Fabrication Method And Property Analysis And Biological Evaluation Of Surface Porous Polyether Ether Ketone

PEEK possesses a series of good biological properties such as excellent corrosion resistance,appropriate mechanical property compared to natural bone and good radiolucency,which made PEEK the preferred material for bone implantation.However,PEEK has properties of biological inertness and hydrophobicity.Those properties would prevent surrounding tissues to bond with PEEK after implantation and are adverse to PEEK-tissue interface fixation.One way to improve biocompatibility of PEEK is to modify PEEK into porous structure,so that neighbors could grow into the holes to enhance fixation.For bulk porous PEEK,there would be a great reduction of strength.When applied for high load-bearing surroundings like joint and spine area,it could not meet mechanics requirement.Therefore,for the purpose of promoting bone integration and maintaining strength necessary for load-bearing condition,an attempt to modify PEEK into a surface porous structure has been made in this study.Porous structure with certain porosities and aperture ratio can not be obtained by common methods-sintering and salt extraction.In this paper,SP-PEEK with certain porosities and 100% open pores was fabricated by die casting and etching process.Titanium wire was used as pore-making agent and was fabricated into entangled porous plate which was filled with molten PEEK later.When cooling to room temperature,titanium wire was etched to obtain SP-PEEK.Effects of porosities,pore sizes and porous layer proportions on macro and micro morphology,uni-axial compressive properties of SP-PEEK respectively were studied in this paper.In addition,the wear resistance of PEEK was compared with that of titanium under simulated body fluid environment.SP-PEEK was evaluated in vitro as well.Pores in SP-PEEK stayed the shapes of prepared porous titanium plates.With the increase of porosity and the decrease of pore size,the denser the pore distribution is.It has nothing to do with pore layer proportion.pores are point-like,rod-like and arc-shaped.Pores in transverse section were more arc-shaped.In longitudinal section,pores were more point-like.Average wall thickness both in transverse section and in longitudinal section got smaller with the increase of porosity and decrease of pore size.Due to the anisotropy of SP-PEEK,the effects of porosities,pore sizes and porous layer proportions on uni-axial compressive properties of SP-PEEK were studied under transverse and axial forces respectively.Stress-strain curves of SP-PEEK revealed similar tendencies.Those curves included three deformation regions: linear elasticity,yielding terrace and densification.Obvious yield points and platform stages were revealed in curves under transverse force.Whereas curves under axial force did not reveal distinct yield points and yield platforms.For SP-PEEK with porosities of 30-50%,yield strengths and elastic moduli under transverse force were 54.9-57 MPa and 5.9-9.2 GPa respectively;yield strengths and elastic moduli under axial force were40.5-49.8 MPa and 5.2-5.4 GPa respectively.With the increase of porosity,both yield strength and elastic modulus were decreasing.For SP-PEEK with pore sizes of 270 μm and 400 μm,yield strengths and elastic moduli under transverse force were 46.7MPa and 55.8 MPa,6.47 GPa and 7.9 GPa respectively;yield strengths and elastic moduli under axial force were 47.7 MPa and 48.3 MPa,4 GPa and 5.3 GPa respectively.For SP-PEEK with porous layer proportions of 10-20%,yield strengths and elastic moduli under transverse force were 38.5-60.4 MPa and 6.3-9.3GPa respectively;yield strengths and elastic moduli under axial force were 37-56.1 MPa and 4.6-6.5 GPa respectively.Both yield strength and elastic modulus decreased with the increase of porous layer proportion.Elastic moduli of SP-PEEK were comparable with that of natural bone(0.01-28 GPa),suggesting that SP-PEEK could serve under both load-bearing and non-load-bearing condition.The friction test of PEEK under simulated body fluid environmentshowed that wear resistance of PEEK was better than that of titanium.In vitro tests showed that there is no significant difference in cell survival,cell proliferation and differentiation between MG63 cells cultured in SP-PEEK leaching medium and cells in DMEM,suggesting that the raw materials and fabrication methods did not cause toxicity.Adhesion test showed that MG63 cells spread well and were tightly adhered to pore surfaces,which meant that cells could grow into pores in surface layer and porous layer of SP-PEEK could help fixation between implants and adjacent tissues after implantation.