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Musculoskeletal Imaging
September 2009

Achilles Tendon Ultrasound Technique

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OBJECTIVE. When imaging the elbow with ultrasound, it is important to follow a routine that includes a checklist of anatomic structures.
CONCLUSION. This video will show ultrasound scanning and anatomy of the elbow divided into four quadrants, beginning anterior, then moving medial, lateral, and posterior.
As the strongest tendon of the human body, the Achilles tendon originates from the soleus and gastrocnemius muscles, and inserts onto the posterior calcaneal tuberosity. The tendon is surrounded by a paratenon rather than a synovial sheath. Sonography is an efficient and accurate way to assess the Achilles tendon. Advantages of sonographic evaluation include cost, widely available equipment, ease of contralateral comparison, and the ability to image during joint motion.

Ultrasound Technique

The ultrasound technique for imaging the Achilles tendon is as follows:
Position: The patient is prone with the foot hanging over the edge of the table. Mild dorsiflexion of the ankle and use of thick transmission gel help optimize imaging.
Transducer: A high-frequency transducer of at least 10 MHz is typically used given the superficial location of the structures.
Longitudinal and transverse evaluation: The Achilles tendon can be easily seen when the transducer is placed in the sagittal plane, longitudinal to the tendon fibers. The transducer is moved proximally from the insertion site at the calcaneal tuberosity to the myotendinous junction. The transducer is turned 90 degrees for evaluation in the transverse plane.
Normal appearance: The Achilles tendon should be uniform in thickness and echogenicity in a longitudinal plane, and has a predominately flat or concave anterior margin in a transverse plane.
Dynamic evaluation: Dynamic imaging is important in evaluation of Achilles tendon tears since hemorrhage, fluid, debris, or scar tissue may fill the gap between torn tendon ends. With passive movement of the foot or by gently squeezing the calf muscles (Thompson test), the gap between the torn tendon ends becomes more obvious as one tendon end moves without translation of movement to the other tendon end.

Achilles Tendon Abnormalities

The main disorders affecting the Achilles include injury and degenerative processes. Tears of the Achilles tendon most commonly occur 2–6 cm proximal to the calcaneal insertion site.
Tendinosis: Tendinosis typically appears as fusiform hypoechoic swelling of the tendon without disruption of the fibers. Hyperemia may be present due to hypervascularity, not secondary to inflammation, hence the term “tendonosis” is used rather than tendinitis.
Partial tear: Achilles tendon enlargement greater than 1 cm in the anterior–posterior dimension or marked intrinsic tendon abnormalities, such as a hypoechoic or anechoic cleft, indicates a partial tear.
Full-thickness tear: This disorder is characterized by complete tendon fiber disruption and tendon retraction. An intact plantaris tendon may be more obvious in the setting of a full-thickness Achilles tendon tear, and should not be mistaken for intact Achilles tendon fibers. Herniation of Kager's fat into the site of a tendon rupture can also be seen, as well as posterior acoustic shadowing from the torn tendon ends (refraction artifact).
Peritendinitis: Isoechoic soft-tissue thickening or hypoechoic fluid surrounding the Achilles tendon indicates peritendinitis.
Haglund's syndrome: A constellation of findings that includes Achilles tendon thickening, fluid in the retrocalcaneal bursa, and osseous prominence at the posterosuperior calcaneus. Retro-Achilles fluid also may be seen with this syndrome.

Other Structures

Plantaris tendon: This is a thin tendon at the medial aspect of the Achilles tendon, often best appreciated in the setting of an Achilles tendon tear. It may be absent in up to 20% of normal individuals.
Kager's fat pad: This structure is echogenic to heterogeneous fatty tissue deep in relation to the Achilles tendon.
Retrocalcaneal bursa: This bursa is located between the Achilles tendon and posterosuperior calcaneus. It may normally contain up to 3 mm of fluid.
Retro-Achilles bursa: This is a potential bursa that is superficial (posterior) to the Achilles tendon at the level of Achilles tendon insertion. In normal individuals, there is no fluid in this bursa.
Gastrocnemius muscle: Injury to the medial head of the gastrocnemius, known as “tennis leg,” is a relative common clinical condition and can be detected easily by ultrasound. It is characterized by disrupted fibers at the aponeurosis with anechoic or hypoechoic fluid/hemorrhage and variable degrees of tendon retraction.

Footnotes

Address correspondence to Q. Dong ([email protected]).
CME—This article is available for CME credit. See www.arrs.org for more information.

Supplemental Content

File (09_3111_thumb_s01.jpg)
File (dong_q_ajr_20090531_achilles_c.wmv)

Information & Authors

Information

Published In

American Journal of Roentgenology
Pages: W173
PubMed: 19696253

History

Submitted: June 2, 2009
Accepted: June 2, 2009
First published: November 23, 2012

Keywords

  1. Achilles tendon
  2. musculoskeletal imaging
  3. ultrasound

Authors

Affiliations

Qian Dong
Both authors: Department of Radiology, University of Michigan Health System, 1500 East Medical Center Dr., TC 2910R, Ann Arbor, MI 48109-5326.
David P. Fessell
Both authors: Department of Radiology, University of Michigan Health System, 1500 East Medical Center Dr., TC 2910R, Ann Arbor, MI 48109-5326.

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