The Case:
A 32-year-old man with no past medical history presented to the ED with left posterior ankle pain after playing basketball. He stated he jumped and felt an immediate “pop” and pain in the posterior leg. He has been unable to ambulate due to the pain. On exam, he had a positive Thompson test on the left calf. Radiographs were negative for acute fracture, but point of care ultrasound (POCUS) displayed findings demonstrative of an Achilles tendon injury.
Why It Matters:
Achilles tendon rupture is most common in men and most prevalent in ages 30-40; however, it can affect anyone of all ages when activity levels are increased. Typically, the patient will report suddenly exerting force on the Achilles tendon through abrupt pivoting or rapid acceleration (such as jumping). Frequently, individuals will recall hearing/feeling a “pop” and have sudden onset pain and difficulty walking; however, the absence of these symptoms does not rule it out either. The Thompson test has historically been sufficient to diagnose an Achilles tendon rupture. To perform this test, place the patient in the prone position with their feet off the bed and squeeze the gastrocnemius muscle while observing the foot for plantarflexion. If the foot does not plantarflex, the test is positive and concerning for rupture.
While this test has a reported sensitivity and specificity of 96% and 98%, respectively, there can be obstacles causing an up to 10% missed diagnosis rate when the test is negative. For example, suppose there is a significant amount of swelling. In that case, if the patient is guarding due to pain or if the patient has a larger body habitus, it may be difficult to correctly perform the exam and see the presence or absence of plantarflexion. Plain films do not typically aid in the diagnosis other than to look for any fractures. However, an easy, cost-effective, and radiation-free tool to have at the bedside to aid in this diagnosis is ultrasound. To further clinch the diagnosis, combining these two tools utilizing the Realtime Achilles Ultrasound Thompson (RAUT) test would allow you to visualize with ultrasonography the (lack of) Achilles movement while squeezing the gastrocnemius muscle if there was any discrepancy. Disruption in the tendon with surrounding edema suggests tendon rupture (Figures 1 and 2). Regarding management, the patient should be placed in a splint with the affected ankle in slight plantarflexion (20 degrees), instructed to remain non-weight bearing, and follow up with orthopedics.
Figure 2: Ultrasound of the bilateral Achilles tendon with the affected side observing a collection of anechoic fluid (yellow arrow) adjacent to tendinous structure with distorted anatomy compared to unaffected side.
Authored by Megan Buranosky MD, Victoria Gonzalez MD, and Scott Sherman MD
References:
Griffin MJ, Olson K, Heckmann N, Charlton TP. Realtime Achilles Ultrasound Thompson (RAUT) Test for the Evaluation and Diagnosis of Acute Achilles Tendon Ruptures. Foot & Ankle International. 2017;38(1):36-40. doi:10.1177/1071100716669983
Maffulli N. The clinical diagnosis of subcutaneous tear of the Achilles tendon. A prospective study in 174 patients. Am J Sports Med. 1998;26(2):266-270. doi:10.1177/03635465980260021801