Additive manufacturing (AM) holds significant potential in transforming medical applications, with a particular focus on polyetheretherketone (PEEK) and its derivatives, collectively known as poly-aryl-ether-ketone (PAEK) materials. Advances in AM precision have paved the way for the successful 3D printing of high-performance thermoplastics like PEEK, offering new prospects in load-bearing medical applications. This systematic review comprehensively assesses recent scientific literature concerning the tribo-mechanical properties and bioactivity of additively manufactured PAEK materials, with a specific emphasis on PEEK, for load-bearing medical uses. Despite substantial research into AM of metallic biomaterials, knowledge gaps persist regarding AM processing parameters, structure-property relationships, biological behaviours, and implantation suitability of PAEKs. This review bridges these gaps by analysing existing literature on the tribo-mechanical properties and bioactivity of additively manufactured PAEK materials, providing valuable insights into their performance in load-bearing medical applications. Key aspects explored include printing conditions, strength limitations, and outcomes of in-vitro and in-vivo evaluations. Through this systematic review, we consolidate current knowledge, delivering essential information for researchers, clinicians, and manufacturers involved in advancing additively manufactured PAEK materials for load-bearing medical applications.

Polyetherketoneketone (PEKK) (60/40 TERE/ISO) is characterized by a lower processing temperature and a higher glass transition temperature (Tg) compared to polyetheretherketone (PEEK), making it a promising material for 3D printing. However, it remains in amorphous state post-printing due to its slow crystallization rate. In this study, isothermal annealing is conducted on 3D printed pseudo amorphous PEKK at various times and temperature. Thermal analysis techniques reveal that both annealing time and temperature play a pivotal role in enhancing crystallinity, with levels reaching up to 27% when annealed between the Tg and the melting temperature (Tm). However, thermal stability decreased as the annealing temperature approached Tm. X-ray diffraction studies demonstrate that annealing between Tg and Tm promotes the development of stable form II crystals, while annealing at higher temperatures encourages the formation of form I crystals. Furthermore, dynamic mechanical analysis indicated a 44% increase in mechanical stiffness following annealing, and compressive testing shows improved yield strength, comparable to that of other polyaryletherketone (PAEK) materials. These findings suggest that controlled annealing of 3D printed PEKK enables precise tailoring of its crystallinity and mechanical properties, making it adaptable for a wide range of applications, such as biomedical devices that require patient-specific customization.

Tribocorrosion studies have primarily focused on hard-on-hard articulations, with limited research on metal-on-polymer (MoP) configurations despite their clinical relevance. This study investigates the tribocorrosion behaviour of cobalt-chromium (CoCr) alloy against 3D-printed polyetheretherketone (PEEK), conventionally manufactured PEEK, and ultrahigh molecular weight polyethylene (UHMWPE), with UHMWPE as the reference material. Tests were conducted using a reciprocating tribometer under open circuit and potentiostatic conditions in phosphate buffered saline (PBS) and bovine calf serum, with in-situ electrochemical monitoring. The results demonstrated that the presence of serum significantly decreased the charge transfer of the CoCr surface, hence decreasing electrochemical degradation when compared to PBS lubrication. The manufacturing methods for PEEK resulted in different surface characteristics, leading to variations in tribocorrosion behaviour; however, polishing to achieve homogeneous roughness minimized these differences. Furthermore, CoCr exhibited significantly higher charge transfer when slid against all tested PEEKs compared with UHMWPE (at least two-fold higher), suggesting that a PEEK-CoCr tribocouple results in an increase of tribocorrosion and a greater potential for metal ion release than a UHMWPE-CoCr tribocouple.

Polyetheretherketone (PEEK) is a high-performance thermoplastic widely used in orthopaedic and biomedical applications due to its excellent mechanical properties, biocompatibility, and suitability for additive manufacturing. However, its relatively poor friction and wear resistance limits its use in long-term, load-bearing implants. This study investigates the effect of hexagonal boron nitride (hBN) and silicon nitride (Si3N4) reinforcements on the mechanical and tribological performance of 3D-printed PEEK composites fabricated via melt blending and fused filament fabrication (FFF). The composites exhibited uniform filler dispersion, good printability, and tensile properties comparable to neat PEEK, along with maintained thermal stability. Under impact loading, reinforced samples showed enhanced energy absorption and a transition from complete fracture to hinge-type incomplete fracture, indicating improved resistance to crack propagation. Tribological evaluation under simulated joint conditions revealed that hBN-reinforced PEEK reduced friction (∼20%) and wear (∼50%), whereas Si3N4-reinforced PEEK increased friction (∼40%) and caused noticeable damage to the cobalt–chromium (CoCr) counter surface. These findings highlight the potential of hBN as an effective reinforcement for improving the tribological performance of 3D-printed PEEK composites, while also revealing limitations associated with Si3N4.