (CTA) images show
comminuted fractures of tibia and fibula and lack of opacification of
tibioperoneal trunk (between arrowheads, A) and proximal 3.5
cm of peroneal artery (between arrows, A). No vascular
intervention was performed on basis of clinical decision to instead address
more extensive soft-tissue and orthopedic injuries. However, CTA provided
orthopedic surgeon necessary information required for surgical planning of
open reduction and internal fixation of tibial and fibular fractures.
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CTA Signs of Lower Extremity Vascular Injury
CTA signs of vascular injury in lower extremity trauma include active
contrast extravasation, an extravascular contrast material-containing
collection, loss of opacification or occlusion of an arterial segment, abrupt
vessel narrowing, intraluminal filling defect, early venous opacification, and
abnormal change in vessel caliber, contour, or course
[10-12].
Active extravasation of contrast-enhanced blood, indicative of ongoing
hemorrhage, manifests as an irregular blush of extraluminal contrast material
near the focal arterial mural disruption that may insinuate into adjacent soft
tissues and muscles (Figs. 2A,
2B and
3). A more organized
extravascular contrast-filled sac connected to a vessel through a neck at a
site of focal arterial wall discontinuity is indicative of pseudoaneurysm
formation [13] (Figs.
4A,
4B,
5A,
5B,
6A,
6B, and
6C). Hematoma around a focus
of active contrast extravasation or a perfused pseudoaneurysm sac can vary
considerably in size.
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Fig. 2A —18-year-old man with through-and-through gunshot injury to
left thigh, minimally palpable popliteal artery, and barely discernible
Doppler signal in posterior tibial and dorsalis pedis arteries. Oblique
volume-rendered CT angiogram shows segmental narrowing of lumen of left
superficial femoral artery (arrow).
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Fig. 2B —18-year-old man with through-and-through gunshot injury to
left thigh, minimally palpable popliteal artery, and barely discernible
Doppler signal in posterior tibial and dorsalis pedis arteries. Sagittal
maximum-intensity-projection CT angiogram reveals active contrast
extravasation (large arrow) from posterior aspect of superficial
femoral artery near upper margin of lumen narrowing (arrowhead).
Small bullet fragments are also noted (small arrows). Small hole in
superficial femoral artery wall measuring approximately 1 mm was discovered at
surgery and repaired primarily with sutures. Complete transection of adjacent
femoral vein was also found, with 2.5-cm-long defect that was repaired with
saphenous vein interposition graft.
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Fig. 3 —15-year-old boy with gunshot injury to right thigh. At
presentation, right popliteal, posterior tibial, and dorsalis pedis pulses
were not palpable, and there were no Doppler signals. Volume-rendered CT
angiogram at level of lower thigh shows segmental narrowing
(arrowheads) of superficial femoral artery and adjacent active
contrast extravasation (arrow). Surgical exploration found focal
disruption of posterolateral aspect of superficial femoral artery just above
adductor canal, spanning approximately 30% of vessel circumference and
measuring 1.5 cm in length. Small focal intimal injury at opposite side of
vessel was also noted. Arterial débridement, primary repair with
sutures, saphenous vein patch, and thrombectomy were required. Large
disruption of adjacent femoral vein was also surgically repaired, and
four-compartment lower leg fasciotomies and thigh fasciotomy were performed
because of high risk for compartment syndrome.
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Fig. 4A —28-year-old man with self-inflicted stab wound to right lower
leg with pain and bleeding but intact pulses. Volume-rendered (A) and
maximum-intensity-projection (B) CT angiograms show small
pseudoaneurysm (arrow) arising from proximal anterior tibial artery.
Subsequent conventional arteriogram confirmed pseudoaneurysm but also revealed
arteriovenous fistula to anterior tibial vein. Endovascular repair was
performed with placement of 6 x 25 mm covered stent in proximal anterior
tibial artery.
