The Effect of Titanium Nitride Coatings on the Ingrowth and Interface Strength of Three-Dimensional Printed Porous Implants.

Background: The impact of titanium nitride (TiN) coatings on biologic fixation of modern titanium-based porous surfaces fabricated using additive manufacturing (AM) techniques remains unexplored. This study aimed to compare the biological fixation of three-dimensional (3D)-printed porous implants, with and without TiN coating, in a canine model.

Methods: A canine femoral transcortical model was used to evaluate the characteristics of bone ingrowth of fully porous Ti-6Al-4V cylindrical implants fabricated using either laser rapid manufacturing or electron beam melting. Implants were further divided into coated (TiN) and uncoated groups. Histological (bone ingrowth evaluation via scanning electron microscopy) and mechanical push-out testing on the four groups of implants were performed at 4 and 12 weeks postimplantation.

Results: Both TiN-coated and uncoated implants demonstrated substantial bone ingrowth at both time points. Bone ingrowth ranged from 35 to 50% at 4 weeks and then increased to 49 to 59% at 12 weeks. Mechanical tests indicated shear fixation strength ranging from 18 to 20 MPa at 4 weeks, increasing to 34 to 38 MPa at 12 weeks. There was no significant difference in either the amount of bone ingrowth or shear strength between TiN-coated and uncoated implants at either time point for both the laser rapid manufacturing and electron beam melting implants.

Conclusions: This study demonstrated substantial bone ingrowth as well as comparable shear strength between TiN-coated and uncoated implants, regardless of manufacturing technique. Titanium nitride coatings do not influence biological fixation on modern titanium-based AM porous surfaces.