Metal-backed Patella Component with Porous Coating
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Solution Overview
Problem
Conventional patella components in orthopaedic knee prostheses either provide excessive movement, leading to instability, or are overly constrained, failing to adequately mimic the natural joint's articulation and integration with the femoral component, which can affect the longevity and functionality of the implant.
Innovation Solution
A patella component with a solid-metal base featuring pockets with undercuts and a porous-metal coating, combined with a polymer bearing that articulates with the femoral condyles, providing a stable and biocompatible interface that can be 3D-printed as a monolithic metal component, allowing for either dome or anatomic configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a conventional dome patella component is used, then greater movement between the patella component and the femoral component is allowed, but instability occurs
Solution Approach 1:
The patella component is segmented into two distinct parts: a metal base and a polymer bearing. The metal base provides structural stability and fixation to the patella bone, while the polymer bearing enables smooth articulation with the femoral component. This segmentation allows each part to optimize its function independently, resolving the contradiction between movement range and stability.
Solution Approach 2:
The patent employs a composite structure combining metal and polymer materials. The metal base offers strength and rigidity for stable fixation, while the polymer bearing provides low-friction movement and shock absorption. This composite approach allows the implant to simultaneously achieve both stability and adequate movement range, overcoming the limitations of single-material designs.
2Reliability
If an anatomic patella component is used, then the joint articulation is better constrained, but movement between the patella component and the femoral component is limited
Solution Approach 1:
By separating the structural support function (metal base) from the articulation function (polymer bearing), the design achieves both anatomic constraint and adequate movement. The polymer bearing's dome shape provides natural rolling motion while the metal base ensures stable fixation, resolving the trade-off between constraint and movement.
Solution Approach 2:
The polymer bearing can be configured with different geometries (dome or anatomic) to match specific patient needs and surgical requirements. This parameter adjustment allows optimization of the balance between articulation constraint and movement range for individual cases.
3Reliability
If a solid-metal base with porous-metal coating is used, then bony ingrowth is facilitated, but manufacturing complexity increases
Solution Approach 1:
The metal base incorporates a porous-metal coating on its anterior surface that facilitates bony ingrowth and biological integration. The porous structure provides a scaffold for bone cells to attach and grow into, creating a strong biological fixation. While this adds some manufacturing complexity, it significantly improves long-term implant stability and integration.
Solution Approach 2:
The polymer bearing is molded directly onto the metal base in an integrated manufacturing process, combining two components into a single assembly. This merging reduces the number of separate parts and assembly steps, offsetting the complexity added by the porous coating while maintaining the benefits of both materials.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enhances the stability and integration of the patella component with the femoral component, promoting better joint movement and facilitating bony ingrowth, thus improving the longevity and functionality of the orthopaedic knee prosthesis.
Implementation Method 1
a porous-metal coating is disposed on the anterior base surface and the pegs of the solid-metal base
Implementation Method 2
the polymer bearing has a posterior bearing surface configured to articulate with a pair of femoral condyles of a femoral component
Implementation Method 3
each of the pockets has an undercut formed therein
Data Source
Figure 1~3
Figure 4
Figure 5~6
AI summary
An orthopaedic implant includes a patella component (10) having a metal base (14) with a polymer bearing (12) molded thereto. The metal base comprises a posterior base surface (16) provided with pockets (30) and an anterior base surface (22) having a number of pegs (24) configured to be implanted in the patient's natural patella the anterior base surface and the pegs being coated with a porous metal. A method for making a patella component is also disclosed.