A 35-year-old male felt a painful “pop” in his posterior left lower leg while playing football. Afterward, his “foot didn’t work right anymore.” X-ray of the left ankle and tib/fib was normal but he was unable to ambulate. You plan an ultrasound over the area of maximal tenderness and discover the above image (Image 1.Ultrasound of the left posterior ankle 11cm proximal to the calcaneal insertion of the Achilles tendon. Case courtesy of Robert Lystrup.)
Achilles tendon rupture at the myotendinous junction.
- Pearl: Achilles tendon ruptures can be misdiagnosed as ankle sprains, especially if they are partial tears.
The Thompson test [1]. To perform this test, have the patient lie prone with the foot over the edge of the examination table, or with the knee flexed to ninety degrees. The examiner then squeezes the gastrocnemius soleus complex, which should cause plantarflexion of the foot. The test is considered positive and is suggestive of a complete Achilles tendon rupture if the foot fails to plantarflex.
- Pearl: Thompson test is done passively, with the patient prone with their foot overlying the examination table, so as to isolate the gastrocnemius/soleus complex.
Achilles tendon rupture is largely a clinical diagnosis, supported by a palpable defect in the Achilles tendon and a positive Thompson test. A bedside ultrasound can help confirm the diagnosis.
Imaging is not necessary to make the diagnosis of Achilles tendon rupture. If the diagnosis is in question, MRI can be performed on an outpatient basis to confirm the diagnosis.
Image 2: MRI of the L ankle demonstrating acute tear of the achilles tendon at the myotendinous junction with 2cm retraction 11cm from the calcaneal insertion. Case courtesy of Robert Lystrup.
Patients with significant injuries to the Achilles tendon or flexor mechanism of the foot should be made non-weight-bearing and splinted in resting equinus. A posterior splint in thirty degrees of plantarflexion or a CAM boot with a 3-inch high heel lift is appropriate initial management. EM3 has a great video explaining how to splint an Achilles rupture.
- Pearl: A majority of Achilles tears at the myotendinous junction can actually be managed non-operatively [2]. However, they should follow-up with a Sports Medicine or Foot and Ankle specialist within a week of the injury.
Resources & References:
Check out our prior SplintER post on Plantaris tendon rupture which can present similarly.
- Khan-Farooqi W, Anderson RB. Achilles tendon evaluation and repair. The Journal of Musculoskeletal Medicine. 2010;27(5).
- Ahmad J, Repka M, Raikin SM. Treatment of myotendinous Achilles ruptures. Foot Ankle Int. 2013;34(8):1074-1078. PMID: 23513030
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