Osteochondral lesions of the talar dome (OLT) involve the articular cartilage and subchondral bone. The subchondral bone plate (SBP) plays a crucial role in cartilage metabolism, and its disruption no longer maintains cartilage homeostasis. Computed tomography (CT) can provide more precise information on subchondral bone. CT image prediction of the histological findings on OLT will be useful to determine the most appropriate therapeutic strategy. We hypothesized that the clarification of the relationship between CT image of subchondral bone and histological findings of articular cartilage in osteochondral fragment will predict the cartilage degeneration in OLT. The purpose of this study is to evaluate the unique features of the CT findings that relate to the condition of the articular cartilage in OLT.

Thirty ankles in 29patients, who had OLT with an osteochondral fragment were retrospectively reviewed. At surgery, the osteochondral fragment of 19ankles could be preserved (preservation group) by fixation or drilling, and in the remaining 10ankles the osteochondral fragment was removed (excision group). Preoperative CT findings were compared between the 2groups. Biopsies of the osteochondral fragment from 13ankles were performed. The relationship between the CT and histological findings were evaluated.

The area of lesion in the preservation group was significantly larger than that in the excision group. The CT images of the lesion showed the rate of absorption of the SBP in the preservation group to be lower than that in the excision group. As for the lesion bed absorption, it was higher in the preservation group than in the excision group. In the excision group, all cases showed bed sclerosis while bed sclerosis was observed in 42.1% of cases in the preservation group. The specimens with disruption of the subchondral bone plate exhibited cartilage degeneration and abundant chondrocyte cloning. OLT with absorption of the SBP on CT showed severe cartilage degeneration, while the remaining SBP on CT showed low-grade cartilage degeneration.

This study shows the features of preoperative CT and histological findings in OLT with osteochondral fragments. The condition of the subchondral bone plate affects the cartilage degeneration. CT findings provide important information for the determination of surgical treatment.