Orthopaedic hip implant
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The use of surface coatings in orthopaedic and dental implants has significantly improved the quality of human life.
Modern implants provide improved recovery times and lower implant rejection rates. Early implants were expensive, and often failed because the bonding between the implant and the bone, a process known as osteo-integration, was poor. Several designs have been formulated to date but many failed to achieve a strong enough bond. A solution involves coating the metal with a layer of hydroxyapatite (HA). Hydroxyapatite forms almost three-quarters of natural bone. Coating the metal first with HA gives a stronger metal-bone bond. Even with this improvement, one in five implants can still fail. One of the main reasons of failure is the residual stress developed at the metal-HA interface. Neutrons offer significant advantages to analyse this critical interface, enabling measurements to be made in-depth and non-destructively. This unique capability enables us to improve our understanding of how HA bonds to the metal and bone.
R Ahmed (Heriot-Watt University), AM Paradowska (STFC), M Fitzpatrick (Open University)
Research date: January 2010
Contact: Dr R Ahmed, R.Ahmed@hw.ac.uk
Further reading: R Ahmed et al., Mater Sci Forum 652 (2010) 309
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