Ankle-Brachial Index, CT Angiography, and Proximal Tibial Traction for Gunshot Femoral Fracture
Table of Contents
This video demonstrates an algorithm for evaluating suspected vascular injury secondary to penetrating extremity trauma. Descriptions of how to perform an arterial-brachial index (ABI) and arterial-pulse index (API) are reviewed, along with criteria to determine if a computed tomography angiography (CTA) is indicated. Relevant imaging is reviewed with a radiology resident with descriptions of how to systematically assess the scans for injury. The technique for a tibial traction pin, a temporizing measure for long bone fractures, is described.
Penetrating extremity trauma (from ballistic injuries and stab wounds) is a common injury pattern seen in urban trauma centers. It is imperative for medical professionals to understand the algorithm for evaluating vascular injury in these patients.
The patient discussed in this case is a 42-year-old man with no significant past medical history who sustained a gunshot wound to his left lower extremity. He was transferred by emergency medical services from the field to the emergency department where he was evaluated by the trauma surgery service. His primary survey was intact upon arrival. After life-threatening injuries were ruled out with the primary exam, a more detailed “secondary” physical exam was conducted.
A thorough physical exam demonstrated two lacerations, presumed to be from the ballistic injury to the medial and lateral left thigh. There was an obvious deformity, swelling, and associated pain of the proximal left lower extremity. The compartments of the patient’s thigh were appropriately swollen but soft. Pulses of the dorsalis pedis and posterior tibial arteries were palpable.
Plain film imaging of the left lower extremity demonstrated a spiral fracture of the left femur. There was a drill-type fracture of the distal femur. A subsequent computed tomography angiography (CTA) re-demonstrated the spiral femur fracture and noted adequate distal vascular runoff.
Penetrating trauma, such as a ballistic injury, poses threat to osseous and neurovascular structures. Upon arrival, patients are ultimately triaged by means of physical examination and non-invasive modalities. All patients who arrive with a penetrating injury have their vaccination status assessed and are provided with the tetanus vaccine if they are not up to date on their vaccination. In this particular patient, lower extremity vascular status was initially assessed upon secondary survey with palpation of the dorsalis pedis and posterior tibial pulses. An arterial-brachial index (ABI) and arterial-pulse index (API) were utilized to further assess the adequacy of limb perfusion. The API, which evaluates the relative perfusion of the injured and non-injured extremity, was obtained and noted to be 0.87. A CTA was subsequently completed given the API less than 0.9. Re-demonstration of the spiral femur fracture was noted on CT. There was no evidence of contrast extravasation, pooling, vasospasm, or pseudoaneurysm on imaging suggesting adequate distal runoff. After ruling out vascular injury, the orthopaedic surgery team was consulted for further care. Diaphyseal femur fractures are prone to shortening of the distal fracture fragment due to spasm of the surrounding musculature. To temporize the fracture and offer pain control, a proximal tibial traction pin was applied.
The orthopaedic surgery team temporized the femur fracture with skeletal traction. This traction may be performed either in the distal femur or proximal tibia. Given the distal extension of the femur fracture and after confirming a ligamentous stable knee, proximal tibial traction was applied. This procedure was again completed for analgesia. The patient was later taken to the operating room for intramedullary fixation following adequate resuscitation.
This patient presented with a single ballistic injury to his left lower extremity. The incidence of vascular injury secondary to penetrating trauma has been variably reported in the literature. For the lower extremities, the incidence ranges from 3 to 25%, and injury most commonly occurs to the femoral or popliteal vessels.1–3 While his peripheral pulses were palpable, penetrating injuries should be further evaluated by validated, non-invasive measures. His API was less than 0.9, and therefore, a CTA was completed per our institutional and consensus algorithm. Fortunately, there was no evidence of vascular injury on further imaging. The orthopedic surgery service was consulted and a proximal tibial traction pin was placed prior to operative intervention.
