“Hey, I have a minor problem in room 10. Can I ask you a quick question?” You know when your resident approaches you with this statement that the problem is never “minor” and the question is never one that can be answered quickly.
“The guy in 10 sliced open his hand at work two days ago,” the resident begins, “but didn’t come in for treatment because he didn’t want to lose his job. He tied a rag around his hand and just kept working with it all weekend. Now his hand is completely swollen and he can’t move his fingers. I can’t get a good exam of his hand and the hand surgeon wants me to admit him to the medicine team for IV antibiotics. I think he should go to the OR for an exploration and wash-out but the hand surgeon says I haven’t told him anything that bodes of more than just a superficial wound. What should I do?”
You walk into the patient’s room, and sure enough his hand looks like a two-pound sausage in a one-pound wrapper. It’s clear why your resident was having such a hard time obtaining a good neurovascular exam. The patient doesn’t have a fever, but then again, he’s been taking ibuprofen around-the-clock for pain. The injured hand is also noticeably warmer than the contra-lateral side. The laceration is on his palm just proximal to Zone II (PIP joint to distal palm). Since you too feel hampered with your neurovascular exam, a strong concern remains that the patient may have an underlying flexor tendon injury.
Just as you are about to ask your resident whether or not she’s tried evaluating his hand with ultrasound, she pipes up “I know, I know, try looking at it with ultrasound. I tried, but I couldn’t get a good window.”
Rather than respond with words, you take the patient’s hand and place it in a plastic basin filled with water. You realize that this may actually end up being somewhat of a quick and minor problem for you to solve. Floating the ultrasound probe above the patient’s laceration and using the water in the basin as your acoustic window (top), you obtain beautiful images of the flexor tendons in your patient’s hand (bottom). Do you see anything abnormal?
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Use water immersion to ultrasound tendons
Creating your own acoustic window enhanced your visualization of the superficial tendons and enabled you to see that your patient had sustained a large flexor tendon laceration. There is hypoechoic edema noted around the tendon in the sagittal plane, and you see a dark hypoechoic laceration traversing the fibrillar tendons on a longitudinal view (top). You scan through each tendon in both the axial and sagittal plane to ensure that the hypoechoic areas noted are not secondary to anisotropy (see Tips & Tricks below).
Before you can finish saving the last image onto the machine for Q&A, your resident has already called back the hand surgeon to inform him that he hasn’t gotten off the hook quite so easily this time. As you wheel your handy ultrasound machine out of room 10, you can’t help but marvel at how “quick and minor” most problems can become with the help of bedside ultrasonography.
Tips and Tricks | Evaluating Tendons Using Water Immersion
1. A careful history and physical exam will usually reveal whether tendon injury or disruption has occurred. Remember that normal motion can be seen on physical exam even with a 90% tendon disruption. Testing strength against resistance may help pick up a partial tendon injury that would be missed by range or motion assessment alone
2. Ultrasound can be used to augment clinical findings and help expedite the diagnosis, especially when the physical exam may be limited secondary to pain, swelling, or patient cooperation
3. If the target area is superficial, it is often useful to create your own acoustic window. The usual way to do this is with a stand-off pad. A water filled latex glove, jellied up on both sides will work, but there are other tricks as well.
4. Water immersion of a hand, foot or other body part can enhance visualization of superficial structures. Simply float the ultrasound probe in the water a few centimeters above the target structure. On your ultrasound screen, the acoustic layer of water will appear as a dark, anechoic line in the nearfield. The target structure will appear just farfield to this anechoic line.
5. Scan superficial structures with the 7.5 to 10 MHz linear array transducer.
6. Skeletal muscle will appear hypoechoic with interwoven echogenic striations and hyperechoic fascial planes. Adjacent tendons will appear brightly hyperechoic with visible linear fibers on long-axis scanning.
7. Any hypoechoic or anechoic interruption in the hyperechoic tendon fibers should raise the suspicion of a tendon disruption. Hypoechoic or anechoic areas may represent blood or, in subacute injuries, granulation tissue, where the tendon fibers have torn apart.
8. Subtle tendon damage, without actual tearing of the tendon fibers, may display an increase in the tendon cross-sectional area due to localized edema. Compare the area of interest to adjacent segments.
9. If the ultrasound beam is not aimed directly parallel to the tendon fibers, a false hypoechogenicity artifact may be noted (anisotropy).