Porous Unit Cell Lattice Surfaces With Interlocking Fixation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for creating computer-generated models of porous structures often result in surfaces that are prone to debris formation and require additional steps like bone cement for stability, which can compromise bone ingrowth and mechanical integrity.
Innovation Solution
A process involving the creation of computer-generated models with porous geometries where struts are modified to ensure they are fully connected and supported, with nodes repositioned to enhance surface stability and eliminate the need for bone cement by forming interlocking features and fixation elements that extend beyond the boundary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If struts are truncated at the outer surface to achieve near-net shape, then the external shape is achieved, but the porous geometries become unsupported and prone to debris formation
Solution Approach 1:
The patent applies preliminary action by extending struts beyond the outer surface boundary before fabrication, ensuring that porous geometries have adequate support throughout the build process. This pre-positioning of structural elements prevents debris formation during manufacturing while still achieving the desired near-net shape after controlled removal of excess material.
2Stability of the object's composition
If bone cement is used to provide initial stability, then stability is achieved, but bone ingrowth is compromised and mechanical integrity is reduced
Solution Approach 1:
The patent applies the taking out principle by completely eliminating bone cement from the system. Instead of using cement to provide initial stability, the design extends porous geometries beyond the outer surface boundary to create self-supporting structures that provide both immediate stability and pathways for bone ingrowth without cement interference.
Solution Approach 2:
The extended porous geometries serve themselves by providing both structural support and bone ingrowth pathways simultaneously. The structures that extend beyond the boundary self-support the porous geometries during fabrication and later facilitate bone ingrowth, eliminating the need for separate cement application.
3Strength
If nodes are repositioned to enhance surface stability, then surface robustness is improved, but the complexity of model preparation increases
Solution Approach 1:
The patent applies local quality by repositioning nodes specifically at the outer surface boundary where they are visible after fabrication, while maintaining regular node distribution in the interior. This localized modification enhances surface robustness and reduces debris formation only where needed, without unnecessarily complicating the overall model preparation process.
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
This approach results in robust surfaces that reduce debris formation and provide initial stability without the need for bone cement, enhancing bone ingrowth and mechanical integrity while minimizing risks associated with cement use.
Implementation Method 1
a detailed description of the use of selective laser melting technology may be found in U.S. patent application Ser. No. 10/704,270, filed on Nov. 7, 2003, now U.S. Pat. No. 7,537,664
Implementation Method 2
The powder is sintered, by the application of laser energy that is directed in raster-scan fashion to portions of the powder layer corresponding to a cross section of the article
Implementation Method 3
One example of a modern rapid prototyping technology is a selective laser sintering process. According to this technology, articles are produced in layer-wise fashion from a laser-fusible powder that is dispensed one layer at a time. The powder is sintered, by the application of laser energy
Data Source
AI summary
Aspects of the present disclosure relate generally to preparing models of three-dimensional structures. In particular, a model of a three-dimensional structure constructed of porous geometries is prepared. A component file including a porous CAD volume having a boundary is prepared. A space including the porous CAD volume is populated with unit cells. The unit cells are populated with porous geometries having a plurality of struts having nodes on each end. The space is populated with at least one elongated fixation element extending beyond the boundary to produce an interlocking feature enabling assembly or engagement with a mating structure.