Background:
Magnetic resonance imaging (MRI) is useful for evaluating the stability of an osteochondral lesion of the talus (OLT). A T2 high-signal line between the fragment and its bed on MRI is known as a reliable indicator of an unstable lesion. However, the lesion exhibits various conditions even if a T2 high-signal line is observed. The purpose of this study was to evaluate the relationship between the T2 value of a high-signal line and the condition of the area between the fragment and its bed in OLT.

Methods:
T2 values of the T2 high-signal line and those of joint fluid were measured from preoperative MRI images in 46 ankles with OLT and the T2 ratio (high-signal line / joint fluid) was calculated. The relationship between the T2 ratio and CT, arthroscopic, and histologic findings was examined.

Results:
The mean T2 ratio was 0.48. T2 ratios of cystic lesions (0.62) or bone absorption (0.67) in the bed were significantly higher than those without a cyst (0.40) or no absorption (0.40). The T2 ratio of an unstable lesion (0.51) was significantly lower than that of a stable lesion (0.29). In histologic findings, there were 2 separate patterns: chondral and subchondral bone separations. The T2 ratio of the chondral separation (0.60) was significantly higher than that of bone separation (0.48).

Conclusion:
This study showed that the T2 ratio on a high-signal line was a predictor of stability, cyst, and bone absorption in OLT.

Level of evidence:
Level III, comparative series.

アクセプト後にタイトル・アブストラクト等変更あり、著者最終稿は変更前のタイトル"T2 value of high signal line on MRI is related to the conditions around the fragment in osteochondral lesion of talus"