Surface characterization and in vivo performance of plasma-sprayed hydroxyapatite-coated porous Ti6Al4V implants generated by electron beam melting

• The porous Ti6Al4V implant was prepared using the electron beam melting method.
• The HA coating deposited on the surface of the porous implants by plasma-spraying
• The porous implants were implanted into distal femur bone defects of sheep.
• Plasma-spraying HA improved bone formation and osteointegration of porous implants.

Porous titanium with high strength and a low elastic modulus has received attention as an excellent orthopedic implant; however, the fabrication and biological performance of porous implant both need to be improved. A porous Ti6Al4V implant (TI) was prepared using the electron beam melting method, and some samples underwent surface modification with a hydroxyapatite coating (HA-TI) by plasma-spraying. After characterization of their surfaces, the TI and HA-TI materials were implanted into distal femur bone defects of sheep, and bone formation and osteointegration were evaluated at 2 and 4 months post-implantation. A micro computed tomography analysis indicated that the porous Ti6Al4V implant with interconnected pores had a high porosity ~ 69 ± 5% and large pore size ~ 514 ± 35 μm. Scanning electron microscopy, energy dispersive spectrometry, and X-ray diffraction analyses revealed that the HA coating was successfully deposited on the exterior surface of the implants; the elemental composition of the internal surface of the HA-TI material included calcium and phosphorus, as well as titanium and aluminum. Confocal laser scanning microscopy revealed that the surface roughness of the HA-TI group was significantly higher than that of the TI group. Micro computed tomography and histological analyses indicated that the bone formation of the HA-TI group was superior to that of the TI group at both 2 and 4 months post-implantation. In the HA-TI group, the new bone contacted the coating of the implant directly, and no fibrous tissue or gaps were observed at the bone–implant interface. This study demonstrates that hydroxyapatite coating of porous Ti6Al4V implants by plasma-spraying is suitable to improve the bone formation and osteointegration capabilities. In addition, the results demonstrate that HA-coated porous Ti6Al4V implants generated by electron beam melting have excellent prospects in orthopedic applications.