Hydroxyapatite (HA) coatings are used to improve the adhesion of bone onto implanted devices. This approach increases the integrity and hence the lifetime of the implant. Several orthopaedic appliances (HA coated and macrotextured) were recovered from patients after revision surgery. The implants were cleaned and sterilised in ethanol or formaldehyde before being photographed and sectioned for analysis. X-ray diffraction indicated that the remaining coating was of high crystallinity. Micro textured areas such as ribbings and fenestrations subjected the coating to different modes of stress which has affected the coating. Adhesive failure was evident on implants attributed to dissolution of the amorphous phase at the interface. Observation of the microstructure with scanning electron microscopy showed that coating degradation begins at the surface where the coating is resorbed and continues along the substrate-coating interface thereby compromising interface strength. The microstructure and the dissolution of retrieved implants are discussed in relation to the general coating features in plasma sprayed HA coatings.

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