The development of new titanium arc-sprayed artificial joints

The authors developed the new method of titanium porous coating onto Ti-6Al-4V and the coating layers and the substrates were evaluated in this study. The new method is inert gas-shielded arc spraying (ISAS), operated in an inert gas stream at atmospheric pressure, and the coatings showed far fewer voids and cracks in the layers and interfacial areas between the layer and the substrate compared with low-pressure plasma spray (LPPS) coatings commercially available currently. Wear of ISAS coatings by the blast erosion test was one sixth that of LPPS coatings, so the bonding strength between titanium porous particles is six times higher for ISAS coatings than for LPPS. mperature of the heat treatment after ISAS coating process is 650 °C, which is below the beta transus and far lower than that of beads or wire mesh coatings, and the fatigue strength of the substrates is 38.2% relative to uncoated materials. Chemical analysis and X-ray diffraction analysis revealed that very few titanium reactants with oxygen and nitrogen were produced during the ISAS coating process. w method of HA flame spray coating onto the surface of the ISAS coating (HA/ISAS) was also developed in this study. Animal experiments showed that the interfacial shear strength with surrounding bone was higher for the ISAS and HA/ISAS coatings than for the control smooth surface. From the histological findings, sound new bone formation was recognized around the HA/ISAS coatings at an early stage compared with ISAS coatings. The results indicate that ISAS and HA/ISAS coatings can be successfully used clinically for cementless joint replacements, and HA/ISAS coatings are expected to contribute more satisfactory clinical results in the long term.