Alkali- and heat-treated porous titanium for orthopedic implants

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Abstract
This study was carried out to investigate the effects of the alkali and heat treatments on the bone-bonding behavior of porous titanium implants. Porous titanium implants had a 4.6 mm solid core and a 0.7 mm thick porous outer layer using pure titanium plasma-spray technique. Three types of porous implants were prepared from these pieces: 1. control implant (CL implant) as manufactured 2. AW-glass ceramic bottom-coated implant (AW implant) in which AW-glass ceramic was coated on only the bottom of the pore of the implant 3. alkali- and heat-treated implant (AH implant), where implants were immersed in 5 mol/L NaOH solution at 60°C for 24 h and subsequently heated at 600°C for 1 h. The implants were inserted into bilateral femora of six dogs hemi-transcortically in a randomized manner. At 4 weeks, push-out tests revealed that the mean shear strengths of the CL, AW, and AH implants were about 10.8, 12.7, and 15.0 MPa, respectively. At 12 weeks there was no significant difference between the bonding strengths of the three types of the porous implants (16.0–16.7 MPa). Histologically and histomorphologically, direct bone contact with the implant surface was significantly higher in the AH implants than the CL and AW implants both at 4 and 12 weeks. Thus, the higher bonding strength between bone and alkali- and heat-treated titanium implants was attributed to the direct bonding between bone and titanium surface. In conclusion, alkali and heat treatments can provide porous titanium implants with earlier stable fixation. © 2000 John Wiley & Sons, Inc. J Biomed Mater Res 54: 198–208, 2001