Abstract
Polyetheretherketone (PEEK) is a thermoplastic polymer that is predominant in spinal surgery as the material of choice for spinal fusion cages, and is also used for bone anchors, cruciate ligament interference screws, and femoral stems. It has the distinct advantage of having similar mechanical properties to bone, but its clinical application as implant material is limited by a lack of bioactivity. This project aims to create an PEEK surface capable of osseointegration using a surface modification technique known as oxygen plasma treatment.
PEEK surfaces were injection molded, washed and then treated in a plasma chamber for up to 10 min. Surfaces were characterised using atomic force microscopy (AFM), scanning electron microscopy (SEM), water contact angle measurements and X-ray photo-electron spectroscopy (XPS). Human bone marrow cells were cultured on the surfaces and assessed for calcium production (using alizarin red stain).
Water contact angle measurements show that after plasma treatment, the surfaces become very hydrophilic, before developing a meta-stable state at approx. 6 weeks. AFM and SEM showed destruction of the nano-pits at treatment durations longer than 2 mins. XPS detected a progressive increase in the atomic proportion of oxygen at the surface with increasing plasma treatment duration. There was significantly less alizarin uptake (and hence calcium production) on the untreated PEEK compared to the plasma treated PEEK surfaces (p < 0.05).
These results show that oxygen-plasma treatment can increase calcium production on PEEK surfaces and may improve long term osseointegration of PEEK implants.
