Central pseudodefect of the talus: A potential ankle MR interpretation pitfall

Purpose: The purpose of our study was to outline the MR features of the cen tral pseudodefect of the talus (a normal finding that can simulate an osteo chondral lesion on ankle MR studies), assess the prevalence of the central pseudodefect of the talus, and provide insight into the origin of this misl eading MR appearance. Method: We retrospectively evaluated 31 ankle MR studies in 10 asymptomatic volunteers and 21 consecutive patients for the presence of the central pse udodefect of the talus. None of the patients bird a history of trauma to th e ankle. The signal, size, and shape of the pseudodefect were documented in each patient. The sagittal images were cross-referenced with the axial and coronal images in all patients in whom the central pseudodefect was identi fied. Results: Six volunteers (60%) and 13 patients (62%) showed a curvilinear ba nd in the middle third of the talus on far medial sagittal images, consiste nt with the central pseudodefect of the talus. The band measured 8-15 x 3-8 mm (mean 11 x 4 mm) and was hypointense on T1 and STIR pulse sequences. In two cases, the pseudodefect was subchondral; in the rest, it was found a f ew millimeters below the articular surface. On cross-referenced axial and c oronal images, the band corresponded to the talar insertion site of the dee p tibiotalar fibers of the deltoid ligament. Conclusion: The central pseudodefect of the talus is a common finding that is produced by the insertion of the tibiotalar fibers of the deltoid ligame nt into the talus. Familiarity with ifs appearance is necessary to avoid mi sinterpreting it as an osteochondral lesion of the talus.