Tribo-Mechanical Properties and Bioactivity of Additively Manufactured PAEK Materials for Load Bearing Medical Applications: A Systematic Review

Additive manufacturing (AM) has revolutionized medical applications, but the challenge of matching the mechanical performance of machined parts remains. Recent advancements in AM have pushed boundaries, yet challenges persist. 3D-printed parts exhibit lower tensile and flexural strength, coupled with inferior fracture toughness but higher microhardness, attributed to inherent anisotropy. This review explores the potential of poly-aryl-ether-ketone (PAEK) materials, especially polyetheretherketone (PEEK) and composites, to address these concerns. The paper highlights the necessity of thoroughly exploring the tribological behaviour of 3D-printed PAEKs in load-bearing orthopaedic applications with clinically representative configurations, allowing for further investigation into the long-term viability of these materials. The review evaluates surface modification approaches for enhancing biocompatibility, osseointegration, and performance of 3D-printed PEEK implants. Incorporating hydroxyapatite (HAp) into the PEEK matrix shows promise, but optimal HAp percentages vary. Optimizing pore size and coating composition within PEEK composites must balance mechanical properties and bioactivity. To guide future research, the review outlines critical directions. These include investigating surface modification techniques with PEEK composites, exploring bioactive additives, optimizing pore size and shape in PEEK scaffolds, and in-depth studies on long-term biocompatibility and osseointegration under dynamic conditions. 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.