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Fig. 4B —28-year-old man with self-inflicted stab wound to right lower
leg with pain and bleeding but intact pulses. Volume-rendered (A) and
maximum-intensity-projection (B) CT angiograms show small
pseudoaneurysm (arrow) arising from proximal anterior tibial artery.
Subsequent conventional arteriogram confirmed pseudoaneurysm but also revealed
arteriovenous fistula to anterior tibial vein. Endovascular repair was
performed with placement of 6 x 25 mm covered stent in proximal anterior
tibial artery.
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Fig. 5A —55-year-old man with history of atherosclerotic disease who
presented with foot numbness and coldness 4 days after right iliac angioplasty
and stent placement in left common and external iliac arteries. Both groins
were punctured for vascular access during procedure. Transverse thin
maximum-intensity-projection CT angiogram shows patent (long arrow)
and thrombosed (arrowheads) portions of pseudoaneurysm arising from
proximal superficial femoral artery (short arrow).
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Fig. 5B —55-year-old man with history of atherosclerotic disease who
presented with foot numbness and coldness 4 days after right iliac angioplasty
and stent placement in left common and external iliac arteries. Both groins
were punctured for vascular access during procedure. Sagittal volume-rendered
CT angiogram shows rounded patent portion of pseudoaneurysm (arrow)
connecting via narrow neck to proximal left superficial femoral artery
(arrowhead). Pseudoaneurysm was successfully treated with
sonographically guided thrombin injection.
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Fig. 6A —71-year-old man with history of right femoral
artery-to-below-knee popliteal saphenous vein bypass graft done 30 years
earlier who presented with progressive swelling of right popliteal region 3
months after bilateral knee replacement surgery. CT angiography was performed
to further evaluate abnormal sonogram of popliteal fossa. Posterior
volume-rendered CT angiogram shows bilateral knee prostheses
(arrowheads). Femoral-popliteal graft (arrow) is faintly
visible on this image.
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Fig. 6B —71-year-old man with history of right femoral
artery-to-below-knee popliteal saphenous vein bypass graft done 30 years
earlier who presented with progressive swelling of right popliteal region 3
months after bilateral knee replacement surgery. CT angiography was performed
to further evaluate abnormal sonogram of popliteal fossa. Coronal (B)
and transverse (C) thin maximum-intensity-projection CT angiograms show
patent (arrowhead) and thrombosed (short arrows) portions of
pseudoaneurysm arising from diffusely dilated and partly calcified vein graft
(long arrow) above knee joint level. Remainder of graft, popliteal
artery, and all vessels below knee were not opacified on CT angiography
because of slow flow. Subsequent conventional arteriogram before surgery
showed atherosclerotic but patent vessels below knee joint. New right femoral
to distal popliteal to anterior tibial sequential saphenous vein graft was
placed with ligation of old graft.
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Fig. 6C —71-year-old man with history of right femoral
artery-to-below-knee popliteal saphenous vein bypass graft done 30 years
earlier who presented with progressive swelling of right popliteal region 3
months after bilateral knee replacement surgery. CT angiography was performed
to further evaluate abnormal sonogram of popliteal fossa. Coronal (B)
and transverse (C) thin maximum-intensity-projection CT angiograms show
patent (arrowhead) and thrombosed (short arrows) portions of
pseudoaneurysm arising from diffusely dilated and partly calcified vein graft
(long arrow) above knee joint level. Remainder of graft, popliteal
artery, and all vessels below knee were not opacified on CT angiography
because of slow flow. Subsequent conventional arteriogram before surgery
showed atherosclerotic but patent vessels below knee joint. New right femoral
to distal popliteal to anterior tibial sequential saphenous vein graft was
placed with ligation of old graft.
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Vessel caliber reduction on CTA can indicate the presence of spasm,
dissection, or external compression. Lumen narrowing with irregular contour
signifies a partial-thickness wall injury and thrombus
[11]. Abnormal caliber change
can be subtle, especially in the distal lower extremities, where the native
lumen normally tapers and the limits of CTA resolution are approached
[10]. Arterial transection and
complete rupture can result in segmental vessel occlusion. Injuries that
result in vessel narrowing can also cause or progress to lack of lumen
opacification and segmental occlusion
[3] (Fig.
