Adhesion of bone cement to porous and nonporous 3D printed surfaces

Bone cement is an adhesive commonly used to bond orthopedic implants to bone during a surgical procedure. Total joint replacements such as total knee, hip, shoulder, or ankle arthroplasties have metal or polymer components that are commonly cemented. However, implant failures can occur via debonding at the implant-cement interface, suggesting sub-optimal adhesion of the cement to the implant. In parallel, the orthopedic implant industry is seeing a significant rise in additive manufacturing (AM), which enables the seamless integration of surface porosity enhanced osseointegration in cementless procedures. However, there is a lack of foundational data or understanding of how bone cement adheres to 3D printed surfaces as a function of varying topography. This study evaluates adhesion of cement to clinically relevant printed implant surfaces, porous topographies, and materials. Adhesion strength of cemented samples was tested in shear. Surface porous layers were compared to traditional implant surface finishes (blasted, machined, polished). The impact of 3D printed surface porosity size and depth was also investigated. Testing revealed that the adhesive strength of porous surfaces (26.3 ± 3.1 MPa) was more than double the adhesive strength of all non-porous surfaces (the highest being the as-printed surface with a strength of 11.3 ± 2.5 MPa). The study also demonstrated porosity and layer-depth dependent performance trade-offs, with the best performing group having a 2x2x2 mm³ unit cell size and 0.50 mm layer depth and a shear strength of 26.31 ± 3.10 MPa. These results provide a foundation for improving designs of emerging 3D printed orthopedic implants that can be both cemented and cementless.