Papers by Keyword: Artificial Joints

Abstract: Bioinert ceramics in use today are the result of more than 60 years of continuous development. Early studies were concentrated on alumina that in the late 1960s was the most advanced ceramic, and on pyrolytic carbon. After tests in orthopedic bearings, pyrolytic carbon found clinical applications in artificial heart valves, where it is in clinical use so far. After 1970 zirconia-toughened ceramics (YTZP, ZTA, ATZ) were investigated in view of their use as biomaterials in orthopedics. Especially the introduction of YTZP in clinics in the 1990s gave a new momentum to the use of inert bioceramics. So far, zirconia-toughened ceramics are replacing alumina because of their outstanding mechanical properties leading to high reliability in ceramic components. The behavior of ZTAs and ATZs are exploited in several innovative devices. Especially metal-free devices are of interest, because of the increasing number of patients sensitized to metals. Using zirconia-toughened ceramics were achieved remarkable development in ceramic knee replacements, a field pioneered by Japanese researchers, because the behavior of these materials allow the production of devices similar in size to the metallic ones. In dentistry, a number of manufacturers are marketing metal-free dental implants, as well as machinable zirconia blanks for the production of crowns, bridges, copings by CAD/CAM. Besides oxides, that in todays’ orthopedics and dentistry are the state-of-the-art bioinert ceramics, silicon nitride has found application in spinal surgery, and investigations in view of its use in joint replacement bearings are in progress.

Abstract: An important breakthrough of orthopedic surgery is to use bone cement to fill the space between an artificial joint and bone tissue, which allows the artificial joint to stabilize on human bone tissues. However, surgery failure cases due to bone cement utilization and side effects still exist at present. Therefore, the purpose of this study is to investigate bone cement characteristics, such as coagulation time, consolidation time, maximal exothermic temperature and anti-compressive strength, etc. under different mixture ratios. Our results showed that the smaller the ratio of polymethyl methacrylate and methyl methacrylate (PMMA/MMA), the lower exothermic temperature and the stronger anti-compressive resistance. These results are helpful to reduce incidences of post surgery side effects. Of note, bone cement supplement decreases corresponding to loading and operating time, which will become a major challenge for orthopedic surgery.

Abstract: Electrohydrodynamic (EHD) dispersion of macromolecular components in a biological bearing consisting of a poorly conducting synovial fluid both in the cavity of the bones and in the bounding porous cartilage of finite thickness is investigated using Taylor’s [4] dispersion model . It is shown that artificial joints involving smart materials of nanostructure discussed here work more efficiently than the natural joints.

Abstract: Wear is the primary cause of failure of joint replacement prostheses. In this paper, the Ultra High Molecular Weight Polyethylene (UHMWPE) as an artificial joint acetabular material was reinforce by nano-ZrO2 particles. The friction and wear properties of ZrO2 - UHMWPE composites sliding against the Co-Cr-Mo alloy were studied under lubrication of distilled water, saline and calf serum. The worn surface is observed by the optics microscope to examine the wear mechanism of the composite. The hardness and wetting angle of the composites were also measured. The result shows that the hardness, wettability, friction and wear resistance were all improved by filing with nano-ZrO2 particles. The 2%ZrO2 - UHMWPE composite had the lowest wear rate.

Abstract: Wear is the primary cause of the failure of joint replacement prostheses. In this paper, the ultra-high molecular weight polyethylene (UHMWPE) as an artificial joint acetabular material was filled with nano-powder of SiO2 of various mass fractions. The effect of SiO2 mass fraction on the tensile strength, tensile modulus, wetting property and tribological properties of the SiO2-UHMWPE composites were investigated when sliding against Ti-6Al-4V under lubrication of physiological saline water. The morphologies of the worn surfaces of composites were observed with optical microscope. As a result, the tensile strength, tensile modulus, wettability and wear resistance of the composites were all improved by filling with SiO2, and the composites had largely decreased friction coefficients under lubrication of physiological saline water compared with the unfilled UHMWPE. This was attributed to the reinforcing function of the nano-powder of SiO2 in the composites and the lubricating action of the water boundary film. The wear of pure UHMWPE was dominated by plowing, plastic deformation, while the SiO2-UHMWPE was characterized the mild fatigue wear.