A fast contact-determination algorithm for in vivo knee kinematics analysis

A near real-time, image-free, contact-determination algorithm is developed for the use of analyzing in vivo kinematics of an artificial knee joint. Using a three-dimensional motion tracker and the knowledge of the precise geometries of the contacting surfaces, the contact regions between two articular surfaces can be determined within seconds. The results are validated with the use of Fuji films, which show high degree of accordance in the contact regions determined. Applications include knee kinematics validation, TKA wear-pattern analysis, and intro-operative surgical assessment.To determine the in vivo contact locations between total knee prosthetic components without the use of any imaging modality.Validated with the Fuji film contact study, this computer algorithm provides an image-free, and accurate way of finding contact regions between prosthetic components.An image-free, near real-time, algorithm is developed to study the in vivo contact condition between prosthetic components.A Dynamic Reference Body (DRB) is attached to each of the Total Knee Arthroplasty component and their motions, while in contact with each other, are tracked with an optical spatial sensor. The geometries of the articular surfaces, represented in point-clouds with point-normal, were obtained from a laser-scanner at 0.4mm resolution. For each recorded pose, the contact between articular surfaces were determined by first matching point normal and then performing a nearest-point search, both facilitated by the use of a generalized binary-search-tree (kd-tree).A size-3 Sigma Knee (Johnson\& Johnson), represented by approximately 31,000/19,000 points for each of the femoral/tibial component, respectively, is used for this study. For each pose, the contact between components can be determined under one second on a 2GHz PC, rendering it applicable for intra-operative use. The contacts between prosthetic components are visualized using standard computer graphics techniques and contrasted with the contact obtained by Fuji film of the same pose. Depicted below, the contact regions determined by these two methods show high degree of accordance with each other. This allows for, in particular, an image-free TKA wear-pattern analysis.

This work was presented at the 60th Canadian Orthopaedics Association (COA) Annual Meeting.

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