Current knee replacement designs do not reproduce normal knee kinematics. Polyethylene wear is problematic in current designs. Our Goal was to design a total knee replacement (TKR) that maintains A/P stability and axial rotation, with low polyethylene wear.
Conclusions[10, 11, 12]
- Allows PCL preservation
- Provides A/P stability similar to ACL deficient valgus knees that develop a concave lateral compartment [1].
(See Figure 9) - Allows for normal axial rotations.
- Imposes less A/P constraint (shear forces) than medial pivot.
- Accommodates and controls the cruciate deficient patterns of motions without undue constraint (Medial pivot knees seek to change the pattern of motion through articular constraint).
- Technically forgiving implantation.
Fig. 7.
Conceptual design for a 3DKnee (left) tibial insert for the Foundation™ total knee system that would utilize the current femoral component. The lateral compartment is fully congruent in extension and allows 15o of axial rotation. As the knee flexes, a greater range of femoral motion is possible, but is controlled by the concave lateral compartment.
Fig. 8. At 90 degrees of flexion (left), the 3DKnee tibial insert provides greater than 20 degrees of axial rotation. The femur can rotate externally more than 15 degrees to accommodate the patella. In extension (right), the lateral pivot tibial insert provides for approximately 15 degrees of axial rotations, but controls anterior/posterior motion between the femur and tibia.
Fig. 9. A resected left tibial plateau from a valgus knee shows the characteristic dished lateral compartment that occurs in both ACL intact and deficient arthritic knees [1].
Fig. 10. Sketch of a left total knee replacement with a 3D Tibial insert. The insert obtains maximal contact surface to minimize poly wear, and controls excessive anterior/posterior tibial-femoral motions while permitting free axial rotations.
Allows PCL preservation
Provides A/P stability similar to ACL deficient valgus knees that develop a concave lateral compartment [1].