Summary

The HU value of the subchondral bone of the talus was lowest in the posterior part of the talus, so the talar subchondral bone quality evaluated by the HU values may not be related to occurring OLTs.

Abstract

Background

Osteochondral lesions of the talus (OLTs) are lesions of the articular cartilage of the talus and underlying the subchondral bone, which occur most frequently in the centromedial zone of the talus. In OLTs, the quality of the subchondral bone may be contributing to damage to the overlying cartilage. Clinically, it has been reported that Hounsfield Unit (HU) values on computed tomography (CT) allow quantitive evaluation of the bone quality. In addition, the HU values correlate with bone mineral density measurements at the femoral neck and lumbar spine. Therefore, we hypothesized that the subchondral bone quality of the talus may be related to occurring OLTs and the HU values in the centromedial zone would be lower than in the other zones of the talus. The purpose of this study was to evaluate the HU values of the healthy subchondral bones of the talus.

Methods

The authors retrospectively analyzed patients who underwent CT of the ankle at our hospital between August 2017 and March 2024. Exclusion criteria were patients younger than 18 years and older than 60, patients with histories of ankle trauma, patients with histories of surgery in lower extrimities, and patients with histories of systemic inflammatory diseases such as rheumatoid arthritis. We assigned nine zones to the talar dome articular surface in an equal 3 × 3 grid configuration according to the previous studies, and the HU values of the region of interest (ROI) were measured. The ROI in a 20-mm2 circle in the subchondral bone on CT sagittal images was evaluated on the talus in each 9-zones.

Results

A total of 43 ankles of 40 patients (26 men, 14 women, mean age 35.3 ± 13.1 years) were included in this study. In each 9-zones, the mean HU value was 605.2±143.5 in the anteromedial zone, 529.6±146.0 in the anterocentral zone, 596.5±148.1 in the anterolateral zone, 530.9±127.8 in the centromedial zone, 521.7±139.9 in the centrodirect zone, 561.2±148.5 in the centrolateral zone, 456.7±124.7 in the posteromedial zone, 434.5±124.4 in the posterocentral zone, and 392.4±113.4 in the posterolateral zone, respectively. The mean HU value in the posterolateral zone was the lowest, but there were no significant differences in the mean HU value between each the zones. Dividing the three row groups (anterior, cental and posterior group), the mean HU value was 577.1±148.6 in the anterior group, 537.9±139.0 in the central group, and 427.9±122.9 in the posterior group, the mean HU value in the posterior group was significantly lower than the mean HU values in the anterior and central groups. In addition, dividing the three column groups (medial, central and lateral groups), there was no significant differences in the mean HU values between the three groups.

Conclusions

The HU value of the subchondral bone of the talus was lowest in the posterior part of the talus. The talar subchondral bone quality evaluated by the HU values may not be related to occurring OLTs.