Knee joint replacement

HDPE by itself is a safe plastic material on account of its chemical inertness and lack of toxicity. Consequently, film and containers made from HDPE are used on a large scale in food and dmg packaging. Moreover, HDPE has been used in prosthetic devices including hip and knee joint replacements (122). 

The doctor confirms that Mr Jones is in quite severe pain as he has had recent orthopaedic surgery (knee joint replacement) and therefore she feels the intention of the prescriber would be the 50 mg tds, giving an opportunity to reduce the dose to 25 mg if it is not well tolerated. You confirm that she requires 50 mg tds and arrange to send the prescription to the surgery to be amended. 

A knee joint simulator was designed and built in the bioengineering laboratory at Leeds in the late 1970 s to enable the mechanical and tribological characteristics of current and projected knee joint replacements tp.he assessed. The simulator has been described by Dowson et al and it is shown in Figure 1. Realistic load and motion cycles are applied to the knee joints to simulate any desired activity, but usually walking, and the penetration of the metallic femoral components into the polymeric tibial components after a large number of cycles can then be used to assess the life of the joints. Furthermore, the penetrations recorded, which include both wear and creep, can be related to results of laboratory wear studies of the behaviour of UHMWPE and to the in-vivo performance of total replacement knee joints. The simulator is therefore an Important machine in both the pragmatic and fundamental aspects of total replacement knee join development. 

The prosthesis for total knee joint replacement consists of femoral, tibial, and patellar components. Compared to the hip joint, the knee joint has a more complicated geometry and movement biomechanics, and it is not intrinsically stable. In a normal knee, the center of movement is controlled by the geometry of the ligaments. As the knee moves, the ligaments rotate on their bony attachments and the center of movement also moves. The eccentric movement of the knee helps distribute the load throughout the entire joint surface [Burstein and Wright, 1993]. 

Auger, D.D., Dowson, D. and Fisher, J. (1995) Cushion form bearings for total knee joint replacement Part 1 design, friction, and lubrication. Proc. Inst. Mech. Engrs, 209, 73-81. 

In the medical praxis, UHMWPE have been used successfully as one half of the bearing couple (against metallic alloys or ceramics) in total hip and total knee joint replacements crosslinked under irradiation [82]. Even y-irradiated UHMWPE at doses higher than 100 kGy presents the incipient ffacmre development [83], the alkyl macroradicals are involved in crosslinking and in a smaller proportion they promote oxidation [84, 85]. The prosthesis manufactures by the irradiation of UHMWPE have long durability, because the application of radiation treatment induces an increased crystallinity and promotes sterilization in the whole volume of material. 

Bones, and their joints, are sometimes damaged by accidents, disease, aging, etc. When hip and knee joints are damaged, patients sometimes feel severe pain, and have much difficulty in walking, since these joints must slide smoothly at least a few thousand times every day under a load over several times body weight. In such cases, the joints must be replaced with artificial ones. The present number of hip and knee joints replaced with artificial ones total about 100 000 in Japan, and 600 000 in the United States. 

Co-based surgical implant alloys (see Table 3.1-88 for compositions) are used to fabricate a variety of implant parts and devices. These are predominantly implants for hip and knee joint replacements, implants that fix bone fractures such as bone screws, staples, plates, support structures for heart valves, and dental implants. The mechanical properties (shown in Table 3.1-89) depend sensitively on the thermal and thermomechanical treatments of the materials. 

Sawyer G. Temperature modeling in a total knee joint replacement using patient specific kinematics. Tribol Lett 2003 16(4) 343-52. 

HPDE is generally inert and lacking in any toxicity, which accounts for its widespread use in food packaging. It is also used in prosthetic devices, in surgery, hip or knee joint replacements, etc. 

Total knee joint replacement External fixation system... 

Other studies, conversely, cast doubt on the ultimate viability of carbon-UHMWPE composite usage in hip and knee joint replacement, especially after clinical exposure. After longer-duration pin-on-disc studies using 25% graphite powder-filled UHMWPE, Rostoker and Galante reported that the short-term improvement in wear resistance appeared to be lost [17]. Sclippa and Piekarski... 

UHMWPE is used as an articulating surface in both hip and knee joint replacements. As an acetabular component in THR (total hip replacement), its annual wear rate was reported to be approximately 0.1 mm/ year or 80 mmVyear against a 32 mm diameter femoral head. Hall et al. [70], and Oonishi et al. [71]. It is approximately a 30-fold reduction in wear rate in comparison with a PTFE socket that was first introduced by... 

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