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Wang, et al.
thus resulting in 3D anisotropy of additive manufactured of the implants, including the horizontal type (Figure 8A),
PEEK prosthesis. The highest mechanical properties of E type (Figure 8B), and vertical type (Figure 8C). The
the printing direction may approach injection molding, category of implants can be better used in clinical practice.
while those of the weakest direction may be less than half As for the implants for ribs reconstruction, the strength of
of that . Therefore, for the large size prosthesis model, the joint area is key point in the manufacturing process.
[42]
it is critical to adopt appropriate placement through The 3DP PEEK implant is bound with the residual ribs
stress analysis and performance demand analysis to using the titanium wire and fixed with the sternum using
ensure that the anisotropy conforms to the biomechanical two titanium screws (Figure 8A). Thus, the 3DP PEEK
environment of the implants. implants are fixed through a rigid connection. FDM
process in the joint area was used here to fabricate the
3.4. Manufacturing process of personalized joint area of 3DP PEEK implants with enough hardness
sternal rib implants and strength. In addition, the connector structure is
another factor affecting the stability of implants. The
Sternal rib implants can accurately repair the sternal implants cannot be fixed in a symmetric position due
defect of patients to ensure sufficient mechanical, to the irregularity of the costal arch, making for the
biological safety and long-term reliability. To reduce instability of the implant after surgery. Thus, the implant
the loss of respiratory function after implant surgery, is designed as a massive structure (E type), possessing
the designed thoracic rib model can be divided into four multiple junctions with the residual ribs and upper ribs
functional areas for different manufacturing processes adjacent to the defect. The E-type implant was fixed
(Figure 7). with the residual ribs and the upper rib adjacent to the
Sternum area (high stress and high deformation defect (Figure 8B). The multiple junctions can confirm
area): Sternum is one of the most important bones to bear the stability of the implant after surgery. The vertical type
the load and protect viscera, which requires high stiffness implants are used to repair the chest wall defects adjacent
and enough strength. In addition, given the cyclic to the spine because it is difficult to fix the implants with
deformation caused by respiration, requires sternum area the spine in accordance with the anatomic structure. In
in the implants also needs a certain toughness. Therefore, this case, the connector of implants is designed as a flat
for the 3D printing process, one of the feasible schemes and semi-arc shape to adhere to the rib tightly, and the
is that the outer layer of the sternal region has a very high implant is bound with the upper and lower ribs adjacent
crystallinity (≥35%) with a thickness of about 3 mm, to the defect using titanium wire (Figure 8C). At last,
while the inner region has a very low crystallinity (≤25%). a pericardial patch was suspended under the 3DP PEEK
Rib area (high deformation area): Costal cartilage implants to close the thorax. It is necessary to use the
that exists in the human body can generate the right biological patch to isolate the PEEK implants from the
amount of deformation in human breathing. Therefore, to lung because the hydrophobicity of PEEK materials can
get the lowest modulus possible, the 3D printing process prevent the adhesion of soft tissues. In addition, the patch
in the rib area should be designed to get a very low was fixed with the 3DP PEEK implants using the sutures,
crystallinity (≤25%) for the implants. and no motion happened between the PEEK implants
Joint area (wear resistance, connection area): and patch. In our hospital, 49 patients received ribs
This area needs a good hardness and abrasion resistance reconstruction using 3DP PEEK implants, including 34
to guarantee long-term connection reliability, the of horizontal type, six of vertical type, and nine of E type.
crystallinity in this area can be designed to be 30 ± 2% The main chest wall diseases were primary and metastatic
by the 3D printing process with moderate temperature tumor. The average chest wall defect size was 220.0 ±
conditions. 120.5 cm (64– 700 cm ).
2
2
Transition region: To avoid stress concentration,
the transition region should be manufactured to get an 4.2. Large size individualized 3DP PEEK
appropriate crystallinity variation between different implants for sternum defects
contiguous crystallinity areas. We classified sternal defects into three categories

4. Application of 3DP PEEK implants for according to the defect site, including the whole sternum,
personalized chest wall reconstruction manubrium sterni, and mesosternum defect. Furthermore,
we designed and fabricated the individualized 3DP
4.1. Large size individualized PEEK implants for PEEK implants according to the sternum defect types
ribs defects (Figure 8D-F). Herein, reliable mechanical links are key
to implant stability. For the whole sternum implant, we
In general, the 3DP PEEK implants for ribs reconstruction usually use wires to bind the implant with residual ribs
can be divided into three categories according to the shape embracingly (Figure 8D). The side through-hole must be

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