Materials Used In Hip Joint Replacement
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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. The three main factors, which will influence the performance of biomaterials in the human body, are: biocompatibility, mechanical properties and degradation. The table in Fig.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. Metals (steel, Co-Cr-Mo, Ti-6Al-4V) have sufficient strength and fracture toughness but have relatively high stiffness, which can lead to weight shielding problems. Ceramics (alumina, hydroxyapatite-HA) are generally very hard materials; they are strong in compression but display low fracture resistance...