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Each year approximately 50000 hip replacement operations are preformed in the UK, and 600000 are preformed globally. There are many designs of hip replacements available to the surgeon, the surgeon will select the one, which he believes is the best or has been trained to use. The design of the artificial hip must take into account the hip joint forces, mechanical strength, ease of implantation and fit, wear and durability, chemical composition, bio-compatibility and materials selection. The materials selection is very important because previous design considerations such as biocompatibility, wear and durability depend upon it. ... 1 shows the stiffness (Young’s modulus), strength and fracture resistance of a number of materials used for implants. At present we do not have any materials that can imitate perfectly the mechanical property of bone. ... Ceramics (alumina, hydroxyapatite-HA) are generally very hard materials; they are strong in compression but display low fracture resistance. ... 1 Young’s Modulus, strength and fracture resistance of different materials
There are two major types of artificial hip joint, cemented prosthesis (the artificial implant inserted into the body) and cementless prosthesis. ... Then the acetabulum (or hip socket) is removed and replaced with a metal shell and a plastic or ceramic liner.
Sir John Charnley developed the standard for the hip replacement system, and even today all most all-current prosthesis are variations of his original design. The English Surgeon was able to develop his ideas by analysing his work on animal joint lubrication. ... He first used Teflon (trade name for polytetraflouroethene PTFE) shells on the surface of the femoral. ... This socket was used with a highly polished stainless steel ball. In the past three decades the majority of hip prosthesis implants have included an acetabulur cup of ultra high molecular weight polyethylene articulating against a femoral ball of cobolt-chromium alloy, and this is still the case in 90% of all cases today.
The cobolt chromium alloy (also known as Vitallium)(27-30% Cr, 5-7% Mo, rest Co) is used because it is a tough metal able to withstand the weight bearing demands of the hip joint.
Approximate Word count = 1641
Approximate Pages = 6.6
(250 words per page double spaced)
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