Hard-Tissue Implant Pillar Slot Design for Stress Shielding
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Solution Overview
Problem
Conventional hard-tissue implants face issues such as stress shielding, resorption of affected hard tissue, and insufficient space for tissue growth due to surface texturing, which are not adequately addressed by existing designs, particularly in applications beyond the spine where load-bearing conditions vary significantly.
Innovation Solution
A hard-tissue implant design featuring a bulk implant with pillars and slots, where the pillars are distributed across an area of at least 80 mm² and extend distally, with a Young's modulus of elasticity of at least 10 GPa, and a volume ratio of slots to pillars between 0.40:1 and 0.90:1, allowing for immediate load transfer and preventing stress shielding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If surface texturing is added to implants to improve mechanical anchoring, then early fixation strength is improved, but the surface texturing occupies excessive volume of the implant interface, leaving insufficient space for hard tissue growth
Solution Approach 1:
The implant surface is segmented into distinct functional zones: a load-bearing zone with texturing for mechanical anchoring, and a tissue-growth zone with smooth surfaces and pores for hard tissue ingrowth. This segmentation allows each zone to optimize its specific function without compromising the other.
Solution Approach 2:
Different regions of the implant surface have different properties: the load-bearing zone has rough texturing for strong mechanical anchoring, while the tissue-growth zone has smooth surfaces and controlled porosity to facilitate hard tissue ingrowth. This local differentiation resolves the contradiction by providing appropriate surface characteristics in each specific area.
2Strength
If the implant interface is designed with continuous implant phase to improve structural integrity, then mechanical strength is improved, but the discontinuous tissue phase cannot form properly, leading to stress shielding and tissue resorption
Solution Approach 1:
The implant interface is segmented into load-bearing regions with continuous implant structure for structural integrity, and tissue-integration regions with discontinuous implant phase (pores and smooth surfaces) that allow continuous hard tissue phase formation. This segmentation enables both continuous phases to coexist in their respective zones.
Solution Approach 2:
The design transitions from a two-dimensional surface texturing approach to a three-dimensional interface architecture with controlled porosity and distinct zones. This dimensional change allows the implant to provide both structural integrity and tissue integration pathways simultaneously through vertical and horizontal spatial organization.
Data Source
AI summary
Hard-tissue implants are provided that include a bulk implant, a face, pillars, and slots. The pillars are for implantation into a hard tissue. The slots are to be occupied by the hard tissue. The hard-tissue implant has a Young's modulus of elasticity of at least 10 GPa, has a ratio of the sum of (i) the volumes of the slots to (ii) the sum of the volumes of the pillars and the volumes of the slots of 0.40:1 to 0.90:1, does not comprise any part that is hollow, and does not comprise any non-pillar part extending to or beyond the distal ends of any of the pillars. Methods of making and using hard-tissue implants are also provided.