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 kinematics, particularly at mid to late degrees of flexion.
Innovation Solution
A posterior stabilized orthopaedic knee prosthesis with a femoral component featuring a pair of spaced condyles and a posterior cam, and a tibial bearing with a platform and spine, where the condyle surface has varying radii of curvature and contact points at different degrees of flexion, and the posterior cam engages the spine to control kinematics and reduce anterior translation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a typical orthopaedic knee prosthesis is designed to duplicate natural movement, then the prosthesis allows flexion and extension with anterior-posterior motion, but paradoxical anterior translation occurs leading to loss of joint stability and accelerated wear
Solution Approach 1:
The femoral component features a condyle surface with varying radii of curvature in the sagittal plane. The radius of curvature increases from the anterior to posterior aspect of the condyle, creating a non-uniform curved surface that controls the contact point location during flexion. This curvature design prevents paradoxical anterior translation by maintaining the contact point in a posterior position on the tibial bearing.
Solution Approach 2:
The invention changes the geometric parameters of the condyle surface by using varying radii of curvature rather than a constant radius. This parameter variation allows the contact point to be controlled at different locations during the range of motion, specifically keeping it posterior during mid to late flexion to prevent anterior translation and maintain joint stability.
2Device complexity
If the condyle surface has a constant radius of curvature, then the prosthesis structure is simpler, but paradoxical anterior translation occurs at mid to late degrees of flexion
Solution Approach 1:
The femoral component features a condyle surface with varying radii of curvature in the sagittal plane. The radius of curvature increases from the anterior to posterior aspect of the condyle, creating a non-uniform curved surface that controls the contact point location during flexion. This curvature design prevents paradoxical anterior translation by maintaining the contact point in a posterior position on the tibial bearing.
3Reliability
If the posterior cam engages the spine early in flexion, then kinematics are controlled more effectively, but the range of motion before cam engagement is limited
Solution Approach 1:
The condyle surface geometry is designed to control the contact point in a posterior position during early to mid flexion before the posterior cam engages the spine. This preliminary control through surface geometry allows the prosthesis to maintain stable kinematics without cam engagement, and the cam then provides additional control when engaged at later flexion angles.
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 radius of curvature of the condyle surface may be increased during mid-flexion.