Stable Interbody Implant With Intra-Implant Motion Control
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Solution Overview
Problem
Existing standalone interbody implants exhibit motion between the implant and bone at the bone-to-implant interface, leading to pain, fibrous tissue formation, and pseudoarthrosis, which are not adequately addressed by current devices.
Innovation Solution
Designing interbody implants that limit or eliminate motion at the bone-implant interface by allowing intra-implant movement, utilizing 3D printing and multi-piece construction with flexible flexures and porous surfaces to facilitate bone integration and reduce motion, and incorporating tailored stiffness through geometry modifications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If standalone interbody implants are designed to maintain motion between adjacent vertebrae, then spinal mobility is preserved, but motion occurs at the bone-to-implant interface causing pain and pseudoarthrosis
Solution Approach 1:
The implant is divided into distinct functional zones: a motion-permitting central region and stable end regions with fixation elements. This segmentation allows motion to be contained within the implant body while maintaining stability at the bone interface, resolving the contradiction between mobility preservation and interface stability.
Solution Approach 2:
Different regions of the implant have different mechanical properties - the central region is designed to be more compliant to allow motion, while the end regions are designed with higher stiffness and fixation elements to ensure stable bone-to-implant attachment. This local differentiation resolves the contradiction by assigning different functions to different parts.
2Reliability
If fixation elements are used to secure the implant to bone, then bone-to-implant interface stability is improved, but the complexity of the device increases
Solution Approach 1:
The fixation elements are integrated directly into the implant body as a unified structure rather than being separate components. This merging reduces device complexity while maintaining the stability function, as the fixation elements are formed as part of the implant manufacturing process rather than requiring separate assembly steps.
3Reliability
If the implant body is made more rigid to reduce motion at the bone interface, then interface stability is improved, but intra-implant motion capability is reduced
Solution Approach 1:
The implant body is segmented into a rigid end region for stable bone attachment and a more compliant central region for motion accommodation. This segmentation allows the implant to simultaneously achieve interface stability through rigid fixation elements while maintaining intra-implant motion capability through the compliant central portion.
Solution Approach 2:
The implant incorporates dynamic characteristics through its compliant central region that allows controlled deformation and motion, while the end regions maintain rigidity for stable fixation. This dynamic design enables the implant to adapt to physiological motion while maintaining bone interface stability.
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 implants provide stability and preserve spinal motion by minimizing bone-implant interface motion, reducing pain and fibrous tissue formation, and alleviating pseudoarthrosis while promoting bone growth and integration.
Implementation Method 1
porous and/or roughened surfaces and/or volumes of the implant facilitate boney attachment of the bone to the implant
Data Source
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AI summary
Implants include one or more pieces that are designed to replace joint motion from the implant-bone interface to an interface within the implant. Because the motion occurs within the implant instead of at the implant-bone interface, the implants relieve pain, reduce fibrous tissue formation, and alleviate pseudoarthrosis. Implants can have tailored stiffnesses by modifying the geometry of the contact surfaces within the implant and or by modifying flexures of the implant. Primary fixation of the implant to the bone using screws, blades, or other fixation devices decreases motion at the bone-implant interface. The flexibility of the implant itself decreases motion between the bone and the implant at the bone-implant interface. Additionally, porous and/or roughened surfaces and/or volumes of the implant facilitate boney attachment of the bone to the implant, further reducing the likelihood of movement at the bone-implant interface.