Orthopedic bearings

Kyomoto M, Moro T, Yamane S, Hashimoto M, Takatori Y, Ishihara K. Poly(ether-ether-ketone) orthopedic bearing surface modified by self-initiated surface grafting of poly(2-methacryloyloxyethyl phosphorylcholine). Biomaterials 2013 34(32) 7829- 39. 

The second part of the Handbook is focused on the use of UHMWPE as an ortiiopedic biomaterial. Chapter 4 reviews tire clinical origins of UHMWPE in hip replacement, which was introduced to orthopedics in 1962 by Sir John Chamley. Although several variants of UHMWPE have been investigated since the 1960s, UHMWPE remains the gold standard orthopedic bearing material still widely used today in joint replacements around the world. Chapter 5... 

Since the recall, zirconia has fallen out of favor as a bulk orthopedic bearing biomaterial. However, zirconia continues... 

In the 1970s, carbon fiber-reinforced (CFR) UHMWPE composites were considered for orthopedic implants and were even commercially introduced (Poly 11, Zimmer, Inc., Warsaw, Indiana, USA). However, catastrophic short-term clinical failures [2, 3] eventually led to the abandonment of Poly 11 and the perception for decades, among surgeons and researchers alike, that UHMWPE composite materials may not be appropriate for orthopedic bearing applications. Today, with the interest in UHMWPE development that was stimulated by radiation and thermal processing techniques, as well as the growing use of UHMWPE composites in nonmedical arenas, there is renewed curiosity about these materials for biomedical applications. 

Although self-reinforced UHMWPE was effectively abandoned for orthopedic bearings, interest has continued in other UHMWPE matrix composites, driven partly by new initiatives in nanocomposites materials science and polymer science. Indeed, UHMWPE matrix composites have been employed industrially for decades, and researchers have continued to explore the effect of historical standard fillers on the mechanical and dielectric properties of UHMWPE [36—40]. Solid lubricants, such as glass, graphite, ceramics (e.g., kaolin, AI2O3), and molybdenum... 

UHMWPE composite research for orthopedic bearings has also recently expanded to include mineral and quasi-crystaUine fillers [47]. Xie and colleagues have evaluated chemically crosslinked UHMWPE filled with micron-sized quartz particles [47]. Anderson et al. [48] have studied blends of Al-Cu-Fe powders and UHMWPE for orthopedic applications. These new composite UHMWPE bearing materials are still in the early phases of experimental investigation. 

Improvement in wear is frequently cited as a motivation for current composite research in UHMWPE for orthopedic implants [43, 44, 47—51]. Thus far, the use of fillers alone has not proven effective in reducing the wear rate of UHMWPE by an order of magnitude, as has been observed with extensive radiation crossfinking. Whereas conventional UHMWPE may have been the state of the art when early research on UHMWPE composites was initiated, today UHMWPE matrix composites need to demonstrate superior properties when compared with unfilled radiation crosshnked materials. Because the tribology of UHMWPE in artificial joints is strongly dependent on the kinematics and lubricant, additional research is needed to fuUy characterize the biotribological behavior of UHMWPE micro- and nanocomposites for specific orthopedic bearing applications. 

Calcium and Phosphate Salts Bloactive Glass Granules Bloactive Glass-Ceramic Granules Orthopedic Load-Bearing Applications... 

Recently, polyphase acrylic polymers have become increasingly important. They are the preferred materials for restoring anterior teeth where esthetic considerations are paramount. However, they are not satisfactory for the restoration of posterior teeth, especially in load-bearing locations where mechanical properties, such as abrasion resistance, are important (7). These materials are also used to make hip prostheses, and they are finding increasing application in orthopedics (8). 

Hulbert S.F. and Klawitter J.J. 1971. Application of porous ceramics for the development of load-bearing internal orthopedic applications. Biomed. Mater. Symp. pp. 161 229. 

The metals commonly used in medical devices are stainless steel (Types 316 and 316 L), cobalt-chromium-based alloys, titanium, and titanium-based alloys. Metals are used extensively in orthopedic surgery for load-bearing devices, such as artificial joints and fixation devices (wires, pins, screws fracture plates, etc.). Other metals include tantalum, gold, and mercury alloys the latter two are used predominantly in dentistry. 

Ceramics, such as the coinmonly used Alumina (AI2O3) and Zirconia (Zr02), tend to have a very high elastic modulus (around 400 GPa), have a low coefficient of friction, and are resistant to wear. These properties make them useful as the load-bearing surfaces in orthopedic implants. 

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