Phosphorylcholine Grafted Polymer Layer for Wear-Resistant Artificial Joints
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Solution Overview
Problem
Current bearing materials for artificial joints, such as those made from ultra-high molecular weight polyethylene (UHMWPE), suffer from wear debris generation due to friction, leading to osteolysis and loosening, which necessitates frequent replacements and poses challenges in maintaining wear resistance over extended periods, especially in humid environments.
Innovation Solution
A bearing material with a polymer layer having a phosphorylcholine group grafted onto the UHMWPE surface, where the polymer layer thickness is optimized between 10 to 200 nm, and a phosphoric index of at least 0.32 is achieved through photoinduced polymerization, enhancing wear resistance and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a film layer is formed on the UHMWPE surface to improve tribological characteristics, then wear resistance is improved in the initial stage, but the film layer is removed by severe friction over time, causing wear resistance to deteriorate rapidly
Solution Approach 1:
The patent changes the chemical composition parameters of the polymer layer by incorporating phosphorylcholine groups and controlling the ratio of specific monomers (70-90 mol% of one type, 10-30 mol% of another type) to achieve optimal wear resistance that is maintained over extended periods. This compositional optimization prevents the rapid deterioration seen in conventional film layers.
Solution Approach 2:
The patent creates a composite polymer layer combining different monomer units with specific functional groups (phosphorylcholine and another complementary group) to form a material that exhibits superior tribological properties. This composite structure provides both initial wear resistance and long-term durability by preventing film removal through severe friction.
2Reliability
If crosslinked polyethylene (CLPE) is used to reduce wear debris, then wear resistance is improved (wear decreased to one fifth or one tenth), but the clinical application history is short and long-term wear resistance maintenance is unverified
Solution Approach 1:
The patent optimizes the molecular and chemical parameters of the polymer layer by controlling monomer ratios, molecular weight distribution, and crosslinking density to achieve enhanced wear resistance. The specific composition (70-90 mol% of one monomer type, 10-30 mol% of another) creates a material that maintains its wear-resistant properties over extended clinical service periods, addressing the long-term verification gap of CLPE.
3Reliability
If a random copolymer film is fixed onto the UHMWPE surface to provide surface lubrication, then biocompatibility and tribological characteristics are improved, but the film is likely to remove the UHMWPE surface under severe friction
Solution Approach 1:
The patent changes the chemical parameters of the polymer layer by incorporating specific functional groups (phosphorylcholine and complementary groups) that create strong chemical bonds with the UHMWPE substrate. This chemical bonding mechanism, rather than physical adhesion alone, prevents film removal under severe friction while maintaining biocompatibility and surface lubrication properties.
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 significantly reduces wear debris generation and maintains high wear resistance over long periods, potentially eliminating the need for frequent replacements and ensuring stable joint function, while also being suitable for use in other frictional environments.
Implementation Method 1
a phosphoric index of the bearing surface which is calculated by dividing a peak intensity of phosphate group in an infrared spectrum measured on the bearing surface by a peak intensity of the methylene group is not less than 0.32
Implementation Method 2
grafting a polymerizable monomer having a phosphorylcholine group onto the bearing surface of an artificial joint made of UHMWPE, thus providing an artificial joint component made of a polymer material that has a remarkable effect of suppressing wear of the artificial joint
Data Source
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AI summary
The present invention provides a bearing material that is excellent in durability and is capable of maintaining wear resistance over a long period of time. The bearing material of the present invention is a high wear-resistance bearing material 10 for being used under a humid environment comprising: a base body 12 made of a polymer material having a methylene group; and a polymer layer 30 covering a bearing surface 16 of the substrate 12, the polymer layer 30 comprising polymer chains which have a phosphorylcholine group and are grafted from the bearing surface 16, wherein a phosphoric index of the sliding surface 16 which is calculated by dividing a peak intensity of phosphate group in an infrared spectrum measured on the sliding surface by a peak intensity of the methylene group therein is not less than 0.28.