ABSTRACT
A normal joint in our body is made up of bones that are lined by surface cartilage. The joint is surrounded by a capsule with a thin lining of synovial cells that produce a thin layer of lubrication …lm. The lubrication …lm (synovial ¥uid) together with the surface cartilage (articular cartilage) acts as a shock absorber and allows the joint to move smoothly; this protective action endures for many years (such as 50-60 years). If the surface cartilage is badly damaged or if the joint surfaces are misaligned (e.g., hip dysplasia), then the cartilage will wear out much quicker than in normal wear and tear, and as a result, the bone under the cartilage layer becomes exposed. The exposed bone starts to rub against the other and the process of osteoarthritis (wear and tear) is established. Osteoarthritis
25.1 Arti…cial Joint Replacement ................................................................................................. 851 25.1.1Hip Joint Replacement and Its Clinical Performance............................................... 851 25.1.2Knee Joint Replacement and Its Clinical Performance............................................ 853 25.1.3Increase in Hip Joint Arthroplasty Procedures........................................................854 25.1.4Problems of Joint Replacement: Osteolysis.............................................................. 855
25.2 Bearing Materials for Joint Replacements ............................................................................ 857 25.2.1Polyethylene Bearing Material................................................................................. 857
25.2.1.1History of Polyethylene in the Orthopedic Field....................................... 859 25.2.1.2Cross-Linked Polyethylene........................................................................860 25.2.1.3Antioxidants for Polyethylene.................................................................... 862
25.2.2 Phospholipid Polymers for Mimicking Articular Cartilage .....................................864 25.2.2.1Hydration Lubrication................................................................................864 25.2.2.2Articular Cartilage and Material Design...................................................864 25.2.2.3Photo-Induced Surface “Grafting from” Polymerization.......................... 865 25.2.2.4Poly(MPC)-Grafted Polyethylene.............................................................. 867
25.2.3 Poly(Ether-Ether Ketone) Bearing Materials ........................................................... 872 25.2.3.1Structure and Properties............................................................................ 872 25.2.3.2Tribological Properties.............................................................................. 873 25.2.3.3Surface Modi…cation.................................................................................. 873
25.3Fixation Materials for Joint Replacements........................................................................... 875 25.3.1 Poly(Methyl Methacrylate) Bone Cement ................................................................ 875 25.3.2Bone Cement History............................................................................................... 876 25.3.3Problems with PMMA Bone Cement....................................................................... 876 25.3.4Solutions for the Problems of PMMA Bone Cement............................................... 876
25.3.4.1Antibiotic-Loaded Acrylic Cement............................................................ 876 25.3.4.2 Bone Bioactive Organic-Inorganic Hybrid Bone Cement ........................ 877
25.4Future Perspectives............................................................................................................... 877 References...................................................................................................................................... 878
is, therefore, the result of mechanical wear and tear on a joint. Its main feature is a loss of surface cartilage with bone rubbing on bone and this may include joint pain, tenderness, stiffness, creaking, and locking of joints. This process produces pain and local in¥ammation. In osteoarthritis, a variety of potential forces-hereditary, developmental, metabolic, and the mechanical-may initiate processes leading to loss of cartilage. As the body struggles to contain ongoing damage, immune and regrowth processes can accelerate damage. Sometimes the body tries to relieve this pain by increasing the amount of ¥uid in the joint. This is why joints are swollen. The formation of bone spurs and cysts around the joint is another hallmark of osteoarthritis.