7A, and
7B). The occlusion can vary in
length, with reconstitution further distally via collaterals. The collaterals
can be difficult to identify in the setting of acute trauma, unlike
atherosclerosis, in which they are typically larger and more readily visible
because of their much longer temporal evolution and established presence.
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Fig. 7A —39-year-old man who sustained posterior right knee
dislocation during fall from ladder. Patient reported paresthesias in
posterior compartment, and fleeting Doppler signals were present in posterior
tibial artery. Posterior coronal volume-rendered (A) and
maximum-intensity-projection (B) CT angiograms show abrupt segmental
occlusion of right popliteal artery (between arrowheads). Complete
transection of popliteal artery was found at surgery. Repair was performed
with saphenous vein interposition and two-compartment anterolateral
fasciotomy.
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Fig. 7B —39-year-old man who sustained posterior right knee
dislocation during fall from ladder. Patient reported paresthesias in
posterior compartment, and fleeting Doppler signals were present in posterior
tibial artery. Posterior coronal volume-rendered (A) and
maximum-intensity-projection (B) CT angiograms show abrupt segmental
occlusion of right popliteal artery (between arrowheads). Complete
transection of popliteal artery was found at surgery. Repair was performed
with saphenous vein interposition and two-compartment anterolateral
fasciotomy.
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Intraluminal filling defect can represent thrombus or intimal flap, with
the latter appearing linear and denoting the presence of a localized
dissection (Fig. 8A,
8B, and
8C). However, dissection can
also appear as a semilunar lumen deformation, eccentric stenosis, or segmental
thrombotic occlusion [3].
Arterial injury not only can result in thrombus at the site of injury but also
can cause thromboembolism further downstream (Fig.
9A, and
9B).
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Fig. 8A —24-year-old woman with history of bipolar disorder who jumped
from overpass onto interstate highway and sustained fractures to pelvis and
left foot as well as left posterior knee dislocation. Ankle-brachial index was
0.7 on left and normal on right. Volume-rendered CT angiogram shows focal
lumen narrowing of left popliteal artery (arrow).
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Fig. 8B —24-year-old woman with history of bipolar disorder who jumped
from overpass onto interstate highway and sustained fractures to pelvis and
left foot as well as left posterior knee dislocation. Ankle-brachial index was
0.7 on left and normal on right. Coronal (B) and sagittal (C)
curved planar reformations reveal focal lumen narrowing and filling defect in
popliteal artery (arrow). Intimal flap was found in popliteal artery
at site of CT angiography abnormality during surgical exploration and was
repaired with sutures and saphenous vein patch.
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Fig. 8C —24-year-old woman with history of bipolar disorder who jumped
from overpass onto interstate highway and sustained fractures to pelvis and
left foot as well as left posterior knee dislocation. Ankle-brachial index was
0.7 on left and normal on right. Coronal (B) and sagittal (C)
curved planar reformations reveal focal lumen narrowing and filling defect in
popliteal artery (arrow). Intimal flap was found in popliteal artery
at site of CT angiography abnormality during surgical exploration and was
repaired with sutures and saphenous vein patch.
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Fig. 9A —31-year-old man with gunshot wound to left lateral thigh,
cool lower leg, and no palpable distal pulses or Doppler signals. Coronal
(A) and sagittal (B) maximum-intensity-projection CT angiograms
show active contrast extravasation (long arrow) and segmental lack of
opacification of left superficial femoral artery (between short
arrows) at site of gunshot injury. In addition, note segmental lack of
opacification of popliteal artery (between arrowheads) further distal
due to downstream thromboembolism from superiorly located superficial femoral
artery injury, followed by opacification of posterior tibial artery only.
