Micro-CT Analysis of Implanted Poly-Ether-Ether-Ketone Scaffolds: Plasma Immersion Ion Implantation Increases Osteoconduction

Abstract

Poly-ether-ether-ketone (PEEK) is a biocompatible, high-strength polymer with biomechanical properties similar to soft bone that has been proposed as an alternative to titanium for orthopedic implants. Herein, micro-CT imaging of a 3D printed PEEK scaffold treated with plasma immersion ion implantation (PIII) to assess the degree of osteoconduction relative to an identical untreated structure, by implantation in the scapula of sheep, is performed. To overcome the lack of contrast between soft tissue and PEEK, a customized apparatus and alignment technique is designed and constructed. Principal component analysis is used to accurately locate the boundaries of the implant in the 3D dataset, with respect to reference coordinates. It is found that, within the interior volume of the scaffold, the PIII treated PEEK contains bone that is both more dense and in higher amounts than for untreated PEEK. The untreated PEEK shows more bone immediately outside the boundaries of the scaffold, indicating a lower affinity of the untreated scaffold for in-diffusion of osteocytes and associated mineralization. The greater osteoconduction of the PIII treated scaffold is attributed to the improvement in hydrophilicity and the provision of protein covalent binding.