Ultrasound Case of the Month - July 2019

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THE CASE…

A woman in her mid 70s with a past medical history of coronary artery disease, atrial fibrillation on anticoagulation, hypertension, and hyperlipidemia who presents to the emergency department (ED) with left leg pain for the past two weeks. She describes the pain as fairly severe, located in the mid posterior calf, without significant radiation. The pain is not accompanied by sensory changes. She denies fever, chest pain, dyspnea, and cough. She denies any traumatic precipitant. She denies missing any doses of her anticoagulation lately. The patient’s primary care provider was concerned about possible deep vein thrombosis (DVT) and referred her to the ED. Of note, she received a course of oral levofloxacin two weeks prior to this presentation for community-acquired pneumonia.

The temperature is 37 C, HR 76 bpm, BP 127/70 mmHg, respiratory rate 16 per minute, pulse oximetry 97% on room air. There is normal passive range of motion in the left knee and ankle. Dorsalis pedis and posterior tibialis pulses are full with a normal capillary refill time in both feet. Compartments are soft. There is mild fullness in the distal left calf, over the Achilles tendon, which is quite tender to palpation. There is no overlying erythema or induration.

A point of care ultrasound was performed of the left lower extremity, with special focus to the area of maximal tenderness...

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What Do You See on Ultrasound?

There are two images provided, one in the transverse plane and one in the longitudinal plane, of the left Achilles tendon. There is an abnormal echotexture in the tendon with some surrounding anechoic layering that is consistent with fluid. These findings are most consistent with underlying tendinopathy, or, in the context of recent fluoroquinolone use, partial Achilles tendon tear.

Musculoskeletal Ultrasound Pearls

Achilles tendon injuries are a notable source of morbidity in both the athletic and sedentary – with rupture incidence cited between 5-10 cases per 100,0002. These injuries tend to occur more commonly in competitive athletes and are often the result of dramatic dorsiflexion of a plantar flexed extremity, or a strong force exerted through an ankle paired with an extended knee3. Achilles tendinopathy, while less dramatic than a frank rupture, is a much more common source of acute ankle pain, frequently occurring in patients who have an abrupt increase in physical activity.

The clinical examination of acute musculoskeletal injuries in the ED can often be limited by the amount of tenderness experienced by the patient. Further, edema surrounding the injury locale can cloud an accurate assessment. While the Thompson test, a brisk squeeze of the gastrocnemius producing appropriate plantarflexion at the ankle, has impressive test characteristics (sensitivity 96%, specificity 93% for complete Achilles tendon rupture), patient discomfort can complicate an accurate assessment4. It should also be noted that compensatory plantar flexion can be accomplished by adjacent muscles, primarily the peroneal and posterior tibialis – thus the ability to actively plantarflex does not rule out tendon injury.

POCUS can overcome the issues of patient participation and pain, and serve as a ready adjunct to physical exam in the ED. Imaging of the Achilles tendon is accomplished by placing the patient in the prone position on a gurney, with his or her feet hanging over the edge1. A high frequency probe is preferred due to the superficial location of the tendon. Scanning is performed in both the transverse and axial planes along the full length of the tendon sheath, taking care to include the area of maximal tenderness. Comparison to the unaffected side is essential. A normal tendon (see Figure 1 below) has a characteristic echotexture, often described as parallel layering of hyperechoic fibers5. Loss of this typical appearance can be seen with disruption of the tendon or secondary to anisotropy, a commonly encountered imaging artifact. Anisotropy results from a change in the angle of reflected ultrasound beams. As an object’s surface deviates from a plane initially parallel to the ultrasound receiver, the image can lose defining echotexture, as the reflected ultrasound beams strike the receiver at increasingly non-perpendicular angles (see Radiopaedia for an excellent discussion of anisotropy)5. It is particularly key for examiners to be aware of probe position when examining tendons, as anisotropy can create hypo- or anechoic areas that mimic partial tears or edema, leading to false positive interpretations.

Tendinopathy can produce a number of abnormalities on ultrasound. Complete tears may be quite dramatic, showing up as a tangled web of connective tissue fibers divided by a swath of anechoic fluid. These can be assessed dynamically by gentle plantar flexion of the affected ankle - an increasing gap between the tendon ends is suggestive of complete disruption. Activation of the gastric while imaging a partial tear should not pull the questioned ends apart, they should glide together3. Some of the more predictive signs of full disruption of the tendon include tendon retraction with posterior acoustic shadowing, as well as absence of tendon tissue at the site in question6. Partial thickness tears can be difficult to differentiate from long-standing tendinopathy due to similar sonographic manifestations: thickening of the tendon sheath and discrete hypoechoic areas in the tendon body. Although ultrasound has demonstrated the ability to distinguish normal tendon from total rupture in adequately trained hands, partial ruptures are best definitively diagnosed by MRI 7.

