Porous titanium-coated polyetheretherketone implants exhibit an improved bone–implant interface: an in vitro and in vivo biochemical, biomechanical, and histological study

Abstract

Purpose

Spinal interbody fusion cages are designed to provide immediate stabilization for adjoining vertebrae and ideally enable bony ingrowth to achieve successful integration. For such an implant, cells must be able to attach, move, grow, and differentiate on its surface. These cellular interactions are dependent on how the implant surface enables the coating and binding of blood and tissue fluid proteins that support cell adhesion. The purpose of this study was to evaluate the in vitro and in vivo osteoblast cell–implant surface interactions that result in osseointegration onto a surface composed of plasma-sprayed titanium on a polyetheretherketone (PEEK) substrate or titanium-coated PEEK (Ti-PEEK) (Plasmapore^XP®) as compared to uncoated PEEK implants.

Materials and methods

The influence of the Ti-PEEK surface modification on the biochemical, biomechanical, and histological properties at the bone–implant interface is demonstrated both in vitro using simulated bone-forming cell culture experiments and in vivo using a 12- and 24-week ovine implant model.

Results

Osteoblast-like cells attached to the Ti-PEEK surface upregulated early bone-forming activity as measured by an increase in transcription and translation of ALP and BMP-2 when compared to cells on PEEK. Similarly, a significant increase in new bone formation, bony apposition, and pullout strength was demonstrated on Ti-PEEK implants when compared to PEEK implants at 12 and 24 weeks in an ovine implant in vivo model.

Conclusion

The study shows that the Ti-PEEK surface demonstrated enhanced osseointegrative properties compared to PEEK both in vitro and in vivo.

Keywords:

• porous titanium
• implant coating
• osteoblast differentiation
• osseointegration
• pullout test
• sheep

Acknowledgments

This study was funded by Aesculap Implant Systems, LLC, and Aesculap Biologics, LLC. The authors wish to thank Dr Harold M Aberman for assistance in the in vivo study design and surgical procedure, Professor Himanshu Jain and Professor Mathias Falk of Lehigh University for performing the SEM analysis, and Stefan Schmiedberg for assistance with the statistical analysis.

Disclosure

RCS, CAW, and NW are paid employees of Aesculap Implant Systems, LLC, and Aesculap Biologics, LLC. BCC is a paid consultant of Aesculap Implant Systems, LLC. The other authors report no conflicts of interest in this work.