Introduction: Interbody fusion devices are commonly made from polyetheretherketone (PEEK), but smooth PEEK devices are associated with poor osseointegration. PEEK devices have been coated with titanium to improve surface osseointegration, but such coatings risk delamination when the devices are subjected to shear forces during impaction into an interbody space. The present study sought to evaluate the durability and osseointegration of a novel porous PEEK (pPEEK) implant in comparison to a plasma-sprayed titanium coated PEEK (TiPEEK) implant.
Methods: To evaluate durability, pPEEK and TiPEEK devices were impacted between polyurethane foam blocks to simulate insertion into an interbody space under shear loading conditions (n=6). Before and after impaction, pPEEK cages were evaluated by µCT and TiPEEK cages were imaged via SEM and EDS. Next, pPEEK (n=4) and TiPEEK (n=3) cylindrical implants were implanted into a rat tibial defect model. At 8 weeks, animals were euthanized and extracted bone-implant constructs were subjected to µCT scanning and biomechanical testing to evaluate the interfacial strength.
Results: Impaction testing revealed that pPEEK cages experienced no significant change in porosity and a 2.2% decrease in pore size (p<0.01) before and after impaction (Figure 1). TiPEEK cages displayed visual macroscopic damage with a 28.5% decrease in Ti-coating area coverage and significant decrease in surface roughness (from 8.16±1.54µm to 5.74±1.37µm). After 8 weeks post-implantation in the rat model, a thin layer of mineralized tissue was observed on micro-CT near and within the porous architecture of pPEEK implants (Figure 2). pPEEK implants exhibited significantly greater pullout failure loads (36.8±2.8N) compared with TiPEEK implants (21.1±1.1N) (ANOVA, Tukey’s test, p<0.05).
Conclusions: The pPEEK implants exhibited the ability to withstand forces associated with interbody insertion as well as improved bone-to-implant fixation via ingrowth into the porous architecture. These results suggest pPEEK implants could be a superior option for fusion surgery compared with Ti-coated PEEK devices.
Patient Care: Porous PEEK interbody implants have the potential to increase bony ingrowth into the devices, thus enhancing fixation/fusion and improving patient outcomes while maintaining radiolucency so that fusion can be assessed radiographically.
Learning Objectives: By the conclusion of this session, participants should be able to: 1)Describe the differences between porous PEEK and Ti-coated PEEK implants regarding resistance to interbody insertion shear forces 2)Understand the ability of porous PEEK implants to resist displacement due to osseointegration, 3)Discuss the reasons porous PEEK implants may be preferable to smooth or Ti-coated PEEK implants as interbody fusion devices.