Modular Prosthesis Extensions for Revision Surgery
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Solution Overview
Problem
Current knee prostheses face challenges in revision surgery due to the difficulty in removing primary implant components from bone, particularly when bone has grown into extensions, requiring extensive bone resection and complicating the surgical process.
Innovation Solution
A knee prosthesis design featuring modular components with porous metal extensions that allow for easier removal by using titanium foam for bone ingrowth, where the extensions can be sintered to a solid metal base, and the outer surfaces are treated to control friction and bone ingrowth, facilitating surgical disconnection without damaging surrounding bone.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If extensions are made of solid metal to provide structural support and stability, then strength and stability are improved, but ease of removal during revision surgery deteriorates
Solution Approach 1:
The extension is divided into two distinct segments: a solid metal proximal portion for structural support and a porous metal distal portion for bone ingrowth. This segmentation allows each portion to have optimized properties - the solid metal provides the necessary strength while the porous metal enables easier removal through bone ingrowth mechanisms that can be controlled or reversed.
Solution Approach 2:
The extension utilizes a composite structure combining solid metal and porous metal materials. The solid metal portion provides mechanical strength and structural integrity, while the porous metal portion facilitates bone ingrowth and enables controlled removal. This composite approach resolves the contradiction by allowing both strength and ease of removal through different material properties in different regions of the same component.
2Reliability
If extensions are made porous to facilitate bone ingrowth and fixation, then ease of removal deteriorates due to bone integration, but reliability of fixation is improved
Solution Approach 1:
The extension applies different surface qualities to different regions: the proximal portion maintains a solid, smooth surface for structural integrity and controlled removal, while the distal portion features a porous surface structure specifically where bone ingrowth is desired. This local differentiation of material properties allows the extension to achieve reliable fixation through bone ingrowth at the distal end while maintaining ease of removal capability at the proximal end.
3Ease of repair
If extensive bone resection is performed to remove primary implant extensions, then ease of removal is improved, but loss of substance increases
Solution Approach 1:
The porous metal portion is designed in advance to facilitate controlled bone ingrowth that creates a reversible fixation mechanism. This preliminary design of the bone-interactive surface allows for easier removal during revision surgery compared to traditional solid metal extensions, thereby reducing the need for extensive bone resection and minimizing bone loss while still achieving reliable initial fixation.
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
Enables more straightforward removal of prosthetic components during revision surgery, conserving native bone and reducing the risk of complications, while maintaining effective bone integration for fixation.
Implementation Method 1
the extensions can be sintered to a solid metal base, and the outer surfaces are treated to control friction and bone ingrowth
Implementation Method 2
the extensions can be sintered to a solid metal base
Data Source
Figure 1
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Figure 4~5
AI summary
A joint prosthesis system has two implant components (12,14) and a bearing (16). One of the implant components has an articulation surface (18,20) for articulation with the bearing. The other implant component has a mounting surface (26) for supporting the bearing. At least one of the first and second components includes a recess (122,124,126,128,130) and a stud (132,134,136,138,140) in the recess. The joint prosthesis also includes an extension (30,32,34,36,38) mounted on the stud and extending out from the bone-engaging surface to an end (40,42,44,46,48). Part of the extension is received in the recess.