Quantification of ankle articular cartilage topography and thickness using a high resolution stereophotography system.

OBJECTIVE: To describe the topography and to measure thicknesses, surface areas and volumes in the cartilage layers of the ankle.
METHODS: Twelve cadaveric ankle joints were disarticulated and the cartilage surfaces of each bone were imaged with a highly accurate (+/-2 microm) stereophotography system (ATOS). The cartilage was then dissolved and the subchondral bone imaged. The geometric data were then used to measure the quantitative parameters in each cartilage layer.
RESULTS: The mean cartilage volume across the 12 specimens ranged from 0.32+/-0.08 ml for the fibula to 2.44+/-0.48 ml for the talus. The mean thickness of both the talar (1.1+/-0.18 mm) and tibial (1.16+/-0.14 mm) cartilage was significantly thicker than the fibula (0.85+/-0.13 mm). The talus had the greatest mean maximum cartilage thickness (2.38+/-0.4 mm).
CONCLUSIONS: The reported stereophotographic technique may be used as an independent gold standard for validation of the accuracy of quantitative cartilage measurements made using magnetic resonance imaging. The thickness distribution maps show that the thickest articular cartilage occurs over the talar shoulders where osteochondral lesions commonly occur and not in the centre of the talar dome as commonly believed.