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Wang, et al.
interfaces. To obtain uniform microporous architectures, the PEEK/HA or PEEK/CS scaffolds can be close to the
a sulfonation treatment strategy is developed by fully values of natural bone by regulating HA/CS content and
immersing the 3DP PEEK scaffolds into concentrated porosity (Figure 11E-H). The PEEK/HA or PEEK/CS
sulfuric acid (95.0 – 98.0%) for 30 – 45 s (Figure 9A). scaffolds can significantly improve the MC3T3-E1 cell
The micropores (Figure 9B) with an average size of attachment and mineralization (Figure 11I-K), and the
0.19 ± 0.07 μm show little effect on the mechanical structural design and mechanical properties are the main
property of the whole PEEK implant (Figure 9C and D). regulatory factors for bone tissue engineering.
Furthermore, the micropores on the PEEK implant
significantly improve the cellular attachment, spreading, 6. Future perspectives
and proliferation, which can also facilitate the tight The 3DP PEEK implants have proven the feasibility of
adhesion of newly regenerated soft tissues to the PEEK reconstructing chest wall defects. A total of 114 clinical
implant (Figure 9E-G). cases in more than 40 hospitals in China have received
To obtain the uniform amidogen on the interface of
PEEK, O plasma and (3-aminopropyl) triethoxysilane chest wall reconstruction using the 3DP PEEK implants.
It is critical to forming a stable team, including engineers,
2
are successively coated on the 3DP PEEK scaffolds scientists, surgeons, and clinical research associates.
(Figure 10A-C). The amidogen PEEK (NPEEK)
significantly improves the cellular adhesion and migration The design methods, manufacturing process, and even
of the fibroblasts (L929 cells) (Figure 10D and E). implant surgery programs have improved with increased
Furthermore, soft-tissue ingrowth occurs more and clinical cases. In the whole process, engineers and
faster in the NPEEK interface after the NPEEK scaffold surgeons must work together for every special case. The
is embedded in the chest wall of rabbit (Figure 10F). surgical procedure must be recorded in detail, and the
In the animal experiment, a clathrate PEEK implant is patients should be followed up periodically after surgery.
fabricated to mimic the real sternal implant (Figure 10G). Except for the efficacy of 3DP PEEK implant, it is critical
The surgical procedures to reconstruct the chest wall to record the implant-related complication. The next
defects of rabbits are the same as the clinical surgery modification of manufacturing process is originated from
for humans. The PEEK implant with amidogen interface the main implant-related complication. The concept of
can remarkably reduce the healing time and incision biofabrication originated from clinical practice and was
complications (Figure 10H and I). The micropores and finally applied to clinical practice.
amidogen on the interface of PEEK implants proved the The 3DP PEEK implants need to be approved by
effectiveness of soft-tissue ingrowth, as reported in the the Food and Drug Administration or National Medical
previous studies. Products Administration. Personalized implants are an
It is worth mentioning that the displacement important development trend in future medicine, but they
and rupture of the 3DP PEEK implant after surgery also bring new challenges to the regulatory authorities.
infrequently happened in the follow-up period because The qualification rate of conventional implants can be
sternum and ribs are the non-load-bearing bone and tested by sampling, but this method is not suitable for
the implants do not have to carry too much load. As an personalized implants. It is difficult to test the physical
orthopedic implant, enhancing the osseointegration can and chemical properties of personalized implants because
increase the stability of the implants in vivo. Thus, we all implants are different, such as shape, and mechanical
further manufacture 3DP PEEK composite scaffolds properties. The regulators cannot test the properties
with hydroxyapatite (HA) or calcium silicate (CS) of every personalized implant in clinical practice.
contents in gradient through FDM 3D printing techniques This is why there are no commercialized personalized
(Figure 11A) [47-49] . The PEEK (50 μm) and additives (HA implants in clinical practice. Although some implants are
or CS powder) (Figure 11B and C) are first mixed with fabricated by 3DP technology, they are still classified by
a mass ratio (PEEK: HA = 8:2; PEEK: CS = 6:4). Then, product size or materials: Standardized implants and not
the filaments with a diameter of 1.75 mm are extruded personalized implants. 3DP technology can save on raw
using the PEEK and additives mixture in a twin-screw materials and is more suitable for implants with complex
extruder. The filaments are further used to fabricate internal structures. Thus, many acetabular cups with
tetragonal scaffold samples (length, width, and thickness specific sizes are made using 3DP technology globally, but
of 10 mm) through FDM process. The PEEK and these acetabular cups cannot be regarded as personalized
additives (HA or CS particles) are uniformly distributed implants. Possibly, testing of implants could be replaced
in the filaments and the scaffold samples (Figure 11D). by supervising production lines or equipment of 3DP
The modulus of the PEEK/HA scaffold increase relative implants in the future. Adjusting regulatory policies and
to the rise of HA content, while the strength and failure improving production technology can bring new vitality
strain concomitantly decreased. The elastic modulus of to the industrialization of 3DP personalized implants.

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