Review Question - QID 218719

The torn structure in Figure A is the peroneus brevis tendon, which runs superior to the peroneal tubercle at the level of the sinus tarsi (above the peroneus longus) to insert into the base of the fifth metatarsal.

Pathology of the peroneal tendons represents a common cause of chronic lateral ankle pain. Injury is typically caused by forced eversion and dorsiflexion of the ankle. The course of the peroneus brevis is deep to the longus (closer to the fibula) and superior to the peroneal tubercle at the level of the sinus tarsi (Illustration B). When assessing an MRI for peroneal tendon tears, it is important to note that there should only be two structures behind the fibula. When three distinct structures appear to exist, there is typically a longitudinal split-type tear of one of the tendons (Illustration A), with the elongated peroneus brevis tendon often seen to wrap partially around the peroneus longus tendon, a finding termed the "boomerang sign" (Illustration C). Peroneal tendon tears of <50% of tendon width can typically be debrided and repaired/tubularized, but those with degeneration of >50% of the tendon require excision and tenodesis.

Recht et al. review MRI of the foot and ankle as a modality that is playing an increasingly important role in the diagnosis of a wide range of foot and ankle abnormalities, as well as in planning for their surgical treatment. The authors note that, on MR imaging, normal peroneal tendons are of similar size and homogeneous low signal intensity, with the peroneus longus tendon being ovoid, but the peroneus brevis tendon typically having a flattened appearance in the retromalleolar groove. They conclude that although complete ruptures of the peroneal tendons are uncommon, longitudinal splits of the peroneus brevis tendon have been increasingly recognized and may appear either as a C-shaped structure at or below the level of the lateral malleolus, which partially wraps around the peroneus longus tendon or as a completely bisected tendon.

Plamanovich et al. describe peroneal tendon tears and their relation to the peroneal tubercle. The authors note that tears of the peroneal tendons may occur in different anatomical sites, with the most prevalent site being around the lateral malleolus at the retromalleolar groove. They also note that, anatomically, the lateral surface of the calcaneus can be divided into thirds, with the middle third including the peroneal tubercle, which separates the peroneus longus tendon from the peroneus brevis and represents a structure that may lead to chronic irritation that could ultimately cause a longitudinal tear. They conclude that chronic friction, particularly of the peroneus longus tendon, over a hypertrophic peroneal tubercle can lead to stenosing tenosynovitis and longitudinal tears.

Figure A is a T1 coronal MRI slice showing a longitudinal split tear of the peroneus brevis tendon. Illustration A represents this with a red arrow. Illustration B depicts the peroneal tubercle that divides the peroneus brevis and longus. Illustration C is another peroneus brevis tendon tear that demonstrates the "boomerang sign" (arrow) as it wraps around the peroneus longus.

Incorrect Answers:
Answer 1: This describes the course of the peroneus longus tendon.
Answer 2: This describes the course of the posterior tibialis tendon.
Answer 3: This describes the course of the tibialis anterior tendon.
Answer 5: This describes the course of the flexor hallucis longus (FHL) tendon.