Polyether ether ketone (PEEK) is a three-dimensional (3D)-printable material with excellent mechanical properties for bone replacement implants. However, bioactivation is needed to improve its osseointegration. Plasma immersion ion implantation (PIII) provides PEEK surfaces with a high density of radicals, improving hydrophilicity and enabling covalent bonds with biological molecules. On the PIII-treated surface, amorphous calcium phosphate-associated protein depositions form a strongly bonded, mineralised layer during incubation in a cell culture medium. The strong adhesion is attributed to covalent linking of protein to the PEEK surface, which cannot be achieved by improved hydrophilicity or the introduction of functional groups alone. After 3D-printed porous PEEK scaffolds were PIII-treated, osteoblast-like cell attachment increased by 8.8%, proliferation rate increased by 27% and mineralisation was enhanced, encouraging rapid osseointegration of patient-specific implants.

Adhesion of regenerating bone tissue to orthopaedic implants is critical to their long‐term success. Titanium has excess rigidity, interferes with imaging, and complicates radiation treatment. Poly(ether‐ether‐ketone) (PEEK) is a preferred material, but is limited by biological inertness. We show that plasma immersion ion implantation (PIII) imparts osteoadhesion on 3D printed PEEK using in vitro pull‐off tests and in vivo torque tests in a sheep scapula model. PIII‐PEEK prints incubated with bone cells in vitro show 9–14 times higher pull‐off strength, compared to untreated implants. Treated implants in vivo require seven times higher torque for release from the sheep scapula. We propose PIII‐PEEK as a scaffold material with tensile properties analogous to collagen, the fibrillar component of bone, to produce fracture‐tough fully integrating scaffolds.

Bone diseases such as osteosarcoma often require aggressive removal of bony tissue. [1] After surgery, bone function is restored by the hemostatic stimulation of the local bone to fill the defect. [2] In critical-sized defects, this mechanism is insufficient to fill bone loss and reconstruction using a bone graft from another part of the skeleton or a prosthetic bone implant is needed. [3,4] Titanium plates have been used to bridge bone segments but because of the differences in elastic modulus, implant failure from stress-shielding osteolysis may ultimately occur. [5][6][7] For cancer patients requiring radiation therapy, titanium causes unwanted shielding and scattering of the radiation, compromising treatment quality. [5,[8][9][10] Poly-ether-etherketone (PEEK) is a thermoplastic polymer, with biomechanical properties similar to those of bone, and has been proposed as an alternative to titanium for implants, causing less interference for both imaging