Metal and plastic composite tibial component for knee joint

Claim 1

A load bearing tibial component of a knee prosthesis comprising: (a) a supporting metal base plate which is comprised of a lower plate surface, an upper plate surface, and a peripheral edge, the peripheral edge including a plurality of notches spaced apart from each other around the peripheral edge, and; (b) a plastic bearing portion which is integrally molded onto the upper surface of the supporting metal base plate, such that the plastic completely covers the upper surface of the metal base to form a desired bearing surface, and wherein the plastic flows through and fills the notches and completely surrounds the peripheral edge to form a thickness of plastic which extends beyond the peripheral edge of the metal base plate, and forming a lower plastic rim surface wherein the area of said lower plastic rim surface is no greater than 15% of the area of the lower surface of the metal base, said lower plastic rim surface being flush with the perimeter of the lower surface of the metal base plate, creating a metal/plastic seam, and wherein the area of the plastic rim is substantially less than the area of the lower metal plate surface, and wherein a secure mechanical interlock is created between the metal plate and plastic portion.