Spinal Interbody Devices with Gradient Porosity
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Solution Overview
Problem
Existing orthopedic implants, such as spinal fusion cages, face challenges in achieving secure fixation to bone, visualizing the implant via radiographic imagery, and maintaining durability while promoting bone ingrowth and reducing stress shielding.
Innovation Solution
The development of spinal interbody devices (IBDs) with optimized features, including varying porosities, tissue through-channels, bioactive substance integration, and composite-like structures with nonporous and porous portions, to enhance fixation, visualization, and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If porous structures are used to encourage bone growth into the implant, then bone ingrowth is improved, but the implant becomes more difficult to visualize via radiographic imagery
Solution Approach 1:
The patent applies local quality by creating a gradient porosity structure where the proximal portion has lower porosity (30-60%) for better radiographic visibility and structural integrity, while the distal portion has higher porosity (60-90%) to maximize bone ingrowth. This spatial variation in porosity allows different regions to serve different functions simultaneously.
Solution Approach 2:
The implant combines porous and non-porous portions in a single composite structure. The non-porous proximal portion provides radiographic contrast and structural support, while the porous distal portion facilitates bone ingrowth. This composite approach resolves the contradiction by integrating materials with opposing properties in a unified device.
2Reliability
If graft windows are provided for bone graft packing, then bone growth into the implant is improved, but the implant's structural strength is reduced due to concentration of loads on smaller areas
Solution Approach 1:
The patent extracts the need for separate graft windows by incorporating porous structures directly into the implant body. This eliminates the need for distinct window openings while maintaining bone ingrowth capability, thereby preserving structural integrity and distributing loads more evenly across the implant.
Solution Approach 2:
The patent merges the bone graft function directly into the implant structure by integrating porous regions that serve as both structural components and bone ingrowth pathways. This consolidation eliminates the separation between graft delivery and structural support functions.
3Strength
If the implant is made stiffer to provide structural strength, then durability is improved, but stress shielding increases which limits bone ingrowth
Solution Approach 1:
The patent applies local quality by creating a gradient porosity structure where the proximal portion has lower porosity (30-60%) for better radiographic visibility and structural integrity, while the distal portion has higher porosity (60-90%) to maximize bone ingrowth. This spatial variation in porosity allows different regions to serve different functions simultaneously.
Solution Approach 2:
The patent utilizes porous materials with controlled porosity gradients to reduce overall implant stiffness while maintaining local structural strength. The porous distal portion (60-90% porosity) reduces stress shielding and promotes bone ingrowth, while the less porous proximal portion (30-60% porosity) maintains structural integrity.
Data Source
AI summary
A method of making a spinal implant may include obtaining images of a vertebra defining a disc space of a patient, identifying a number of porous sections in an implant for implantation in the disc space, and producing the implant including the identified number of porous sections.