Porous Titanium Modular Patella System
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Solution Overview
Problem
Existing patellar implants made entirely of polyethylene face challenges in stabilization due to lack of bone or soft tissue ingrowth, and the use of bone cement can be inaccurate and increase surgery time.
Innovation Solution
A modular patellar implant system comprising a polyethylene posterior portion and a porous metal anterior portion with a mechanical interlock and complementary engaging surfaces, allowing for secure attachment without external fasteners and minimizing bone cement usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If an entirely polyethylene patellar implant is used, then the implant can be easily manufactured and inserted, but it cannot be stabilized because polyethylene surface is not conducive to bone or soft tissue ingrowth
Solution Approach 1:
The patent employs a composite structure combining polyethylene and porous metal materials. The polyethylene component provides ease of manufacture and smooth articulation surface, while the porous metal component enables bone ingrowth and biological fixation. This composite approach resolves the contradiction by integrating the advantages of both materials to achieve both ease of manufacture and reliable stabilization.
Solution Approach 2:
The patent applies different material properties to different regions of the implant. The posterior portion uses polyethylene for smooth articulation and ease of insertion, while the anterior portion uses porous metal for bone ingrowth and biological fixation. This local differentiation of material quality allows the implant to simultaneously achieve ease of manufacture in the polyethylene region and reliable stabilization in the porous metal region.
2Reliability
If bone cement is used to secure the porous metal backing, then the implant can be stabilized, but the surgery time increases and accuracy requirements increase
Solution Approach 1:
The porous metal component is designed to achieve self-service biological fixation through bone ingrowth into the porous structure. This eliminates or reduces the need for bone cement application, allowing the implant to stabilize itself biologically over time. This self-service mechanism resolves the contradiction by providing reliable stabilization without requiring time-consuming bone cement application procedures.
Solution Approach 2:
The patent extracts or eliminates the bone cement component from the implantation process by designing a porous metal structure that achieves direct biological fixation. By removing the bone cement step, the patent reduces surgery time and eliminates the accuracy requirements associated with bone cement application, while maintaining reliable stabilization through bone ingrowth.
3Strength
If external fasteners such as sutures are used to secure the polyethylene implant, then the implant can be attached to the host patella, but the attachment strength is insufficient compared to biological fixation
Solution Approach 1:
The composite structure with porous metal anterior portion enables strong biological fixation through bone ingrowth, replacing the insufficient suture attachment. The porous metal provides a robust biological anchor that achieves superior attachment strength compared to sutures, while the overall modular design keeps the device complexity manageable through standardized components.
Solution Approach 2:
The patent replaces the mechanical suture attachment system with a biological fixation system based on bone ingrowth into the porous metal structure. This substitution transitions from external mechanical fasteners to internal biological anchoring, achieving superior attachment strength while simplifying the overall device by eliminating the need for extensive suture fixation systems.
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 modular system provides stable attachment and resistance to separation through mechanical interlock and tissue ingrowth, reducing surgery time and complications associated with bone cement.
Implementation Method 1
a polyethylene surface may not be conducive to bone or soft tissue ingrowth
Data Source
AI summary
A patellar implant includes a posterior portion and an anterior portion. The posterior portion can have a first radial sidewall that extends between an outboard face and an inboard face. The outboard face can include an articulating surface. The inboard face can include one of a stem and a recess, and one of an annular central hub and an annular radial pocket. The anterior portion can have a second radial sidewall that extends between a tissue engaging surface and a posterior portion engaging surface.