Knee prosthesis having non-uniform stiffness

A unicondylar knee prosthesis comprising:

• a polymer unicondylar tibial insert;
• and
• a unicondylar tibial tray comprising:
• a unicondylar insert platform having a top surface configured to support the polymer unicondylar tibial insert and a bottom surface opposite the top surface, wherein the unicondylar insert platform is formed from a titanium material and has a substantially uniform stiffness gradient, and
• a tibial base attached to the bottom surface of the unicondylar insert platform and extending distally therefrom, wherein the tibial base is configured to be secured to a surgically-prepared proximal end of a patient's tibia and includes a straight inboard side configured to abut a sagittal plane cut of the patent's tibia when the tibial base is secured to the proximal end of the patient's tibia and a curved outboard side opposite the straight inboard side, wherein the tibial base is formed from a Body-Centered Cubic (BCC) lattice structure and is defined by multiple sections when viewed from the cross-sectional coronal plane and each section has a uniform stiffness that is different from each other section, and wherein the multiple sections includes an inboard-most section that includes the straight inboard side, an outboard-most section that includes the curved outboard side, and at least one central section located between the inboard-most section and the outboard-most section, wherein the inboard-most section has the least stiffness of the multiple sections, the outboard-most section has the greatest stiffness of the multiple sections, and the at least one central section has a stiffness between the stiffness of the inboard-most section and the outboard-most section, and wherein the stiffness of the inboard-most section, the outboard-most section, and the at least one central section are configured to reduce a magnitude of a stress riser occurring at the sagittal plane cut of the patient's tibia when the tibial base is secured to the proximal end of the patient's tibia.

A method for fabricating a unicondylar knee prosthesis, the method comprising:

• determining a non-uniform stiffness gradient for a tibial base of the unicondylar knee prosthesis, wherein the non-uniform stiffness gradient defines a variation in stiffness of the tibial base from an inboard side of the tibial base to an outboard side of the tibial base when viewed from a cross-sectional coronal plane;
• fabricating the tibial base based on the determined non-uniform stiffness gradient, wherein the tibial base is configured to be secured to a surgically-prepared proximal end of a patient's tibia and includes a straight inboard side configured to abut a sagittal plane cut of the patent's tibia when the tibial base is secured to the proximal end of the patient's tibia and a curved outboard side opposite the straight inboard side, wherein the tibial base is defined by multiple sections when viewed from the cross-sectional coronal plane and each section has a uniform stiffness that is different from each other section, and wherein the multiple sections includes an inboard-most section that includes the straight inboard side, an outboard-most section that includes the curved outboard side, and at least one central section located between the inboard-most section and the outboard-most section, wherein the inboard- most section has the least stiffness of the multiple sections, the outboard-most section has the greatest stiffness of the multiple sections, and the at least one central section has a stiffness between the stiffness of the inboard-most section and the outboard-most section, and wherein the stiffness of the inboard-most section, the outboard-most section, and the at least one central section are configured to reduce a magnitude of a stress riser occurring at the sagittal plane cut of the patient's tibia when the tibial base is secured to the proximal end of the patient's tibia;
• and
• attaching the fabricated tibial base to a bottom surface of a unicondylar insert platform to form the unicondylar knee prosthesis, wherein the unicondylar insert platform includes a top surface configured to support a unicondylar tibial insert and has a substantially uniform stiffness gradient.