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Figure 1. Ultrasound exam of a normal Achilles tendon in the axial (left) and longitudinal (right) plane.

Fluoroquinolones

Over the last decade, fluoroquinolones have come under fire for a number of unnerving adverse effects, including the classic association with tendinopathy. The tie between tendinopathy and fluoroquinolone use was first described in a case report in 19838. Since that time, a number of case series have been published solidifying the connection. A series of 42 patients in the Netherlands suggested a significant effect modification by increasing age, especially over 65, and simultaneous systemic steroid administration9. Most frequently tendinopathy occurs within 1 week of starting the antibiotic. The relative risk of morbidity attributable to fluoroquinolone administration alone is difficult to determine. A large scale case control trial in Italy, including >20,000 cases and 100,000 controls, estimated the odds ratio of any tendinopathy to be approximately 1.7 (95% CI 1.4 – 2.0) and Achilles tendon rupture, specifically, to be an alarming 4.1 (95% CI 1.8 – 9.6)10.

Case Resolution

The patient’s ultrasound was read by the attending physician as concerning for partial Achilles tendon tear versus tendinopathy. She was placed in a walking boot and rapid follow up with orthopedics was arranged. Initially she was treated conservatively with prolonged boot placement and physical therapy. Due to a lack of symptomatic improvement over several weeks an MRI was obtained that demonstrated tendinosis with a low-grade interstitial tear of the Achilles tendon, accompanied by associated peritendinous inflammation. She continues to improve and has transitioned from a walking boot to a laced ankle brace.

Take Home Points

  • Bedside ultrasound has acceptable test characteristics for identifying complete tears of the Achilles tendon in acute presentations in trained hands.
  • Scanning should start in the area of maximal tenderness in cases of musculoskeletal ultrasound.
  • It is unclear how POCUS compares to physical exam alone in diagnosis of Achilles tendon injury in the acute period. Use US as an adjunct to, not replacement for, detailed physical exam.
  • Fluoroquinolones are associated with tendinopathy – this association is enhanced by increasing age, especially over the age of 60, and concomitant use of systemic steroids.

Authored by by Chris Shaw, MD

Dr. Shaw is a PGY-3 in Emergency Medicine at the University of Cincinnati and leads TtS’s US of the Month

Faculty Review by Patrick Minges, MD

Dr. Minges is an Assistant Professor of Emergency Medicine at the University of Cincinnati and is fellowship trained in Ultrasound.

References

  1. Dong, Q., & Fessell, D. P. (2009). Achilles tendon ultrasound technique. American journal of roentgenology, 193(3), W173-W173.

  2.   Leppilahti, J., Puranen, J., & Orava, S. (1996). Incidence of Achilles tendon rupture. Acta Orthopaedica Scandinavica, 67(3), 277-279.

  3. Adhikari, S., Marx, J., & Crum, T. (2012). Point-of-care ultrasound diagnosis of acute Achilles tendon rupture in the ED. The American journal of emergency medicine, 30(4), 634-e3.

  4. Maffulli, N. (1998). The clinical diagnosis of subcutaneous tear of the Achilles tendon. The American journal of sports medicine, 26(2), 266-270.

  5. Bleakney, R. R., White, L. M., & Maffulli, N. (2005). Imaging of the Achilles tendon. Foot Ankle Clin, 10(2), 239-254.

  6. Hartgerink, P., Fessell, D. P., Jacobson, J. A., & van Holsbeeck, M. T. (2001). Full-versus partial-thickness Achilles tendon tears: sonographic accuracy and characterization in 26 cases with surgical correlation. Radiology, 220(2), 406-412.

  7. Kayser, R., Mahlfeld, K., & Heyde, C. E. (2005). Partial rupture of the proximal Achilles tendon: a differential diagnostic problem in ultrasound imaging. British journal of sports medicine, 39(11), 838-842.

  8. Bailey RR, Kirk JA, Peddie BA. Norfloxacin-induced rheumatic disease [letter]. N Z Med J 1983;96:590.

  9. Van Der Linden, P. D., Van Puijenbroek, E. P., Feenstra, J., In ‘T Veld, B. A., Sturkenboom, M. C., Herings, R. M., ... & Stricker, B. H. C. (2001). Tendon disorders attributed to fluoroquinolones: a study on 42 spontaneous reports in the period 1988 to 1998. Arthritis Care & Research: Official Journal of the American College of Rheumatology, 45(3), 235-239.

  10. Corrao, G., Zambon, A., Bertù, L., Mauri, A., Paleari, V., Rossi, C., & Venegoni, M. (2006). Evidence of tendinitis provoked by fluoroquinolone treatment. Drug safety, 29(10), 889-896.