## 3 Polyaryletterketone
### Polyetheretherketone (PEEK)  
PEEK has gained attention for its potential use in orthopedic implants due to its exceptional biocompatibility, chemical resistance, sterilizability, and mechanical properties, such as stiffness and strength, which closely mimic those of human bone [28; 30]. Additionally, PEEK does not present the same issues, with local inflammation and stress shielding commonly associated with metallic implants, making it a promising biomaterial [28]. PEEK has already been applied in various fields, including spinal fusion cages, dental implants, and maxillofacial reconstruction [27]. PEEK demonstrates exceptional mechanical strength, largely attributed to its polymer structure, which provides rigidity and resilience under stress [32]. This makes PEEK particularly well suited for applications in spinal implants, where it must endure significant mechanical loads over time without deforming or breaking down. Its durability allows for PEEK implants to effectively support the spine, even in cases of high-level stress or strain, such as those experienced during movement or physical activity [32; 33]. In addition to its mechanical robustness, PEEK's radiolucent nature sets it apart from the traditional metallic implants. This property allows for clearer radiographic imaging, which is crucial for evaluating bone fusion after spinal surgery. Unlike metallic implants that can obscure the imaging results, PEEK enables surgeons to closely monitor the healing process and assess the effectiveness of spinal fusion procedures without interference. It is particularly valuable in postoperative care, as it allows for more accurate diagnostics and timely interventions if needed [26; 29; 32; 33]. The combination of high mechanical strength and radiolucency makes PEEK an ideal material for spinal implants, where both the load-bearing capacity and the ability to monitor bone healing are critical to patient outcomes [34; 35]. Ongoing advancements in PEEK-based technologies, such as surface modifications and bioactive coatings, continue to enhance their performance, making them an increasingly popular choice in spinal and orthopedic surgeries [4; 36; 37]. PEEK is considered bioinert due to its poor integration with surrounding tissues [27; 28]. However, various methods have been proposed to make PEEK bioactive [28; 38; 39]. Several methods have been proposed to improve the bioactivity of PEEK, such as chemical or plasma treatment to modify the surface, coating with plasma spraying or sputtering, and the direct fabrication of composite materials with bioactive agents through injection molding or 3D printing [27; 39; 40]. One such method involves the manufacturing of composite materials and the addition of bioactive agents such as hydroxyapatite (HA) into PEEK. It has been demonstrated that this approach could provide a suitable solution [27; 41; 42]. HA belongs to the apatite family, a group of crystalline compounds with a hexagonal lattice structure [43]. The primary applications of synthetic HA Ca\({}_{10}\)(PO\({}_{4}\))\({}_{6}\)(OH)\({}_{2}\) are bone graft material to fill bone defects, bioactive implant coatings, dental surgery materials, and craniofacial and maxillofacial reconstruction materials particularly [44]. It is considered that synthetic HA has similarities to bone apatite in terms of chemical composition, structure, and size, and these features can provide exceptional osteeconductive and osteeintegrative characteristics [41; 45; 46; 47]. Compared to those of other bioactive ceramic glasses (such as Bioglas(r) or A-W glass-ceramics, the primary advantage of employing HA as a biomaterial or biocearamic is its chemical resemblance to the inorganic constituents of bone and teeth [41]. It is primarily utilized in the repair of hard tissues such as bones and can be employed