The ABI and API are validated, non-invasive means for evaluating subtle vascular injuries that do not have any “hard signs” of vascular injury. These hard signs include pulseless extremity, expanding hematoma, pulsatile bleeding, or signs of a pseudoaneurysm including a palpable thrill and audible bruit. Any patient that has one of these “hard signs” in the setting of any kind of trauma should be taken to the operating room for urgent exploration.1, 4
In the absence of a hard sign of vascular injury but with a penetrating injury mechanism concerning vascular pathology, an ABI or API should be ascertained. As shown in the video, an ABI is evaluated by placing the sphygmomanometer on a patient’s calf and assessing the systolic blood pressure at the level of the dorsalis pedis or posterior tibial artery. This is then compared to the systolic blood pressure from the ipsilateral brachial artery. Two commonly used, though non-validated, ways to quickly estimate an ABI are to use the systolic blood pressure from the automated blood pressure cuff or to use the radial artery (as demonstrated in the video) as a proxy for the brachial artery pressure. While these can help provide an idea of what an ABI would be, they are not adequate replacements for a true ABI. If the patient does not have an ipsilateral extremity from a devastating blast injury or prior amputation, an alternative to the ABI is the API in which the injured limb is compared to the contralateral extremity. The API is measured as a ratio of the pressure at which the pulse (e.g. in our patient the posterior tibial) returns via Doppler relative to that of the contralateral limb.
An ABI less than 0.9 has traditionally been used as a threshold for if a patient should require further testing for vascular injury. At this level, the ABI has a 95% sensitivity and 97% specificity for assessing the clinically-significant vascular injury.1 Guidelines from the two major associations of trauma surgeons (EAST and WEST) agree that patients with an ABI greater than 0.9 can be safely discharged home if no other concern for injury is present as it has been shown that only 5.5% of these patients will return with complications nearly all of which will be wound complications.1, 4, 5 More recent work suggests that for penetrating trauma to the extremities this may still be too high of a threshold and that clinically significant vascular injury is not seen with an ABI >0.7.6
Historically, all patients with concern for vascular injury would require on table angiography to evaluate the vessels of the lower extremity.1 This is a procedure by which a catheter would be placed in the femoral artery of the contralateral lower extremity advanced proximally to the aortic bifurcation and contrast would be evaluated as it was directed down into the vessels of the lower extremity. With the advent of computed tomography angiography, this invasive procedure has been replaced with non-invasive imaging while maintaining 100% specificity and sensitivity for vascular injury and significantly reducing cost for both patients and the hospital.1
Interestingly, when reviewing the mechanism of the spiral fracture seen on the patient’s X-ray and CT, the bullet was not likely the source of the fracture. Ballistic fracture patterns are more commonly comminuted or drill type. Upon further history, the patient noted that he fell after being struck by the bullet. A twisting mechanism, while falling, could explain this spiral fracture pattern. Given the lack of retained projectile and two wounds on the medial and lateral aspect of his thigh, this patient sustained a through-and-through ballistic injury.
In this case, the patient proceeded to the operating room the next morning where he underwent open reduction with internal fixation. He was evaluated by physical therapy the following day and was able to be discharged home with instructions to follow up as an outpatient and work with outpatient physical therapy on the second day of his hospital stay.
No special equipment was used during this case.
Nothing to disclose.
The patient referred to in this video article has given their informed consent to be filmed and is aware that information and images will be published online.
The authors received no funding for this work.
- Fox N, Rajani RR, Bokhari F, et al. Evaluation and management of penetrating lower extremity arterial trauma: An Eastern Association for the Surgery of Trauma practice management guideline. Journal of Trauma and Acute Care Surgery. 2012;73:S315-S320.
- deSouza IS, Benabbas R, McKee S, et al. Accuracy of Physical Examination, Ankle-Brachial Index, and Ultrasonography in the Diagnosis of Arterial Injury in Patients With Penetrating Extremity Trauma: A Systematic Review and Meta-analysis. Academic Emergency Medicine. 2017;24(8):994-1017.
- Weinberg DS, Scarcella NR, Napora JK, Vallier HA. Can Vascular Injury be Appropriately Assessed With Physical Examination After Knee Dislocation? Clin Orthop Relat Res. 2016;474(6):1453-1458.
- Feliciano DV, Moore FA, Moore EE, et al. Evaluation and Management of Peripheral Vascular Injury. Part 1. Western Trauma Association/Critical Decisions in Trauma: The Journal of Trauma: Injury, Infection, and Critical Care. 2011;70(6):1551-1556.
- Sadjadi J, Cureton EL, Dozier KC, Kwan RO, Victorino GP. Expedited Treatment of Lower Extremity Gunshot Wounds. Journal of the American College of Surgeons. 2009;209(6):740-745.
- Hemingway J, Adjei E, Desikan S, et al. Re-evaluating the safety and effectiveness of the 0.9 ankle-brachial index threshold in penetrating lower extremity trauma. Journal of Vascular Surgery. 2020;72(4):1305-1311.e1.
