Sex- and age-related variations in the three-dimensional orientations and curvatures of the articular surfaces of the human talus

Background The high prevalence of foot pathologies in women and the elderly is suggested to be linked to sex- and age-related differences in the calcaneal morphology. Given that, it is expected that there also exists sex- and age-related differences of the articular morphology in the keystone of the foot, the talus. The present study investigated the orientation and curvature of the three articular surfaces of the talus in relation to sex and age based on computer tomography (CT). Methods The CT images of 56 feet were used in this study. The orientations of the talocrural, subtalar, and talonavicular joints were quantified three-dimensionally by calculating normal and principal axes of the articular surfaces defined by planar approximation. The curvature radii of the articular surfaces were also quantified by cylindrical and spherical approximations. Results The talonavicular surface was significantly more twisted and less internally rotated in females than in males. With aging, the subtalar articular surface was significantly facing more posteriorly. Moreover, it was found that the curvature radii of the trochlea and navicular articular surfaces significantly increased with aging, indicating the flattening of the articular surfaces. Conclusion The sex- and age-related differences in talar articular morphology were observed. The substantial degeneration pattern of the talar morphology with aging could potentially lead to a higher prevalence of foot disorders in the elderly.

PIECEWISE-PLANAR APPROXIMATION OF LARGE 3D DATA AS GRAPH-STRUCTURED OPTIMIZATION

<p><strong>Abstract.</strong> We introduce a new method for the piecewise-planar approximation of 3D data, including point clouds and meshes. Our method is designed to operate on large datasets (e.g. millions of vertices) containing planar structures, which are very frequent in anthropic scenes. Our approach is also adaptive to the local geometric complexity of the input data. Our main contribution is the formulation of the piecewise-planar approximation problem as a non-convex optimization problem. In turn, this problem can be efficiently solved with a graph-structured working set approach. We compare our results with a state-of-the-art region-growing-based segmentation method and show a significant improvement both in terms of approximation error and computation efficiency.</p>