Central pseudodefect of the talus: a potential ankle MR interpretation pitfall.
OBJECTIVE
The purpose of our study was to outline the MR features of the central pseudodefect of the talus (a normal finding that can simulate an osteochondral lesion on ankle MR studies), assess the prevalence of the central pseudodefect of the talus, and provide insight into the origin of this misleading MR appearance.


METHODS
We retrospectively evaluated 31 ankle MR studies in 10 asymptomatic volunteers and 21 consecutive patients for the presence of the central pseudodefect of the talus. None of the patients had a history of trauma to the 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 identified.


RESULTS
Six volunteers (60%) and 13 patients (62%) showed a curvilinear band in the middle third of the talus on far medial sagittal images, consistent 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 few millimeters below the articular surface. On cross-referenced axial and coronal images, the band corresponded to the talar insertion site of the deep tibiotalar fibers of the deltoid ligament.


CONCLUSIONS
The central pseudodefect of the talus is a common finding that is produced by the insertion of the tibiotalar fibers of the deltoid ligament into the talus. Familiarity with its appearance is necessary to avoid misinterpreting it as an osteochondral lesion of the talus.
Rosenberg
Z S
ZS
Department of Radiology, Hospital for Joint Diseases/New York University Medical Center, NY 10003, USA.
Mellado
J
J
D000328:Adult; D000368:Aged; D000843:Ankle Joint / Q000473:pathology*; D003937:Diagnosis, Differential; D003951:Diagnostic Errors / Q000517:prevention & control*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000295:instrumentation / Q000379:methods; D008297:Male; D008875:Middle Aged; D010007:Osteochondritis / Q000175:diagnosis; D012189:Retrospective Studies; D013628:Talus / Q000473:pathology*