- Inject Local Anesthetic
- Prepare Traction Pin
- Prep and Drape
- Lateral Incision
- Dissection to Tibia
- Drill Pin Through Tibia
- Medial Incision
- Advance Pin Through Medial Incision
- Traction Bow and Dressings
What we're looking at here is a plain film of a patient's left femur following a single gun shot wound to the left lower extremity. As you can see, with these ballistic injuries, you have high force, and can get pretty large, displaced femur fractures. What we are going to be doing today is going through how to obtain an ABI, which stands for an ankle-brachial index, which is commonly used in these incidents when you have these high force injuries that can cause, not only the mechanical trauma that you see here with the broken bone, but also cause arterial damage and result in arterial insufficiency. So, the ankle-brachial index is a tool that you use to compare the blood pressure in the upper extremity to the lower extremity, and what you should see in a normal human is a ratio of 1.1 or greater, and the ratio that would start to get us worried is when the lower extremity has a systolic blood pressure that is 0.9 or less in its ratio to the blood pressure from the upper extremity.
Because this patient has diminutive dorsalis pedis pulses, we will be using his posterior tibial pulse instead. The way that you do this is you have the blood pressure cuff set up and you want this to be distal to your injury that you're trying to evaluate. So, this is, as you can see by the sort of gauze, distal to where this patient's gunshot wound has been, and we will be evaluating the blood flow distal to the wound. At this point, you're going to go ahead and get your doppler all set up. You're going to get your jelly. Turn the volume up. Then you want to find the strongest pulse that you can because that's going to give you the best ratio when you're comparing. And once you have your doppler in place, making sure not to push too hard so as to occlude the artery, you are going to ask your assistant to go ahead and pump up the sphygmomanometer. And what you're looking for is for that triphasic flow to diminish, and then once it's gone, you slowly release the pressure. And that moment when you first hear the return of the doppler flow, which for this patient was at approximately 108 mmHg, is the systolic blood pressure that we're going to use for this. When we are moving quickly, we can at times use the systolic blood pressure that we have on the screen, which is being measured from the patient's left upper extremity with an automatic cuff; however, a true ankle-brachial index is used, again, with the doppler using the cuff from the left upper extremity and measuring it again in this same manual fashion. The second part of it is going to be your brachial portion of the index. For this, we usually use the radial pulse, and you, once again, find a nice strong pulse in the radial artery, and making sure not to compress it too hard. You again have your partner go ahead and inflate the sphygmomanometer. And you wait for the return of the triphasic flow like you heard just now at approximately 114 mmHg. For this, what you do is once you've done this procedure, you take your ankle portion of the ankle-brachial index, which is going to be, for this case, a systolic blood pressure of 108 and you put it over your brachial, which is a systolic blood pressure of 114. It is at 0.94 by my superiors who are much better at mathematics than I am. However, it is still above our worrisome line, which is gonna be at 0.9, at which point a CTA is traditionally indicated.
So, we're up here now, getting our CTA for our patient, and the reason why we are getting this CTA is that, off camera, we ended up performing an API. The only difference is that instead of it being from ankle-to-brachial, you can do from the same level of limb. For instance, in this, we did ankle-to-ankle, and that index was less than 0.9, and because of this, there is concern for potential vascular injury. And we are evaluating this along with the trajectory as an indication for evaluation with CTA. This is a radiograph of the femur. We see a lot of the ballistic material down here. It looks like there's like an obliquely-oriented, displaced fracture of the midshaft of the femur. Then also down here, more in the distal femur, it looks like a comminuted fracture with multiple, small displaced fracture fragments. And that's pretty much it that I can see in the radiograph. He's got this, you know, old screw affixing his femoral head from who knows what. We also had some X-rays of his tibia and fibula. There's really nothing else that's exciting from that. Those are really the only injuries in the lower leg. Okay. As you guys said, there's a reported history of a possible gunshot wound to his head, but I already looked through this and I didn't - it looks completely normal. I didn't see any injury at all, even the soft tissues. Yeah. Seemed normal, I didn't see any injury. Perfect. No hemorrhage or fractures. Right now I'm bringing up, this is the non-contrast and the arterial phase that we have. We always get those, according to the trauma protocol. But there is no evidence of any injury to his abdomen or pelvis? On physical exam? I'm asking you. There wasn't. No. Like a - no? Okay. As far as we can tell, it was just what's going on with the left lower leg. Yeah, okay. Just, on first glance, it looks very clean. No free fluid or any like injury to the soft tissues that would suggest any injury. So now coming down to the leg. You can see, here's the initial - that