Madtown Sono

Middle-aged male with ankle pain

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By Rudi Zurbuchen, MD
Edited by Hani I. Kuttab, MD and Leah Anderson, MD

Clinical Case

A middle-aged male presented to the emergency department (ED) with complaints of right foot pain and difficulty walking. The patient stated that he was playing basketball with his friends last night. He was pivoting with the basketball after a rebound and when taking off he felt a “pop” in his right ankle, followed by considerable pain. He attempted to ambulate, though this only exacerbated the pain. He returned home and placed ice on the affected area and went to bed. The following morning, there was no improvement in his symptoms, and he reported continued difficulty with walking.

A bedside ultrasound was performed:

Figure 1A. Evaluation of the Achilles tendon in the long axis view

Figure 1B. Evaluation of the Achilles tendon in the long axis view

Figure 2. Evaluation of the Achilles tendon in the short axis view

Diagnosis

Complete Achilles Tendon Tear. Bedside ultrasound showed a discontinuity in the Achilles tendon, concerning for a complete rupture. Orthopedic surgery was consulted who recommended outpatient follow up to discuss operative management. The patient was placed in a splint in slight plantar flexion, provided with crutches, and discharged from the ED.

Discussion

Bedside ultrasound can assist with rapid identification of various tendon injuries, including the Achilles tendon. Achilles tendon injuries are typically located 4-6 cm above the calcaneal insertion site in a hypovascular region. Risk factors for tendon rupture include episodic athletes, fluoroquinolone use and steroid injections. Classically, the diagnosis is made clinically (e.g., a positive Thompson test, a palpable defect over the Achilles, and weak plantarflexion). Point-of-care ultrasound can assist in securing the diagnosis, and also assisting in differentiating between partial and full tendon tears. Hartgerink et. al., evaluated sonographic versus surgical findings and noted that ultrasound had 100% sensitivity and 83% specificity when differentiating between complete and partial tears.

How do I do it?

Ultrasound of the Achilles tendon is actually quite easy to perform. If able, it is easiest to have the patient in the prone position with their feet hanging off the edge of the bed (Figure 3). The Achilles is a superficial structure, so the high-frequency linear transducer should be used. Don’t be afraid to use lots of gel in these cases! Patients will often have pain and tenderness over the site of the rupture — so ultrasound gel is your friend to minimize pressure over the area. We recommend scanning the Achilles tendon in two planes (long and short, as above) and comparison with the contralateral side.

Figure 3. Technique for ultrasound examination of the Achilles tendon (Taken from Adhikari et al, 2012). The patient should be in the prone position with the feet partially hanging off the edge of the bed. This helps to improve visualization of the Achilles tendon.

What to look for?

There are various findings associated with tendon injuries, but centers primarily on disruption of the normal fibers seen in tendons. Other signs include a hematoma formation at the site of rupture (as seen above), posterior acoustic shadowing at the margins of the rupture, and possible retraction of the tendon. Dynamic movement of the foot/ankle can also aid in visualizing this separation, and further helps us distinguish between partial and complete ruptures. With slight dorsiflexion and plantarflexion of the ankle under sonographic visualization, separation of one tendon end away from the other with fluid in between them indicates a full-thickness rupture (as above). If continuous movement of the tendon across the site of the rupture is visualized, this suggests a partial rupture of the tendon, with some in-tact fibers.

Teaching Points

  1. Ultrasound use in the diagnosis of musculoskeletal injuries can be incredibly helpful, especially in regard to injuries to the Achilles tendon. Try it the next time you suspect a tendon rupture!
  2. Signs of tendon rupture primarily includes disruption of the normal fibers seen in tendons. Scan slowly and be sure to use plenty of gel when assessing the Achilles tendon.
  3. Dynamic ultrasound can help distinguish between complete and partial Achilles tendon injuries. If movement of the tendon over the site of possible rupture is visualized, this is suggestive of at least a partial Achilles tendon tear.

References

1. Dong Q, Fessel DP. Achilles tendon ultrasound technique. AJR Am J Roentgenol. 2009 Sept;193(3).W173.
2. Hartgerink P, Fessel DP, Jacobson JA, van Holsbeeck MT. Full- versus partial-thickness Achilles tendon tears: sonographic accuracy and characterization in 26 cases with surgical correlation. Radiology. 2001 Aug; 220(2):406-12.
3. Robinson P. Sonography of common tendon injuries. AJR Am J Roentgenol. 2009 Sep; 193(3): 607-18
4. Karadsheh M. Achilles tendon rupture. Orthobullets. Updated 6/7/2021. https://www.orthobullets.com/foot-and-ankle/7021/achilles-tendon-rupture
5. Adhikari S, Marx J, Crum T. Point-of-care ultrasound diagnosis of acute Achilles tendon rupture in the ED. Am J Emerg Med. 2012 May;30(4):634.e3-4. doi: 10.1016/j.ajem.2011.01.029. Epub 2011 Mar 15. PMID: 21406322.