Biomimetic Cartilage Implant with Restrictive Swelling Network
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Solution Overview
Problem
Current artificial cartilage implants fail to mimic natural cartilage mechanics, cause stress in adjacent tissues, have fixed sizes, and do not allow post-operative MRI, while regenerative techniques are not immediately load-bearing and require damaging healthy cartilage.
Innovation Solution
An artificial cartilage composed of a fixed negative charged hydrogel infused within a restrictive swelling network of filaments, which restricts swelling to maintain osmotic pressure for load-bearing, allowing for patient-specific size adjustment and post-operative MRI.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a hydrogel implant is allowed to swell freely to maximize load-bearing capacity, then the load-bearing capability is improved, but the implant size becomes uncontrollable and cannot be adjusted intra-operatively
Solution Approach 1:
The implant uses a dynamic spacer network structure that allows controlled swelling of the hydrogel while maintaining adjustable dimensions. The network can adapt its configuration to permit swelling in specific directions while constraining others, enabling both load-bearing performance and size control.
Solution Approach 2:
The patent changes the physical state and swelling parameters of the hydrogel by introducing a restrictive spacer network. This network modifies the swelling behavior from uncontrolled to controlled, allowing the implant to achieve optimal load-bearing properties while maintaining adjustable size through parameter optimization.
2Strength
If the implant structure is made rigid to provide immediate load-bearing support, then the mechanical strength is improved, but the implant cannot mimic natural cartilage mechanics and creates stress in adjacent tissues
Solution Approach 1:
The implant employs local quality differentiation through its spacer network structure, where different regions have different swelling and mechanical properties. This allows the implant to provide strong load-bearing support in compression while remaining compliant in shear, mimicking natural cartilage behavior and reducing stress on adjacent tissues.
Solution Approach 2:
The patent creates a composite structure combining hydrogel material with a spacer network framework. This composite achieves both the strength needed for immediate load-bearing and the compliance required to match natural cartilage mechanics, eliminating the harmful stress concentration in adjacent tissues.
3Reliability
If regenerative techniques are used to promote natural cartilage healing, then long-term regeneration is improved, but the technique is not immediately load-bearing and only successful in young patients
Solution Approach 1:
The implant provides preliminary load-bearing support immediately upon implantation, while simultaneously creating a favorable environment for subsequent cartilage regeneration. The spacer network structure and hydrogel composition are designed to support mechanical loads from day one while promoting cell infiltration and tissue regeneration over time.
Solution Approach 2:
The implant is designed with self-service capabilities where the hydrogel degradation products and spacer network structure actively promote cartilage regeneration. The material provides both immediate mechanical support and long-term regenerative stimulation, making the system self-sufficient for both load-bearing and tissue repair functions.
4Stability of the object's composition
If a dense filament network is used to restrict hydrogel swelling, then the swelling control is improved, but at least 60% volume requirement reduces the effective hydrogel content
Solution Approach 1:
The spacer network is designed as a porous structure with optimized pore size and distribution. This allows the network to effectively restrict hydrogel swelling and maintain structural stability while minimizing the volume occupied by the filaments themselves, ensuring that at least 60% of the implant volume remains as functional hydrogel.
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 solution provides immediate functional load-bearing, allows for patient-specific tailoring, adjustable size, and promotes regeneration, while maintaining osmotic swelling pressure to balance joint loads, ensuring effective cartilage repair and regeneration.
Implementation Method 1
The fixed negative charged hydrogel has a fixed negative charge density of −0.17 to −0.23 mEg/ml and is capable of swelling between 2-15 times compared to the volume of the hydrogel without being restricted
Implementation Method 2
The restrictive swelling network restricts the fixed negative charged hydrogel to swell not more than 10% with respect to the maximum swelling capacity of the fixed negative charged hydrogel without being constraint by the restrictive swelling network
Implementation Method 3
The restrictive swelling network is a spacer network of filaments with a top surface layer, a bottom surface layer, and some of the filaments crossing in a middle area layer between both the top and bottom surface layers limiting and restricting the maximum distance between both the top and bottom surface layers
Implementation Method 4
The fixed negative charged hydrogel within the restrictive swelling network has an equilibrium stiffness between 0.5 and 2 MPa to resist external loads applied to the top surface layer or the bottom surface layer of the artificial cartilage
Data Source
AI summary
An artificial cartilage is provided whereby a fixed negative charged hydrogel has been infused within a restrictive swelling network, which limits and restricts the thickness of the artificial cartilage. At least 60% of the volume of the artificial cartilage is composed of the restricted and swollen hydrogel. The restrictive swelling network restricts the hydrogel to swell not more than 10% with respect to its maximum swelling capacity, i.e. a swelling capacity to swell 10-fold more is retained. The hydrogel within the restrictive swelling network has an equilibrium stiffness between 0.5 and 2 MPa to resist external loads applied to the top surface layer or the bottom surface layer of the artificial cartilage. The hydrogel has a fixed negative charge density of −0.17 to −0.23 mEg/ml and is capable of swelling between 2-15 times compared to the volume of the hydrogel without being restricted.