Coating of carbon fiber‐reinforced polyetheretherketone implants with titanium to improve bone apposition

Abstract

Carbon fiber-reinforced polyetheretherketone (CF/PEEK) is a thermoplastic composite biomaterial exhibiting properties suitable for load-bearing orthopedic implants. However, the hydrophobic surface of CF/PEEK implants induces the deposition of a peri-implant fibrous tissue capsule preventing bone apposition. However, if bone apposition was improved, the use of CF/PEEK in orthopedics could be increased as it has many advantages compared with metallic implants. In this study, CF/PEEK screws were coated with titanium (Ti) using two different techniques, namely vacuum plasma spraying (VPS) and physical vapor deposition (PVD) with uncoated screws as controls. These coatings were characterized and implanted in a loaded sheep tibia model. In the characterization of the screw surfaces using microscopy techniques, the uncoated screws were seen to have an irregular surface. The PVD coating appeared smooth and consistent, whereas the VPS coating appeared to be a rough coating with some inhomogeneities, which did not cover the entire surface area. Nevertheless, in the ex vivo analysis the VPS-coated screws had a screw removal torque which was statistically greater than uncoated and PVD-coated screws (p ≤ 0.002 for both comparisons). Additionally, the VPS-coated screws had a statistically higher bone contact area than the uncoated screws (p = 0.006), whereas no statistical difference was detected between VPS and PVD coating types (p = 0.11). Thereby illustrating that Ti coating of CF/PEEK screws significantly improve bone apposition and removal torque compared with uncoated CF/PEEK screws.

Do Surface Porosity and Pore Size Influence Mechanical Properties and Cellular Response to PEEK?

“…Interest in improving PEEK's osseointegration has accelerated in recent years after numerous reports have described its inability in smooth form to facilitate bone apposition [9,23,25,34,51]. Reasons why this interest persists (as opposed to abandoning PEEK altogether) are often attributed to the other qualities of PEEK that make it favorable in orthopaedic and spinal applications, mainly its radiolucency, MRI compatibility, high strength, and fatigue resistance.…”

“…However, attributable in part to PEEK's relatively inert and hydrophobic surface, recent evidence has demonstrated that smooth PEEK can exhibit poor osseointegration [9,25] and fibrous capsule formation around the implant [23,34]. Lack of bone-implant contact can induce micromotion and inflammation that leads to fibrous layer thickening, osteolysis, and implant loosening [2,13,29,37,48].…”

Effect of surface roughness on osteogenesis in vitro and osseointegration in vivo of carbon fiber-reinforced polyetheretherketone–nanohydroxyapatite composite

“…8,9 Besides its excellent mechanical properties, CFRPEEK inherits the nontoxicity, good chemical resistance, natural radiolucency, and even magnetic resonance imaging compatibility from PEEK. 8,10,11 However, although the materials have attracted much attention as orthopedic/dental implants since the 1980s, the bioinertness of CFRPEEK impedes osseointegration after implantation, thereby severely hampering clinical adoption. 8,9,12 The integration of implants with the surrounding bone, a process termed osseointegration, is critical for successful bone regeneration and healing in dental and orthopedic applications.…”

CHAPTER 7. Interfaces in Composite Materials

“…13 Furthermore, polyether ether ketones (PEEK), which have become a polymer of choice for fixation of hard tissue, primarily in spinal applications, has been combined with hydroxyapatite, carbon fillers and fibers to enhance the material integration within the body. [14][15][16][17][18] The use of some fillers (e.g., carbon fibers) reinforces the material, thus allowing the fabrication of even stronger devices for load bearing applications. 19 …”