Fused Deposition Modeling PEEK Implants for Personalized Surgical Application: From Clinical Need to Biofabrication

Abstract

Three-dimensional printing (3DP) technology is suitable for manufacturing personalized orthopedic implants for reconstruction surgery. Compared with traditional titanium, polyether-ether-ketone (PEEK) is the ideal material for 3DP orthopedic implants due to its various advantages, including thermoplasticity, thermal stability, high chemical stability, and radiolucency suitable elastic modulus. However, it is challenging to develop a well-designed method and manufacturing technique to meet the clinical needs because it requires elaborate details and interplays with clinical work. Furthermore, establishing surgical standards for new implants requires many clinical cases and an accumulation of surgical experience. Thus, there are few case reports on using 3DP PEEK implants in clinical practice. Herein, we formed a team with a lot of engineers, scientists, and doctors and conducted a series of studies on the 3DP PEEK implants for chest wall reconstruction. First, the thoracic surgeons sort out the specific types of chest wall defects. Then, the engineers designed the shape of the implant and performed finite element analysis for every implant. To meet the clinical needs and mechanical requirements of implants, we developed a new fused deposition modeling technology to make personalized PEEK implants. Overall, the thoracic surgeons have used 114 personalized 3DP PEEK implants to reconstruct the chest wall defect and further established the surgical standards of the implants as part of the Chinese clinical guidelines. The surface modification technique and composite process are developed to overcome the new clinical problems of implant-related complications after surgery. Finally, the major challenges and possible solutions to translating 3DP PEEK implants into a mature and prevalent clinical product are discussed in the paper.

Keywords: Chest wall reconstruction; Fused deposition modeling; Polyether-ether-ketone; Three-dimensional printing.

Figure 1

The design and von Mises stress of the implant for chest wall reconstruction. (A) In-suit rib reconstruction; (B) costal arch reconstruction; (C) vertical reconstruction; (D) whole sternum reconstruction; (E) upper segment sternum reconstruction; and (F) upper segment sternum reconstruction.

Figure 2

Design and evaluation of the in-suit rib prosthesis. (A) Resection plan of the tumor and ribs, (B) Scheme of the in-suit reconstruction, (C) generation of the body part of the rib prosthesis through centroid trajectory, (D) load and boundary of the FEA model of the rib and prosthesis, (E) the von Mises stress of the rib prosthesis, (F) the von Mises stress of the corresponding natural rib, (G) mechanical testing of the 3D-printed rib prosthesis, (H) the deformation pattern during of the bending test, and (I) the deformation of the in-suit rib prosthesis at different sagittal displacement (left) and a comparison of the relative displacement between experimental and FEA results.

Figure 3

Bionic costal cartilage made of PEEK. (A) Design of wavy elastic structure; (B) 3DP PEEK wavy structure; (C) FEA results of different wavy structures; (D) bending test of the wavy structure; (E) tension test of the wavy structure; and (F) the comparison of the uniaxial stress-strain relationship between the adjustment range of the wavy structures and natural costal cartilages in tensile tests[38].

Figure 4

3D printing technology for PEEK implants. (A) Fused deposition modeling (FDM) process; (B) influence factors of crystallization; (C) FDM equipment; (D) crystallization regulating; (E) mechanical properties regulating; and (F) different local crystallinity structure.

Figure 5

Crystallization and mechanical properties regulating. (A) Schematic diagram of the module with a heat collector module; (B) the new nozzle model; (C) the temperature distribution around the nozzle; (D) temperature profiles around the printer head; (E) tensile; and (F) bending results of printed PEEK specimens under different conditions[68].

Figure 6

Process parameters of FDM and the mechanical properties of PEEK materials. (A) Tensile property of PEEK; (B) SEM images of fracture cross-sections of PEEK; (C) fractured tensile specimens; (D) comparison of tensile properties for different printing parameters; and (E) impact strength and absorbed energy[70,71].

Figure 7

The manufacturing process of personalized sternal rib implants. (A) Performance requirement analysis of sternal prosthesis. (B) Printing path planning and a close-up of the support structures. (C) 3D-printed PEEK sternal rib implants.

Figure 8

The 3DP PEEK implants of horizontal type (A), E type and (B), vertical type and (C), corresponding chest wall reconstruction surgery images. The 3DP PEEK implants for whole sternum (D), manubrium sterni, and (E) mesosternum (F) defect, and corresponding chest wall reconstruction surgery images. The incision ulcer and 3DP PEEK implant exposure. (G) After the surgery (the black circle point out the PEEK implant). The displacement of 3DP PEEK implant in the rib (H and I) residues (the white circle points out the displacement part).

Figure 9

Schematic diagram of the preparation process to create the microporous architectures in the FDM PEEK scaffolds (A); SEM images of SHPEEK scaffolds with a sulfonation processing time of 30 s (B); the comparison of compressive strength (C) and compressive modulus (D) in FDM PEEK, HPEEK, and SHPEEK scaffolds; the comparison of cellular proliferation in FDM PEEK, HPEEK, and SHPEEK scaffolds using CCK-8 method (E); the comparison of deposited calcified nodules in FDM PEEK, HPEEK, and SHPEEK scaffolds (F); HE staining and SEM images of soft-tissue ingrowth into the FDM HPEEK and SHPEEK scaffolds in vivo for 2 weeks (G) (*P < 0.05 and **P < 0.01)[45].

Figure 10

Schematic diagram of FDM PEEK implant modification and animal experiment results (A); SEM images of the interface on amidogen PEEK (B); three-dimensional images of the interface on amidogen PEEK (C); the comparison of cellular proliferation in FDM PEEK, NPEEK scaffolds, and blank materials using CCK-8 method (D); the comparison of cell migration on NPEEK and PEEK interfaces using wound healing assay (E); HE staining and SEM images of soft-tissue ingrowth into the FDM PEEK and NPEEK scaffolds in vivo for 2 weeks (F); the clathrate PEEK or NPEEK implants and the rabbit after chest wall reconstruction surgery (G); the comparison of drainage fluid (H) and extubation time (I) after chest wall reconstruction surgery in FDM PEEK and NPEEK groups (*P < 0.05, **P < 0.01 and ***P < 0.001)[46].

Figure 11

Schematic diagram of the preparation processes of PEEK/additives composites and FDM technology (A); the SEM images of PEEK granular material (B) and HA powders material (C) (white bar, 100 mm; yellow bar, 50 mm); geometry images of PEEK/HA and PEEK/CS scaffolds under micro-CT (D); SEM images of PEEK/HA and PEEK/CS scaffolds (E); the comparison of compressive modulus (F) and compressive strength (G) in PEEK/HA scaffolds with different pore sizes; the comparison of compressive modulus of the PEEK/CS scaffolds with different CS content and raster angles (H); the comparison of cellular proliferation in PEEK/HA scaffolds with different HA content (white bar, 400 mm); the comparison of alizarin red staining (J) and Alizarin red staining (K) of MC3T3-E1cells on the PEEK/HA scaffolds with different HA content[47-49].