Research Progress Of Artificial Knee Polyethylene Liner

Osteoarthritis (osteoarthritis, OA) is a kind of chronic inflammation of the joint, involving the sclerotin and including synovium, joint capsule and other structures of joint, taking degenerative changes of articular cartilage as the core situation. It is a sterile, chronic, progressive encroachment of joints, especially weight-bearing joints. Its clinical manifestations include articular cartilage damage, osteophytes at the articular surface, synovial hyperplasia, synovitis and joint space narrowing.As the population and life expectancy increases, a variety of bone and joint diseases, especially the incidence of degenerative diseases, becomes more and more frequent.The most effective and successful method of end-stage disease is the artificial knee replacement,。The 10 to 15 year survival rate of TKA prosthesis is currently 85%～90%.It significantly improves joint motor function and quality of life in patients.Ultra-high molecular-weight polyethylene (UHMWPE) has been chosen as the artificial knee, hip and other joint replacement material for over 40 years because of its low friction coefficient and wears rate, good mechanical properties and biocompatibility.But, the osteolysis near artificial prosthesis interface, caused by the interaction between polyethylene liner wear particles and macrophages, lead to long-term loosening of the knee replacement prosthesis.Each year about 100 million joint prosthesis are taken all around the world, and the failure rate of surgery is nearly 10% in 10 years.Since the changes of mechanical properties and resistance irradiation led by sterilization being the main problem of degradation of artificial prosthesis, many responses and new types of polyethylene material have come into being. This thesis describes many aspects of the integrated ultra-high molecular polyethylene and the corresponding extension of the service life of prosthesis measures. In the first place, surface modification of polyethylene using mainly radiation cross linking and surface treatment technologies such as ion implantation, changes the molecular structure, the physical and chemical properties of polyethylene, maintaining the purposes of increasing wear resistance and bio-mechanical compatibility. Secondly, increasing the thickness of polyethylene liner (10mm or so) delays the wear and tear of polyethylene. Again, in order to better simulate the movement characteristics of human knee joint, the Rotating Platform Prosthesis theory was proposed by developers since the 1980's. In this prosthesis, it is rotatable between its polyethylene liner and the tibial component. With the knee joint flexion, tibial polyethylene liner in the metal prosthesis to rotate freely within the orbit of the decomposition of the femur and tibia between the shear force, knee prosthesis design theory to solve low-stress and free to rotate on the conflict between reduce the loosening of the tibial and femoral prosthesis polyethylene liner and a high degree of match, always keep in motion the greatest contact area, reducing the wear of polyethylene pad. To explore new knee prosthesis surface and to design effective prevention of polyethylene wear is a major problem of the research of artificial prosthesis.