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See page 1588 for the question.
DIAGNOSIS
Osteochondral lesion of the talus.
Imaging findings
The initial MRI (figure 3) identified subchondral oedema-like signal of the medial talus on the fluid-sensitive short tau inversion recovery (STIR) sequence. The T1-weighted sequence was normal. A small effusion was present and the talar cartilage, ligaments and tendons were normal (not shown).
(A) Coronal short tau inversion recovery at initial presentation shows diffuse oedema-like signal involving the subchondral bone of the superomedial talar dome. (B) The sagittal T1 is normal, area within the dashed line corresponds to the oedema-like signal region observed in (A).
Anteroposterior and lateral plain radiographs obtained at 18 months (figure 4) identified a 7 mm subchondral cyst within the medial talar dome. The talar dome was intact and there was no collapse of the cortex.
(A) Anteroposterior radiograph performed 18 months after initial presentation demonstrated a well-demarcated lucency within the superomedial talar dome (arrow head), the overlying cortex is intact. (B) Lateral radiograph identified lucency within the mid zone of the talar dome (dashed line).
The second MRI (figure 5) showed a predominately high-T2 signal, low-T1 signal lesion within the subcortical bone corresponding to the original area of oedema-like signal in the presentation MRI (figure 3) and the cystic lucency on the 18 months radiograph (figure 4). A curvilinear focus of high signal immediately beneath the hyaline cartilage (figure 5A,B) was a component of the subchondral cyst rather than chondral separation. The joint effusion had increased marginally in size and small loose bodies were present (not shown).
(A,B) Coronal short tau inversion recovery and T2 sequences 18 months after initial presentation showed a well-demarcated, high-signal lesion involving the superomedial talar dome (arrow heads). Diffuse oedema-like signal surrounded the lesion. (C) Sagittal T2 fat saturation sequence demonstrates the depth and anteroposterior extent of the …
Footnotes
Contributors All authors have contributed significantly to the concept and design, analysis and interpretation of data, drafting the article and revising it critically for important intellectual content and final approval of the version to be published.
Competing interests None.
Provenance and peer review Not commissioned; externally peer reviewed.