larger displaced fracture. Yeah. It looks like there's a few small little fracture fragments there. Kind of the main vessel that's coming down into this area now is the SFA that we'd be worried about. I'm following it right here. And so far it looks intact. You can see right here, it's getting very close to those bone fragments. Down at this level it's probably the popliteal artery at this point, coming down into the knee. There's a lot of soft tissue gas around there. Mm hmm. There's a little stranding around the vessel itself, but I mean it seems like it's intact. I don't see any, like, definite contrast extravasating out of it. So there's, I'd say, very, very little suspicion for injury, but just because there's a little stranding around it… Can't say for certain? Yeah. Maybe keep an eye on it. The rest of the runoff looks pretty good. So let's look at this in… I don't know if the joint is involved. That may be the next question. Here's the delayed though before we get to that. These are the delayed phase. I mean, at this point I don't see any significant joint effusion or any hematoma. There may be a tiny bit of fluid in there, but even that I'm not so sure. I think there is some gas in there though. Okay. In the joint capsule itself? I think so. Yeah? Let me try to look at it in different views. And these are the coronal views, they're just MIPs, so they're kind of - They're not great for seeing air. I don't know, it's close. Those little pockets, those little foci of gas, it's like right at the top of the - joint. Mm hmm. Actually I'm not so sure. I think it might be outside the joint. Okay. Just because this is me coming down, and then - this is the only area that's kind of giving me pause, right here. Mm hmm. I don't know, I kind of think that there is. All right. Yeah. I'll pass it on to orthopedics. Yeah. Yeah, see what they say. Mm hmm. So that's pretty much it. Okay. I didn't see anything else. Perfect, thank you so much. Okay, sure.
I'm one of the orthopedic residents taking care of this patient. In this particular patient, he has sustained a ballistic wound to his distal femur as well as a spiral fracture, likely from a secondary fall to the shaft of the femur itself. As a means for pain control, as well as helping reduce shortening, we often put skeletal traction in place. In this particular case, we are unable to do distal femoral traction due to the concomitant fracture distally, so we're going to proceed with a proximal tibial traction. Landmarks for this include palpation of the tibial tubercle and then 1.5 cm distal, another 1.5 cm lateral. Just general rule of thumb whenever you're doing a percutaneous fixation, you always want to go from an area of known to unknown. If we are doing distal femoral, you would go from medial to lateral because the femoral bundle is on the medial side. In this particular case, we're going to go from lateral to medial because of the common peroneal nerve.
First thing we're going to do is numb up the area with a local anesthetic. You numb up both sides. Might feel a little poke and burn. Whenever you inject - withdraw, make sure you're not within a blood vessel. Make a wheal at the skin. In this case, the bone is relatively close to the subcutaneous region. Go down to bone, you feel periosteum. Numb the periosteum. And then you can numb up as you're pulling out. Then you move to - medial side, do the same thing. Another poke. Again, down to periosteum.
So we'll let that set. Then we prepare for the actual traction pin itself. For this, we'll be inserting a 4 mm Steinmann pin. All right.
So then we'll formally prep out the area before placing down some sterile drapes.
All right. Then you take your 11 blade. Check for sensation. Does it feel numb there? I can feel it a little bit. Pressure or pain? Pressure. All right. Double check your landmark. Small incision.
Then you take a hemostat down to bone.
Again, check your landmark. Tibial tubercle, 1.5 cm down, 1.5 cm. Aiming for your landmark on this side. He's young, so the bone can be strong, but you should hear - a pitch change as you're going through the first cortex, which is happening right there. And then you should hear a second pitch change as you're going for the second cortex. Right there. Almost done. Strong bone. There is is. Now it's through. As you can see, lined up with our anticipated mark on the far side, which is the medial.
Grab your 11 blade again. Palpate. Small incision on either side.
Completing proximal tibial traction. You can even out the sides. Cautions: while there is neurovascular bundles posteriorly, you don't want to cut it too far anterior because you could inadvertently go through a single cortex or clip the tibial tubercle off. But as you can see, we've got good, solid fixation from which we can hang weight to help alleviate pain as well as - prevent shortening of the femur fracture, which can aid with ultimate surgical management of this problem.
So, I will set up the tension bow here, dress the wounds, and then apply the weight. These pin sites can drain, so it's important to one - make as small of an incision as you can, and also, in terms of dressing, placing an occlusive dressing like Xeroform or Adaptic can help minimize that. Followed by some Curlex to bolster up the dressing itself. So aside from adding weight, setting up the traction apparatus, that is a proximal tibial traction pin. Do you feel that pulling? Hell yeah. Kind of like what I was pulling before. Yeah. All right, I'm going to go run upstairs and grab some weights. We'll probably put 20 - 30 pounds.