Page 281 - Advances in Biomechanics and Tissue Regeneration

14.4 3D PRINTING OF PERSONALIZED SILICONE IMPLANT 279

The most recent implant design that can be used for restenosis patients (but aimed more generally at patients with
swallowing disorders) is the NewBreez implant developed by the company PROTiP Medical, which fits between
the vocal cords and recreates a true laryngeal sphincter [71, 72].
b. Tracheobronchial level

Even incomplete, the endoscopic management always has an immediate effectiveness, often with immediately
evident outcomes. For complex stenosis, the placement of an endotracheal prosthesis after dilatation at the first endos-
copy is justified by the risk of partial inefficiency of the simple dilation and the very high risk of rapid recurrence,
Fig. 14.6A–D [73]. The advantage of the silicone-based materials for the development of these soft implants is its
inherent flexibility characteristics, bio-inertness, being not traumatic for the tracheal mucosa, and low immune
response, Fig. 14.6E.

14.4.2.3 Complications Related to Standard Prostheses
As all these implants will be inserted in the laryngotracheobronchial tract, a geometry close to patient anatomy is
required. For most of the cases, all the available standard sizes developed by the manufacturer is sufficient. Never-
theless, depending on patient medical background (cancer, multiple surgeries, other diseases), larynx, trachea, or bron-
chus tracts can be deformed and then the standard stents or intralaryngeal implant can no longer be used and then a
specific custom implant needs to be designed.
If the implant does not fit correctly patient anatomy, the implant can migrate in the airway tract or just be inefficient
due to the lack of anatomical conformity and that can lead to severe medical complications such as the following:
- Excessive inflammation
- Pulmonary aspiration
- Infection
- Airway obstruction with asphyxia
- Mucosal necrosis (excessive pressure exerted by the implant on the tracheal wall)
Most of these medical complications will require the removal and the replacement of the prosthesis leading to emer-
gency hospitalization. These complications impact directly patient quality of life and increase the cost of medical care.
To overcome this problem, personalized 3-D printed implants can be an interesting solution because it provides an
implant with a geometry that fits patient anatomy, which can decrease dramatically the risk of complications.
In an European study of 263 patients treated with prosthesis for tracheal stenosis, the percentage of migration and
obstruction was respectively 18.6 and 5.7% [74].

14.4.3 Benefits of 3D Printing

As mentioned earlier, the benefits of 3-D printing technique to develop medical implants will be at different levels:
- For customization and personalization
- Cost efficiency
- Time efficiency
First, 3-D printing technology allows the design of custom-made medical implants that can really fit to patient anat-
omy, and this will increase the efficiency of the implant, prevent implant related complications due to the anatomical
and mechanical misfits, and overall increase the patient quality of life after implantation. For example, for patients
having anatomical defects that prevent the use of standard implants prepared using injection molding technique such
as deviation of the tracheal or laryngeal tracts, bronchus malformation, or cardiac malformation, this technique is able
to produce implant with complex geometries that will take into the consideration the specific features of the patient
anatomy for offering conformity.
Another important aspect is the cost efficiency. This technique will allow producing cheaper medical implants but
currently only when it concerns small series. Other conventional techniques for the moment are less expensive for
large-scale production. Techniques such as injection molding are more economic for the production of big series of
implants because once a mold is produced, it can be used for the production of thousands of similar implants. Nev-
ertheless, this manufacturing technique does not allow to develop personalized implant that fits patient anatomy, and
a size range must be fixed for a given implant as the limiting step of developing molds will only allow a specific

II. MECHANOBIOLOGY AND TISSUE REGENERATION