Knee Prosthesis Condyle Curvature Control
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Solution Overview
Problem
Typical orthopaedic knee prostheses experience paradoxical anterior translation, leading to loss of joint stability, accelerated wear, and instability in activities due to unnatural motion and forces from surrounding soft tissue, particularly at mid to late degrees of flexion.
Innovation Solution
A posterior stabilized orthopaedic knee prosthesis with a femoral component featuring a pair of condyles with curved surfaces and a posterior cam, designed to articulate with a tibial bearing, which includes a platform and spine, controlling the kinematics by maintaining or increasing the radius of curvature of the condyle surface to delay anterior translation and promote posterior translation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the condyle surface has a typical radius of curvature design, then the prosthesis can be manufactured with standard geometry, but paradoxical anterior translation occurs at mid to late degrees of flexion causing joint instability and accelerated wear
Solution Approach 1:
The patent applies parameter changes by modifying the radius of curvature of the condyle surface from a typical decreasing profile to one that maintains or increases the radius of curvature at mid to late degrees of flexion. This geometric parameter change alters the contact mechanics between the femoral component and tibial bearing, delaying the onset of paradoxical anterior translation and improving joint stability throughout the range of motion.
Solution Approach 2:
The patent utilizes curvature principles by designing the condyle surface with controlled radius of curvature characteristics. Specifically, the curved surface geometry is engineered to maintain or increase curvature radius in the sagittal plane at mid to late flexion angles, which changes the roll-back mechanism and prevents unnatural anterior translation of the femoral component on the tibial bearing.
2Reliability
If the condyle surface geometry is modified to control translation, then joint stability and wear resistance improve, but the manufacturing complexity and design precision requirements increase
Solution Approach 1:
The patent defines specific parameter ranges for the radius of curvature of the condyle surface, particularly specifying that the radius should be maintained or increased at mid to late degrees of flexion. By establishing quantifiable geometric parameters and their relationships, the patent provides clear manufacturing specifications that balance the need for improved wear resistance with achievable manufacturing precision requirements.
3Reliability
If the posterior cam engagement is optimized to control kinematics, then the onset of anterior translation is delayed to later degrees of flexion, but the device complexity increases
Solution Approach 1:
The patent employs the posterior cam and spine as intermediary structures that mediate the interaction between the femoral component and tibial bearing. These elements serve as mechanical intermediaries that control the timing and manner of engagement between the femoral and tibial components, thereby delaying anterior translation to later degrees of flexion while providing predictable kinematic control throughout the range of motion.
Data Source
AI summary
An orthopaedic knee prosthesis includes a tibial bearing and a femoral component configured to articulate with the tibial bearing. The femoral component includes a posterior cam configured to contact a spine of the tibial bearing and a condyle surface curved in the sagittal plane. The radius of curvature of the condyle surface decreases gradually between early-flexion and mid-flexion. Additionally, in some embodiments, the posterior cam of the femoral component may include a concave cam surface and a convex cam surface.