Focal posterior disruption of superficial femoral artery and segmental
thrombosis were confirmed at surgery. In addition to local thrombectomy,
distal thrombectomies were performed with Fogarty catheter; clot was removed,
4-5 cm of injured superficial femoral artery was resected, and synthetic graft
was placed. Notably, approximately 800 mL of venous hemorrhage occurred
intraoperatively once arterial repair was performed and flow re-established,
which was controlled with sutures and packing. This example emphasizes need
for exclusion of tandem arterial abnormalities and imaging of vessels distal
to site of injury; it also raises awareness of possibility of concurrent
venous injury.
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Fig. 9B —31-year-old man with gunshot wound to left lateral thigh,
cool lower leg, and no palpable distal pulses or Doppler signals. Coronal
(A) and sagittal (B) maximum-intensity-projection CT angiograms
show active contrast extravasation (long arrow) and segmental lack of
opacification of left superficial femoral artery (between short
arrows) at site of gunshot injury. In addition, note segmental lack of
opacification of popliteal artery (between arrowheads) further distal
due to downstream thromboembolism from superiorly located superficial femoral
artery injury, followed by opacification of posterior tibial artery only.
Focal posterior disruption of superficial femoral artery and segmental
thrombosis were confirmed at surgery. In addition to local thrombectomy,
distal thrombectomies were performed with Fogarty catheter; clot was removed,
4-5 cm of injured superficial femoral artery was resected, and synthetic graft
was placed. Notably, approximately 800 mL of venous hemorrhage occurred
intraoperatively once arterial repair was performed and flow re-established,
which was controlled with sutures and packing. This example emphasizes need
for exclusion of tandem arterial abnormalities and imaging of vessels distal
to site of injury; it also raises awareness of possibility of concurrent
venous injury.
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Early venous enhancement on properly timed arterial phase CTA should prompt
evaluation for posttraumatic arteriovenous fistula. There can be an
accompanying increase in size or caliber of the veins as well, especially if
the fistula is subacute to chronic (Figs.
10A,
10B,
10C,
10D,
10E,
10F, and
10G). In some instances, the
exact site and nature of communication between the artery and vein are
incompletely defined by CTA and require conventional catheter angiography
[5].
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Fig. 10A —27-year-old man with history of injury from BB gun in left
lower leg who presented with pulsatile swollen leg and numerous enlarged
veins. Transverse CT angiogram reveals enlarged anterior tibial artery
(arrow) and enlarged anterior tibial veins (arrowheads).
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Fig. 10B —27-year-old man with history of injury from BB gun in left
lower leg who presented with pulsatile swollen leg and numerous enlarged
veins. Arteriovenous fistula is shown: direct communication between anterior
tibial artery and vein (arrow). Note adjacent retained BB pellet
(arrowhead).
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Fig. 10C —27-year-old man with history of injury from BB gun in left
lower leg who presented with pulsatile swollen leg and numerous enlarged
veins. Transverse CT angiogram reveals anterior tibial artery (arrow)
to be much smaller distal to level of arteriovenous fistula and dilation of
anterior tibial veins (arrowheads).
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Fig. 10D —27-year-old man with history of injury from BB gun in left
lower leg who presented with pulsatile swollen leg and numerous enlarged
veins. Numerous other dilated veins are shown near ankle (arrowheads)
as result of arteriovenous fistula.
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Fig. 10E —27-year-old man with history of injury from BB gun in left
lower leg who presented with pulsatile swollen leg and numerous enlarged
veins. Volume-rendered CT angiogram shows dilated superficial veins
(arrowheads).
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Fig. 10F —27-year-old man with history of injury from BB gun in left
lower leg who presented with pulsatile swollen leg and numerous enlarged
veins. Volume-rendered CT angiogram with soft tissues removed reveals
extensively dilated veins in left leg (arrowheads). Portion of
dilated anterior tibial artery (arrow) above arteriovenous fistula is
also identifiable.
