Porous PEEK improves the bone-implant interface compared to plasma-sprayed titanium coating on PEEK

Area of Science:

• Biomaterials Science
• Orthopaedic Surgery
• Tissue Engineering

Background:

• Polyether-ether-ketone (PEEK) is widely used for load-bearing orthopaedic devices due to its radiolucency and mechanical properties.
• Smooth PEEK surfaces can result in fibrous encapsulation and suboptimal osseointegration.
• Investigating surface modifications is crucial for enhancing PEEK implant performance.

Purpose of the Study:

• To compare the in vitro and in vivo bone response to porous PEEK and plasma-sprayed titanium (Ti)-coated PEEK.
• To evaluate the effect of surface topography on osseointegration and implant fixation.
• To determine if PEEK topography influences fibrous encapsulation.

Main Methods:

• MC3T3 cells cultured on smooth PEEK, porous PEEK, and Ti-coated PEEK for in vitro assays (calcium, osteocalcin, VEGF, ALP).
• Cylindrical implants (smooth PEEK, porous PEEK, Ti-coated PEEK) surgically placed in rat tibiae for 8 weeks.
• In vivo analysis included micro-computed tomography (μCT), histology, and pullout testing.

Main Results:

• Porous PEEK surfaces showed increased cellular calcium, osteocalcin, and VEGF production compared to smooth and Ti-coated PEEK.
• Bone ingrowth into porous PEEK was substantial and correlated well between μCT and histology.
• Porous PEEK implants achieved higher pullout force, stiffness, and energy-to-failure, indicating superior mechanical interlocking.

Conclusions:

• Porous PEEK surfaces promote enhanced osteogenic differentiation in vitro and improved implant fixation in vivo.
• Surface topography, specifically porosity, plays a critical role in determining osseointegration and mechanical interlocking.
• These findings suggest that modified PEEK surfaces can overcome limitations associated with smooth PEEK implants.