![]() This is an alternative to bolstering osteoconductivity through coatings and composites, which can negatively impact mechanical performance, imaging compatibility, material cost, and ease of manufacturing (Torstrick et al., 2017, 2018 Bakar et al., 2003 Mahjoubi et al., 2017 Harting et al., 2017). The interconnected pores of these networks create scaffolding that mimics bone morphology, provides anchorage for cell attachment, and allows for vascularization, thus exhibiting inherent osteoconductivity (Karageorgiou and Kaplan, 2005). And while clinical concerns exist regarding the bioinert nature of PEEK and, consequently, its limited ability to interact with bone to establish fixation, the introduction of porosity has shown promising results for promoting the osteogenic potential of PEEK (Kurtz and Devine, 2007 Torstrick et al., 2017 Landy et al., 2013 Wang et al., 2018). However, significant drawbacks of these methods, including harmful debris generation, damage to host bone through stress shielding, attenuated bone fixation, and high costs have led to a push for alternative orthopaedic bone ingrowth surfaces (Du et al., 2018 Cowie et al., 2016 Newman et al., 2018). The success of such implants relies on long-term fixation at the bone-implant interface, currently achieved via cementation or porous metal surfaces. While machined PEEK interbody fusion devices have been used for spinal fusion treatments with positive results since the early 2000's (Kurtz, 2012), interest in PEEK for total joint arthroplasty (TJA) has recently been growing (Du et al., 2018 de Ruiter et al., 2017 Cowie et al., 2016). PEEK has a modulus of elasticity similar to bone, high yield strength and fatigue resistance, and natural radiolucency, making it an attractive biomaterial for implantable medical devices (Panayotov et al., 2016 Honigmann et al., 2018). While FFF has thus far been suitable only for low temperature plastics, recent innovations in FFF have allowed for the printing of high temperature, implantable polymers such as polyetheretherketone (PEEK), opening the door for more advanced osteoconductive surfaces. Even the dominant method for creating AM osteoconductive scaffolds, laser-based metal sintering, comes with significant cost and safety considerations, unlike the extrusion-based fused filament fabrication (FFF) method already being used in-hospital to create custom non-implantable instruments. However, there are reported drawbacks to many of these materials, including dimensional inaccuracy and inadequate mechanical properties (Bobbert et al., 2017 Yang et al., 2019 Lin et al., 2019). AM methods already have a history of use for creating synthetic osteoconductive materials that, in addition to avoiding morbidities related to auto- or allografts, can be bio-functionalized and highly customized (Bobbert et al., 2017 Yang et al., 2019 Lin et al., 2019). This is especially true for osteoconductive surfaces used for orthopaedic implant surfaces or bone defect repair, which benefit from complex trabecular-like morphology not achievable by traditional manufacturing. ![]() In recent years, clinical interest in additive manufacturing (AM), or 3D printing, of biomaterials has been rapidly growing. SEM imaging revealed cells attaching to and bridging micro-topological features of the porous constructs, and cell activity was significantly greater for the porous PEEK compared to solid at multiple time points. Average compressive properties ranged from 210 to 268 MPa for elastic modulus and 6.6–17.1 MPa for yield strength, with strength being greatest for TPMS constructs. μCT imaging showed the porous networks to be open and interconnected, with porous sizes similar (p > 0.05) to the as-designed size of 600 μm. The samples were then imaged via scanning electron microscopy (SEM) to observe cell morphology. The porous PEEK, along with 3D printed solid PEEK, was then seeded with MC3T3-E1 preosteoblast cells for evaluation of cell proliferation and alkaline phosphatase (ALP) activity. The material characteristics, including porosity, yield strength, and roughness, were evaluated using μCT, static compression testing, and optical profilometry. ![]() The designs of the porous structures were based on a simple rectilinear pattern as well as triply periodic minimal surfaces (TPMS), specifically gyroid and diamond types. In this study, we created porous PEEK via clinically-available fused filament fabrication (FFF, 3D printing) and assessed the pore structure morphology, mechanical properties, and biologic response. Though concerns exist regarding PEEK for orthopaedic implants due to its bioinertness, the creation of porous networks has shown promising results for interaction with surrounding tissue. Due to its unique and advantageous material properties, polyetheretherketone (PEEK) is an attractive biomaterial for implantable devices. ![]()
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