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Fig. 10G —27-year-old man with history of injury from BB gun in left
lower leg who presented with pulsatile swollen leg and numerous enlarged
veins. Volume-rendered CT angiogram shows arteriovenous fistula between
anterior tibial artery and vein (long arrow) as well as adjacent
retained BB pellet (arrowhead). Some linear striations at site of
fistula are due to streak artifact from BB pellet. Anterior tibial artery is
enlarged above level of arteriovenous fistula and much smaller distal to
fistula (short arrows). Dilated veins are shown alongside anterior
tibial artery and elsewhere. Arteriovenous fistula was confirmed at surgery
and repaired using minimally invasive procedure with CT angiography guiding
surgical approach.
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CTA Pitfalls
Potential pitfalls in CTA interpretation include suboptimal contrast
attenuation in the vessel lumen, incomplete vessel opacification because of
discrepancy between transit of the contrast bolus and timing of the image
acquisition, and vessel underfilling from slow flow as a result of injury
further upstream. Selective use of additional scans, as discussed previously,
particularly from the level of the knees to the toes, may aid in avoiding this
pitfall. Other variables that can confound or hinder accurate interpretation
include vessel spasm, anatomic variants, underlying atherosclerosis, displaced
fracture fragments, artifacts from metal, foreign bodies, and patient motion
or positioning constraints (Fig.
11A,
11B, and
11C).
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Fig. 11A —45-year-old man who was in motorcycle crash and presented
with comminuted fracture of proximal left tibia and fibula, as well as
multiple foot fractures. He underwent external fixator placement followed by
CT angiography because of clinical concern for possible vascular compromise.
Volume-rendered CT angiogram shows diagnostic-quality images despite external
fixator, particularly near fracture planes.
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Fig. 11B —45-year-old man who was in motorcycle crash and presented
with comminuted fracture of proximal left tibia and fibula, as well as
multiple foot fractures. He underwent external fixator placement followed by
CT angiography because of clinical concern for possible vascular compromise.
Volume-rendered CT angiograms with bones in background (B) and bones
removed (C) show normal anterior tibial artery (long arrow),
small-caliber posterior tibial artery (arrowhead), and enlarged
peroneal artery (short arrow) based on developmental normal anatomic
variant rather than vascular injury.
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Fig. 11C —45-year-old man who was in motorcycle crash and presented
with comminuted fracture of proximal left tibia and fibula, as well as
multiple foot fractures. He underwent external fixator placement followed by
CT angiography because of clinical concern for possible vascular compromise.
Volume-rendered CT angiograms with bones in background (B) and bones
removed (C) show normal anterior tibial artery (long arrow),
small-caliber posterior tibial artery (arrowhead), and enlarged
peroneal artery (short arrow) based on developmental normal anatomic
variant rather than vascular injury.
|
|
Blooming artifact from calcified plaque that may obscure the vessel lumen
and result in stenosis overestimation can be minimized by reducing partial
volume averaging, selecting the thinnest possible slice thickness for
reconstructing the initial transverse images, and using wide window and level
settings. During image acquisition, metal artifacts can be reduced by using
higher peak voltage and tube current settings, as well as decreased
collimation and pitch values. During image reconstruction, the use of thick
sections, lower kernel values, and extended CT scale can reduce metal
artifacts [14]. Patient motion
artifacts can be averted by taping the knees together or other similar
restraint. Primary venous abnormalities and infection should be excluded as
potential causes for dilated veins or asymmetric avid venous enhancement in
the lower extremities before attributing their presence to an arteriovenous
fistula. Notably, venous injury adjacent to an abnormal artery is occult on
CTA when only arterial phase images are obtained, so venous injuries are often
discovered at the time of surgical exploration.
Summary
CTA is efficient and accurate in the evaluation of lower extremity arterial
injuries after trauma. Specific CTA signs of vascular injury can be readily
detected, and additional information regarding osseous and soft-tissue
injuries can also be routinely obtained.
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Abstract
Introduction
