Polyetheretherketone (PEEK) is widely used in medical implants because of its high strength, radiolucency, and favorable cytocompatibility. However, it is often linked to fibrous tissue formation instead of osseointegration. In order to overcome this limitation, porous polymers enable bone ingrowth, but inherently lack mechanical properties necessary for orthopaedic applications. Herein, we describe the wear behavior of porous PEEK and a porous PEEK spine device under multiple loading scenarios. Porous PEEK (pPEEK) was made by extruding Zeniva® PEEK (Solvay) through the spacing of NaCl crystals, followed by leaching. The resulting porous architecture is 60-70% porous with a pore size of approximately 350 µm. The abrasion resistance of pPEEK was characterized according to ASTM-F1978 to determine mass loss. pPEEK devices were impacted with a 1lb falling weight between two rigid polyurethane foam blocks, which represent vertebral bodies. The foam blocks were loaded in a custom fixture with an attached pneumatic cylinder at a preload of 200 N. µCT was used to quantify changes in the porosity, pore depth, and pore size of the structure before and after each test method. The measured mass loss after abrasion was 39±18mg for the injection molded control and 27.6 ±12.3mg for the pPEEK samples. Comparing the 3D pore structure before and after abrasion revealed a slight densification of the pore network and flattening of the top pore architecture. No change in porosity or pore depth was found between abraded and nonabraded pPEEK samples. µCT showed no significant difference before and after impaction for porosity volume fraction or porous depth. There was a significant difference in pore size (242±3 vs 233±4µm), representing a 3.7% change. These results show that porous PEEK can withstand physiologically and clinically relevant loading conditions and still retain their porous architecture for bone ingrowth.

Microcomputed tomography study of the wear behavior of porous PEEK for spine devices

253rd National Meeting (2017)

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