Remote Fellowship – Foot & Ankle Fundamentals – 11/2/2020
Case 1 – Discussion
Peroneus Brevis Tear
Peroneal tendon pathology is a common cause for lateral ankle pain, second to lateral capsuloligamentous injuries. Peroneal tendinopathy/tearing occurs most frequently due to overuse/chronic repetitive microtrauma and is less commonly the result of acute trauma from inversion injuries.
Anatomical anomalies play an important role in pathogenesis. The major anatomical variants that may contribute to peroneal tendon pathology include: a low lying peroneus brevis muscle belly, laxity of the superior peroneal retinaculum, hypertrophy of the peroneal tubercle, a flat or convex retromalleolar groove of the fibula, and the presence of the peroneus quartus muscle. The peroneus quartus muscle typically originates from the peroneus brevis muscle and has a variable insertion distally at the retrotrochlear eminence or the peroneal tubercle. When present, it may cause overcrowding and friction among the peroneal tendons in the retromalleolar groove.
When imaging the peroneal tendons on MRI, it is important to be wary of the “Magic Angle Effect”. This is an artifact that occurs with sequences having shorter TE values (including T1-weighted and PD sequences) when the tendons are imaged at approximately 55 degrees relative to the main magnetic field. When this happens, the tendons will appear hyperintense, thus potentially being mistaken for tendinopathy. This artifact can be minimized by positioning the patient’s ankle in plantar flexion.
The peroneus brevis tendon most commonly shows degenerative changes or tears at the level of the retromalleolar groove, and less commonly, near its insertion onto the styloid process of the 5th metatarsal.
On MRI, imaging features of tears depend on the tendon’s location between the retromalleolar groove and peroneus longus tendon. At the retromalleolar groove, an uninjured peroneus brevis tendon appears flat to mildly crescentic in shape and is anterior to the peroneus longus tendon. With a longitudinal tear however, the peroneus brevis often demonstrates a C-shaped or “boomerang” appearance that partly envelops the peroneus longus tendon. There may be increased intrasubstance signal intensity on both T1- and T2-weighted images, and tendon distortion may be noted.
Peroneus brevis tendon is the most commonly injured tendon of the foot in an ankle sprain.
Peroneus brevis tear in a 60-year-old woman with no known injury, now complaining of left ankle pain.
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