In a knee joint prosthesis, a tibial component for mounting on a tibial plateau which has been appropriately resected and trimmed in a manner removing as little bone as possible to provide:
- a substantially flat upper surface defining a plateau on a plane normal to the axis of the intramedullary canal of said tibia to expose the cancellous bone centrally of said plateau, and to expose the upper rim of the relatively hard peripheral cortical wall;
- a narrow cylindrical opening in the cancellous bone extending from said upper surface substantially down into the tibia on the axis of the intramedullary canal of the tibia;
- and,
- two lateral slots in said upper surface extending down into the cancellous bone of said tibia, said slots being in communication with and extending radially outwardly from said cylindrical opening into the areas of maximum hardness of the cancellous bone of said tibia in planes disposed at an angle of between about ten degrees and thirty degrees to the transverse plane of the joint which passes through the axis of said intramedullary canal respectively;
- said tibial component comprising:
- (a) a base plate having a thickness, and being contoured and shaped to approximate the size and shape of said plateau;
- said base plate further having posterior, left, right, and anterior edges;
- a top surface;
- and an under surface;
- said under surface being contoured so as to substantially match the contour of said plateau, and said top surface defining recessed areas adjacent the right and left edges of the base plate separated by an upwardly projecting area extending between said posterior and anterior edges of said base plate substantially centrally thereof, and flanked by upwardly projecting portions adjacent the posterior and anterior edges of the base plate, said base plate futher defining walls in its posterior edge forming an opening which provides an unobstructed path for the posterior cruciate ligament of said joint to pass upwardly for attachment to the anterior portion of the femur of said joint;
- (b) means having a first and second surface and substantially the same peripheral contour as said base plate mounted on the top surface of said base plate such that said first surface is adapted to receive and support condylar portions of said joint, and said second surface defines a contour which substantially directly abuts the top surface of said base plate;
- (c) a fixation pin on the under surface of said base plate aligned (relative to the contour of said base plate) with said cylindrical opening in said plateau, and dimensioned to fit therein, when said base plate is mounted on, and in abutment with, said trimmed and prepared plateau;
- (d) means on the under surface of said base plate for anchoring said base plate against both shear and rotational forces relative to said plateau comprising a pair of elements dimensioned to fit into, and substantially fill, the cross sectional area of said slots, each element having a proximal end, a distal end, a top edge, a bottom edge, a proximal portion adjacent said proximal end, and a distal portion adjacent its distal end, said elements being respectively affixed along their top edges to the underside of the base plate and along their proximal ends to said fixation pin so as to extend radially outwardly from the fixation pin under the recessed areas of said base plate at angles corresponding to the angles at which said slots extend from said cylindrical opening in said plateau so that said elements fit within said slots when said base plate is mounted on, and in abutment with, said trimmed and prepared plateau, the maximum height of the proximal portion between the top edge and the bottom edge of each said element being substantially smaller than the maximum height of the distal portion between the top edge and the bottom edge of each said element,
- whereby an extremely stable and strong tibial component is provided having a minimum vertical height, but maximum strength and wear characteristics.