High-strength, surface-porous polyether-ether-ketone for load-bearing orthopedic implants

Despite its widespread clinical use in load-bearing orthopedic implants, polyether-ether-ketone (PEEK) is often associated with poor osseointegration. In this study, a surface-porous PEEK material (PEEK-SP) was created using a melt extrusion technique. The porous layer was 399.6 +/- 63.3 lam thick and possessed a mean pore size of 279.9 +/- 31.6 mu m. strut spacing of 186.8 +/- 55.5 mu m, porosity of 67.3 +/- 3.1% and interconnectivity of 99.9 +/- 0.1%. Monotonic tensile tests showed that PEEK-SP preserved 73.9% of the strength (71.06 +/- 2.17 MPa) and 73.4% of the elastic modulus (2.45 +/- 0.31 GPa) of as-received, injection-molded PEEK. PEEK-SP further demonstrated a fatigue strength of 60.0 MPa at one million cycles, preserving 73.4% of the fatigue resistance of injection-molded PEEK. Interfacial shear testing showed the pore layer shear strength to be 23.96 +/- 2.26 MPa. An osseointegration model in the rat revealed substantial bone formation within the pore layer at 6 and 12 weeks via microcomputed tomography and histological evaluation. Ingrown bone was more closely apposed to the pore wall and fibrous tissue growth was reduced in PEEK-SP when compared to non-porous PEEK controls. These results indicate that PEEK-SP could provide improved osseointegration while maintaining the structural integrity necessary for load-bearing orthopedic applications. (C) 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.