Composite Interbody Device with PEEK Core and Titanium Endplates
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Solution Overview
Problem
Conventional spinal fusion implants face challenges with slow bone growth due to micro-motion, which can disrupt fusion and lead to subsidence and pseudarthrosis, and titanium implants are radiopaque, hindering diagnostic assessment of bone growth.
Innovation Solution
A composite interbody device with a PEEK plastic core and titanium endplates, featuring hydroxyapatite coating and porous structures to encourage on-growth, in-growth, and through-growth, providing enhanced stabilization and visualization without compromising the strength of the implant.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If titanium implants are used, then strength and stability are improved, but radiopacity increases which hinders diagnostic assessment of bone growth
Solution Approach 1:
The implant is divided into two distinct components: a titanium endplate for strength and a PEEK core for radiolucency. This segmentation allows each material to perform its optimal function without compromising the other.
Solution Approach 2:
The implant uses a composite structure combining titanium and PEEK materials. The titanium endplate provides mechanical strength while the PEEK core enables radiolucency for bone growth visualization.
2Reliability
If through-growth fusion method is used, then fusion can be achieved, but the process is slow and can be disrupted by micro-motion
Solution Approach 1:
The device prepares multiple bone growth pathways (on-growth surfaces, in-growth pores, and through-growth channels) in advance, allowing bone to grow simultaneously through multiple routes rather than waiting for slow through-growth alone.
Solution Approach 2:
The device maintains continuous stabilization through its structured support while bone grows through multiple pathways simultaneously, preventing micro-motion disruption and ensuring uninterrupted fusion progression.
3Reliability
If hydroxyapatite is mixed with or applied to PEEK plastic, then bone on-growth is encouraged, but the material becomes embrittled and weakened
Solution Approach 1:
The implant separates the hydroxyapatite coating function to the titanium endplate while the PEEK core remains pure and structurally intact. This segmentation prevents hydroxyapatite from embrittling the PEEK material.
Solution Approach 2:
The titanium endplate acts as an intermediary carrier for the hydroxyapatite coating, allowing bone on-growth promotion without directly compromising the PEEK core's mechanical properties.
4Difficulty of detecting and measuring
If PEEK implants are used to avoid radiopacity, then visualization is improved, but fixation capability deteriorates
Solution Approach 1:
The implant divides functions between materials: titanium endplate provides fixation capability while PEEK core provides radiolucency for visualization.
Solution Approach 2:
The composite structure combines titanium's high fixation capability with PEEK's radiolucency, achieving both strong fixation and clear bone growth visualization simultaneously.
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
The device accelerates spinal fusion by promoting simultaneous bone growth types, minimizing micro-motion, and allowing clear diagnostic assessment through radiolucency, thereby improving fusion stability and visibility.
Implementation Method 1
A hydroxyapatite coating applied to the bone interface sides of the superior and inferior endplates encourages bone growth onto the endplates
Implementation Method 2
bony on-growth onto device surfaces provides relatively quick, albeit limited mechanical rigidity
Implementation Method 3
The bone interface side includes multiple bone interface pores for permitting bone growth therein
Implementation Method 4
in-growth, as achieved with the device described herein, incrementally increases mechanical strength as bone grows into porous features of the interbody device to anchor bone to the device
Implementation Method 5
through-growth, which takes the longest to complete, fully stabilizes and completes the fusion
Implementation Method 6
A metallic inferior endplate includes a core interface side and a bone interface side opposite the core interface side
Implementation Method 7
On-growth and in-growth enhance device stabilization, thus accelerating complete fusion by minimizing micro-motion that could disrupt through-growth
Data Source
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AI summary
A method of manufacturing a composite interbody device is provided, comprising: assembling superior and inferior endplates: wherein the surface features increase surface area of the bone interface layer, to optimize contact with bone at an implant site; and forming a porous core interface layer on the central barrier layer opposite the bone interface layer; diffusion bonding under heat and pressure the core interface layer with the central barrier layer and the bone interface layer coating the bone interface side with hydroxyapatite; placing the inferior and superior endplates in a mold, on each side of a core cavity, with the core interface layers facing the core cavity and the bone interface sides facing away from the cavity; and injection-molding molten plastic into the core cavity, to form a plastic core between the endplates and bonded with core interface sides of the core interface layers; wherein molten plastic extrudes into pores of the core interface layers, to bond with the endplates.