Tear of the peroneus longus tendon: MR imaging features in nine patients

PURPOSE: To determine the magnetic resonance (MR) imaging features that cha racterize tear of the peroneus longus tendon at the midfoot. MATERIALS AND METHODS: Medical records and MR images in nine patients with a tear of the middle segment of the peroneus longus tendon were retrospecti vely I;reviewed. All nine patients had undergone routine ankle MR imaging; three had undergone additional oblique coronal MR imaging. Surgical proof o f a tear was available for three patients. RESULTS: Partial tear was present in four patients, and complete tear was p resent in five. Partial tears were characterized by heterogeneous signal in tensity and thickening of the tendon. Complete tears were characterized by discontinuity of the tendon. Additional findings included fluid in the tend on sheath (n = 6), marrow edema of the lateral calcaneal wall (n = 3), enla rged peroneal tubercle (n = 3), and tear of the peroneus brevis tendon (n = 2). The extent of the tear was better assessed with oblique coronal MR Ima ges. CONCLUSION: The characteristic MR imaging appearance of complete or partial tear of the middle portion of the peroneus longus tendon includes foci of increased signal intensity in the distal tendon, morphologic alterations, a nd/or discontinuity of tendon. Bone marrow edema along the lateral calcanea l wall may be suggestive of the diagnosis. Additional oblique coronal midfo ot MR images may help in assessment of the extent of the tear.