Fully automated computer algorithm for calculating articular contact points with application to knee biomechanics

A fully automated computer algorithm for calculating the articular contact points between two bone surface models is presented. The algorithm requires the bone surface models and their relative positions as inputs in order to resolve the articular contact path. In the case of surface model overlap due to measurement errors or as a solution of an optimization procedure, the result is a volumetric estimation of the space confined between the two surfaces. The algorithm is based on attaching a grid of lines to one bone surface model and calculating the intersecting points of each of the lines in the grid with both bone surface models. The contact points are then determined as the closest points between the surfaces along the lines in the grid. The same contact points are used to evaluate any volume that is confined between two overlapping surface models. The algorithm is ideal for use in biomechanical studies, simulations of joint motion, and optimizations that require an iterative process to determine contact path and relative bone position. The algorithm is applied to a Sawbones knee model that is moved from flexion to extension while being tracked by an optical tracking system. The contact path of the two bones is generated and an example of calculating bone impingement is provided.