Method of design of human joint prosthesis

Abstract

A method of designing a prosthesis having convex male and concave female mating portions is provided for a human joint comprising a condylar male portion the surface of which is generated by the piecewise analysis of an anatomical condyle, which can be an average condyle or a selected condyle, or a distortion of an average condyle to fit the observed general dimensions of a specific patient, and the female portion having at least flexion and laxity surfaces, the flexion surfaces of which are generated by plotting the path of articulation of substantial points of contact between said male portion and a corresponding anatomical female component for said joint through the full normal extension-flexion range plus normal rotation and posterior-anterior displacement for that joint, and the laxity surfaces of said female member comprising raised guide-bearing surfaces for resisting dislocation of the condylar portion, the height and angle, and therefore, the resistance to dislocation, of which guide bearing surfaces increases as a function of deviation from the central motion path of said male portion and as a function of the flexion angle, and which at full laxity for any given angle of flexion corresponds substantially to the forces of anatomical ligamentous restraint of said anatomical joint at the limits of laxity.