In-vivo study of the osseointegration of cemented and cementless porous 3D printed implants

Orthopedic implant fixation type, whether cemented (using PMMA bone cement) or cementless (direct implant-bone contact without bone cement), dictates immediate and long-term implant stability. However, despite the two common clinical fixation practices, previous in-vivo studies have not studied or quantified the osseointegration strength of cemented and cementless approaches. As cementless porous implant topographies become more prevalent in orthopedic devices through 3D-printing, an understanding of how implant interface strength differs between the two fixation types is crucial. This study employed an established ovine bicortical defect model to compare osseointegration strength among solid and surface porous 3D-printed implant materials with and without the application of bone cement. Cementless implants exhibited at least 50% higher fixation strength than cemented implants with the same surface topography. Further comparison between cementless surface and bulk porous implants demonstrated weaker osseointegration strength in 80% highly bulk porous implants than the 60% bulk porous implants. These results highlight the need to balance porosity with implant structure. Pre-cemented implants and implants cemented in-vivo had the same low fixation strength indicating that the in-vivo curing process had no meaningful effect on fixation strength. The results identify fundamental trends in implant fixation method, osseointegration, and porosity that can help inform future orthopedic implant design and surgical decision-making.