A 21-year-old male professional male player presented four weeks after an innocuous inversion injury to his ankle. While he did not immediately think that this was too severe, he had not been unable to return to play due to ongoing discomfort along the lateral aspect of the ankle. Further questioning revealed that prior to this injury he had experienced ongoing lateral ankle pain for about two years.
On examination there was tenderness over the lateral aspect of the ankle. There was a palpable click over the peroneal tendons when the foot was plantarflexed. There was no evidence of tendon subluxation or dislocation.
X-rays of the left foot and ankle were normal. MRI show a significant amount of fluid in the common peroneal tendon sheath compatible with tenosynovitis. There is also a focal longitudinal split tear of the peroneus longus tendon inferior to the lateral malleolus, extending to the peroneal tubercle. There is reconstitution of the tendon prior to it extending under the foot (zone 3). There is an enlarged peroneal tubercle with significant bone marrow edema in the calcaneus and lateral malleolus.
A static and dynamic ultrasound (USS) examination was also performed. The USS further demonstrates the tenosynovitis and focal split tear on the static examination. During active eversion and dorsiflexion, the peroneal tendons ‘bulge’ the peroneal retinaculum with mild subluxation without dislocation. During forced active eversion with plantar and dorsiflexion the peroneal brevis was rotating around the longus posterior to the lateral malleolus with a sudden reduction at the extreme range of motion compatible with intra-sheath subluxation.
The player elected to pursue surgical treatment. An arthroscopic examination confirmed a longitudinal split tear of the peroneus longus tendon and an intra-sheath subluxation at the level of the fibular groove. The tendon was debrided and repaired, the superior peroneal reticular reconstructed and the hypertrophic peroneal tubercle excised. The player made a good post-operative recovery and was able to return to professional play.
Peroneal tendon tears may result from an acute injury or from chronic degeneration. They can have different orientations. Acute injuries have been described after an ankle inversion injury, tendon subluxation, or laceration along the distal fibula. They can be difficult to diagnose as the presenting symptoms are often vague with lateral ankle pain, oedema, and swelling being common. There are three zones along the peroneal longus tendon. Zone 1 extends from the tip of the lateral malleolus to the peroneal tubercle, Zone 2 from the lateral trochlear process to the inferior retinaculum, and Zone 3 from the inferior retinaculum to the cuboid notch. Zone 3 is a high-stress area, particularly at the cuboid notch, and is the location of the majority of peroneus longus tears.
Magnetic resonance imaging (MRI) is a sensitive and specific examination to diagnose peroneal tendon injuries. Ultrasound, which is cost effective and readily available, has a distinct advantage since dynamic examination can be performed which can clearly demonstrate tendon instability that cannot be evaluated during a static MRI examination. One limitation to ultrasound is it requires a certain level of expertise and experience in order to obtain diagnostic static and dynamic images.
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