We present a system to measure geometric properties (e.g., volume, surface area, and contact area) of the cartilage layer in human ankle joints. The cartilage and subchondral bone surfaces are sampled with a stereophotogrammetric device. A configurable pipeline of processing steps is applied to the sampled surface data to compute the desired quantities.
The meshes are cleaned (i.e., disconnected parts removed, holes filled, and noise reduced) and aligned to each other such that they represent the cartilage layer as closely as possibly. A hierarchical stitching approach creates from two separate (opposing) meshes a single closed surface, which is used for volume calculations.
The method has been evaluated with data from 12 lower leg specimens. While our approach confirms the results of previous contact area studies for low curvature regions of the inspected cartilage and bone surfaces, it is superior to existing (mostly mechanical) methods for highly curved regions.
We also discuss biomechanical testing of articular cartilage and present a custom-built prototype for obtaining stiffness maps of biological soft tissue.