Bone-Anchor Implant Strut Surface for Fixation and Bone Ingrowth
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Solution Overview
Problem
Existing medical implants struggle to form a strong mechanical bond with natural bone both at the time of implantation and after bone growth, despite the use of rough or porous surfaces for bone ingrowth or ongrowth.
Innovation Solution
The implant design includes a first solid region and a second region with interconnected struts that define openings for bone growth, featuring variations in strut length, local empty volume fraction, and surface features like cantilevers and macroscopic surface-interrupting structures made of interconnected struts, manufactured through additive processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If rough or porous surfaces are used on implants, then bone ingrowth or ongrowth is encouraged, but the mechanical bond strength at the time of implantation is insufficient
Solution Approach 1:
The implant surface is segmented into distinct regions: a smooth region for initial mechanical bonding and a porous region for bone ingrowth. This segmentation allows each region to perform its specific function optimally without compromising the other, resolving the contradiction between immediate bond strength and long-term integration.
Solution Approach 2:
Different regions of the implant surface are given different local qualities - the smooth region provides high mechanical strength for initial bonding, while the porous region provides high surface area and porosity for bone ingrowth. This local differentiation resolves the contradiction by allowing each property to excel where needed.
2Duration of action of stationary object
If porous surfaces are used to encourage bone ingrowth, then long-term stability improves, but initial mechanical bonding at implantation is weak
Solution Approach 1:
The implant surface is divided into functionally distinct smooth and porous regions, allowing the smooth region to provide strong initial mechanical bonding while the porous region ensures long-term stability through bone ingrowth, thus resolving the temporal contradiction.
Solution Approach 2:
The smooth region performs the preliminary action of providing strong mechanical bonding at implantation, creating a stable foundation that allows the porous region to subsequently facilitate bone ingrowth for long-term stability, addressing the sequential timing issue.
3Ease of manufacture
If uniform strut structures are used in the implant, then manufacturing is simplified, but bone growth conditions are not optimized across different regions
Solution Approach 1:
The strut structure transitions from uniform to non-uniform, with different regions having different strut densities, lengths, and configurations. This allows optimization of bone growth conditions in each region while maintaining manufacturability through systematic design variations.
Solution Approach 2:
The strut parameters (length, diameter, spacing, density) are systematically varied across different regions of the implant to optimize bone growth conditions locally, while still using the same manufacturing process, thus resolving the contradiction between manufacturing simplicity and biological optimization.
Data Source
AI summary
In embodiments of the invention, an implant that anchors into bone may have a bone-facing region that comprises a plurality of interconnected struts. The interconnected struts may define local features such as engagement ridges, fins, crests, a macroscopic surface-interrupting feature, a divertor structure, and sawteeth in any combination. Such features may help resist translation or rotation of the implant, and may be conducive to bone ingrowth. Parameters such as local empty volume fraction and local average strut length can be varied, even within the features, by the design of the network of struts. Struts may be tapered. Cantilever struts may also be provided, which may point in a desired direction. The pattern of struts may be specified to the level of dimensions and location of individual struts. The implant may be manufactured by additive manufacturing methods. The mesh of struts may be generated by an algorithm using Voronoi tessellation.