Reverse Knee Prosthesis Cupule Design for Wear Reduction
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Solution Overview
Problem
Conventional knee resurfacing prostheses experience high wear and reduced efficacy due to stress concentration at small contact surfaces, and require cruciate ligaments for stability, limiting motion and implant life.
Innovation Solution
A reverse knee resurfacing design featuring a femoral component with a cupule shape and a tibial component with a trochlea shape, allowing increased contact surface area and eliminating the need for cruciate ligaments through anterior and posterior lips for stability, distributing pressure loads and enhancing motion ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional knee resurfacing prostheses with small contact surfaces are used, then the implant structure is simple, but wear increases and implant life decreases due to stress concentration
Solution Approach 1:
The patent inverts the conventional prosthesis geometry by making the femoral component concave (cupule-shaped) rather than convex, and the tibial component convex (trochlea-shaped) rather than flat. This reverse geometry fundamentally changes the contact mechanics, distributing stress over a larger surface area and eliminating wear problems associated with small contact surfaces while maintaining structural simplicity.
Solution Approach 2:
The patent employs curved surfaces throughout the implant design - the femoral cupule has a concave spherical geometry, the tibial trochlea has a convex curved surface with a groove, and the polyethylene liner has a spherical outer surface. These curvatures enable large contact areas and smooth rolling motion, reducing stress concentration and wear while improving implant durability.
2Ease of operation
If conventional femoral condyle geometry is used, then the implant design is straightforward, but cruciate ligaments are required for stability, limiting motion range
Solution Approach 1:
The patent extracts and eliminates the requirement for cruciate ligaments by incorporating stabilizing lips directly into the femoral component. The anterior and posterior lips of the cupule provide mechanical constraints that replace the function of the cruciate ligaments, allowing patients with ligament deficiencies to receive the implant without requiring intact ligaments for stability.
Solution Approach 2:
The femoral cupule component performs multiple functions: it provides the primary articulating surface for load bearing, incorporates anterior and posterior lips for stability and constraint, and enables both flexion/extension and rotational movements. This multi-functional design eliminates the need for separate ligamentous structures while providing comprehensive knee joint functionality.
Data Source
Figure 1
Figure 1A
Figure 2
AI summary
A reverse knee prosthesis for use in knee replacement surgery having a femoral component and a trochleal component. The femoral component comprises a stem, which is affixed in a femur, and a femoral cup having a generally concave portion which is sized to articulate on the trochleal component. The femoral cup also comprises a posterior lip and an anterior lip wherein the anterior lip is longer than the posterior Hp. The trochleal component is affixed to a tibial fray which in turn is affixed to the tibia and has a transverse curved body with a narrowed waist. The generally concave portion of the femoral cup has a ridge extending outwardly therefrom, the ridge being sized to articulate on the narrowed waist.