Tibial Prosthesis Porous Surface Gradient for Revision Ease
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Solution Overview
Problem
In knee replacement surgeries, the removal of primary knee prostheses with extensions like pegs or stems is challenging due to bone ingrowth, requiring large bone resection and complicating revision surgeries, which can lead to soft tissue irritation and bone compromise.
Innovation Solution
A tibial implant component with a solid metal portion and a porous metal portion, where the porous metal portion has a higher static coefficient of friction on its distal surface and a lower coefficient on its peripheral surface, treated to reduce porosity and irritation, allowing for easier dislodging during revision surgery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the porous metal portion has high porosity on the distal surface to promote bone ingrowth, then fixation strength is improved, but soft tissue irritation increases and removal difficulty increases
Solution Approach 1:
The patent applies different surface properties to different regions of the porous metal portion. The distal surface maintains high porosity (60-80%) to promote bone ingrowth and achieve strong fixation, while the peripheral surface is treated to reduce porosity and create a smoother finish that minimizes soft tissue irritation. This local differentiation of surface quality resolves the contradiction between needing high porosity for fixation and low porosity for tissue compatibility.
2Object-affected harmful factors
If the peripheral surface is treated to reduce porosity and friction, then soft tissue irritation is minimized, but bone ingrowth capability is reduced
Solution Approach 1:
The patent selectively treats only the peripheral surface to reduce porosity and friction, while leaving the distal surface with high porosity intact. This localized treatment ensures that bone ingrowth capability is preserved at the distal surface where it is most needed for fixation, while the peripheral surface becomes more tissue-friendly. The spatial separation of functional requirements resolves this contradiction.
3Strength
If extensions are made fully porous to allow bone ingrowth, then fixation is improved, but revision surgery complexity increases due to difficult removal
Solution Approach 1:
The patent creates a gradient of porosity along the extensions, with the distal portions having high porosity for bone ingrowth and fixation, while the proximal and peripheral portions have reduced porosity. This gradient structure allows bone to integrate with the implant for strong fixation, but the reduced porosity regions provide planes of easier separation during revision surgery, reducing surgical complexity compared to fully porous extensions.
4Strength
If the distal surface has high static coefficient of friction, then bone ingrowth is promoted, but soft tissue contact becomes more irritating
Solution Approach 1:
The patent maintains high static coefficient of friction on the distal surface through high porosity to promote bone ingrowth, while treating the peripheral surface to reduce friction and porosity for soft tissue contact areas. This local differentiation of friction characteristics ensures that high friction benefits bone integration without compromising soft tissue compatibility, resolving the contradiction between these two requirements.
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 minimizes soft tissue irritation, reduces the need for large bone resection, and facilitates easier removal of the implant components during revision surgeries, conserving healthy bone and reducing complications.
Implementation Method 1
The porous metal portion has a higher static coefficient of friction on its distal surface
Implementation Method 2
treated to reduce porosity and irritation
Data Source
AI summary
A joint prosthesis system is suitable for cementless fixation. The system has two metal implant components and a bearing. One of the metal implant components has an articulation surface for articulation with the bearing. The other metal implant component has a mounting surface for supporting the bearing. One of the metal implant components includes a solid metal portion and a porous metal portion. The porous metal portion has surfaces with different characteristics, such as roughness, to improve bone fixation, ease removal of the implant component in a revision surgery, reduce soft tissue irritation, improve the strength of a sintered bond between the solid and porous metal portions, or reduce or eliminate the possibility of blood traveling through the porous metal portion into the joint space. A method of making the joint prosthesis is also disclosed. The invention may also be applied to discrete porous metal implant components, such as augment.