Knee Prosthesis Condyle Curvature Control
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Solution Overview
Problem
Conventional orthopaedic knee prostheses often experience paradoxical anterior translation, leading to loss of joint stability, accelerated wear, and instability in patients due to unnatural motion and forces exerted by surrounding soft tissue, particularly during deep flexion.
Innovation Solution
The design of a posterior cruciate-retaining orthopaedic knee prosthesis with a femoral component featuring a condyle surface curved in the sagittal plane, with specific radii of curvature and contact points at different degrees of flexion, which reduces paradoxical anterior translation by controlling the radius of curvature and transitioning between discrete radii to maintain stability and kinematics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional orthopaedic knee prosthesis design is used, then the prosthesis can replicate natural knee movement, but paradoxical anterior translation occurs leading to loss of joint stability and accelerated wear
Solution Approach 1:
The patent applies parameter changes by modifying the radius of curvature of the condyle surface at different flexion angles. Specifically, the design transitions from a single radius of curvature to multiple discrete radii (e.g., first radius at 0-30 degrees flexion, second radius at 30-60 degrees, third radius at 60-90 degrees), where each radius is carefully selected to control the contact point movement and prevent paradoxical anterior translation while maintaining natural kinematics throughout the range of motion.
2Device complexity
If the condyle surface uses a single radius of curvature, then the design is simpler, but it cannot control contact point movement across different flexion ranges
Solution Approach 1:
The patent applies segmentation by dividing the condyle surface into multiple zones, each with a different radius of curvature. The condyle surface is segmented into at least two distinct regions: a first region with a first radius of curvature for initial flexion (0-30 degrees), and a second region with a second radius of curvature for deeper flexion (30-90 degrees). This segmentation allows independent optimization of contact point behavior in each flexion range, enabling precise control over anterior-posterior translation while maintaining manufacturability.
3Device complexity
If soft tissue forces are not accounted for, then the prosthesis design is simpler, but unnatural motion and instability occur during activities
Solution Approach 1:
The patent applies preliminary anti-action by designing the condyle surface geometry to preemptively counteract the destabilizing effects of soft tissue forces. The multi-radius design is specifically configured so that as soft tissue forces increase during flexion, the contact point naturally transitions between radii in a controlled manner that prevents paradoxical anterior translation. This geometric pre-planning ensures stability during dynamic activities before instability can occur.
Data Source
AI summary
An orthopedic knee prosthesis includes a tibial bearing and a femoral component configured to articulate with the tibial bearing. The femoral component includes 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 may be increased during mid-flexion.