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Research

Background

Joint Prostheses

 With the growing of aged people, the number of arthritis patients is growing. Application of joint replacements to patients bring the recovery of walking ability and relief of severe pain. However, in certain cases, the revision operation are applied due to the loosening of joint prostheses which is usually derived from wear debris-induced osteolysis.

 Although several new trials for wear reduction of joint prostheses materials, there  still remain the unsolved problems on wear and wear debris-induced biological reactions.

Lubrication of Natural Synovial Joint

 Natural synovial joint is excellent bearing system with low wear and low friction. During normal walking, the elastohydrodynamic lubrication (EHL) is likely to play the main role in preserving low wear and low friction. Under severe thin film conditions with local contacts at start-up after long standing, however, various supplemental lubrication mechanisms such as weeping, biphasic, boundary and gel film lubrication modes seem to operate to protect articular cartilage. This synergistic lubrication mechanism contribute to maintain low wear and low friction and is called the adaptive multimode lubrication.

 However, the lubrication mode of artificial joints are mainly mixed and boundary lubrication and excellent lubrication mechanisms of natural synovial joint are not reproduced in artificial joints. Therefore, we considerd that elucidation of mutual relation among various lubrication mode in synovial joint and introduction of adaptive multimode lubrication mechanism to artificial joints lead to create the breakthrough artificial joint system with super lubricity and durability.


Structure of superficial layer of natural articular cartilage (left)
and adaptive multimode lubrication in natural synovial joint (right)


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Hydrogel Artificial Cartilage

 To achieve the artificial joints based on bionic design, we focus on the hydrogels with material properties similar to natural articular cartilage. In previous study, PVA( poly(vinyl alcohol)) hydrogel as candidate material of artificial cartilage showed excellent lubricity and enhancement of fluid film formation comparing to UHMWPE that is representative material of artificial joints in joint simulator test and numerical analysis.


Frictional behavior and thickness of fluid film in artificial knee joints


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Aims

 In our previous study, application of hydrogel as artificial cartilage material leads to enhancement of fluid film formation and significant reduction of friction. however, further improvement of strength, durability and super lubricity of hydrogels based on bionic design should be needed for clinical application.
 Therefore, to solve these problems, professionals majored in mechanical engineering(Biomechanics & Biotribology), gel science(Biomaterials) and orthopaedics(Biomedical) gathered and launched this project. Final target of this project is the establishment of clinical application of bionic artificial cartilage with superior function and longevity




 The details of research activities are shown in the pages listed below.

Biomechanics-Biotribology Field
Biomaterials Field
Biomedical Field