Page 375 - IJB-10-2

International Journal of Bioprinting AM evaluation of medical device companies

A first meeting was held individually with all of them. Six • Surface finish as per drawings provided, showing
companies did not meet the above-mentioned criteria; several ranges of rugosity from polished surfaces
therefore, they were disqualified for participating in the to “as built” surfaces in various areas of the
study. The other seven companies were evaluated. implant. The purpose was to discuss with each
manufacturer what different types of surface
2.2. Implant test design finishes they were able to perform and apply them
The pelvic implant was modeled with Unigraphics NX to the prototype as a sample. This was requested to
(Siemens, Texas, US), Geomagic Freeform Plus 2021 account for the variability of surfaces required on
(3D Systems, Rock Hill, US), and nTopology software metallic implants in different areas and different
(nTopology, New York, US) simulating a reconstruction functions. Surface roughness and controlled
to remove a pelvic tumor. A variety of design features topography can facilitate cell attachment and
were added with the purpose of testing the manufacturing improve osseointegration and bone healing.
13
capacity of the companies and not for clinical reasons. However, there are areas in implants that are
These included several screw holes, flanges, and four preferred to be smoothly polished to increase
surfaces of porous structures with different architectures. soft tissue-to-surface contact, reduce wear debris,
Several diamond and gyroid structures were chosen with a and improve dynamic contact for articulating
minimum beam thickness of 0.6 mm for lattices 1, 3, and 4 devices. 14
(L1, L3, and L4) and 0.5 mm for lattice 2 (L2).
• General tolerance ranging from 0.1 to 0.2 mm.
2.3. Design transfer for fabrication
• Prototype not for clinical use.
2.3.1. Manufacturing specifications proposed • Maximum quality to achieve: prototype to be
There are no standardized manufacturing requirements evaluated in terms of quality of manufacture.
for the optimal AM of pelvic custom implants. Therefore,
the following general specifications were prepared 2.3.2. Manufacturing specifications agreed
based on the literature and authors’ experience, and A second round of meetings was held with six out of
communicated to the companies prior to manufacturing. seven companies that requested a discussion about
These specifications were defined as general requirements the manufacturing specifications. We will refer to the
to be discussed with the companies so their manufacturing companies as “Company N” (CN) in the remaining
processes and standards could be identified and noted. paragraphs. Only company 7 (C7) gave no feedback and
• Material: Ti6Al4V, the gold-standard material to sent the manufactured part directly without consultations.
produce pelvic reconstructions and other load- For the other six companies, the manufacturing
bearing hard tissue due to its biocompatibility, specifications were adapted to each company’s capabilities,
mechanical properties, and corrosion resources, and standards, after discussion and agreement.
resistance. 10,11 The agreed requirements are given in Table 1.
• AM technology: either SLM or EBM, the most The feedback from companies about the
commonly used techniques to fabricate metallic manufacturing specifications was very diverse. C4
custom implants. 7 and C6 produced with EBM technology, while the rest
manufactured with SLM. Most companies were able
• Maximum density to achieve, 100% if possible, to offer hybrid manufacturing combining AM with
preventing voids as porosity is known to CNC machining except for C7. This company refused
negatively impact the mechanical properties of to manufacture the thread as they had to subcontract
SLM and EBM parts. 3 the operation. Only two companies, C5 and C6, agreed
• Avoid residual stresses from non-uniform heat. to perform the HIP treatment, and both of them had
The cooling rate during additive manufacturing to outsource the process. C5 always perform HIP
alters the microstructure of the part, affecting for orthopedic implants to improve their fatigue
mechanical performance. 7 performance. C6 did not consider it necessary, but they
performed it to follow our indications. The rest of the
• Hot isostatic pressing (HIP) to eliminate residual companies never perform HIP and had no experience
porosity and improve fatigue strength. 2,12
about the process. With regard to surface finish, we asked
• Manufacturing of a standard metric thread the companies for their preferred surface finish for the
(M12 x 1.75) in a specific hole (see Figure 1) as pelvic implant. Consequently, the prototypes received
per drawings provided. present different matte, satin, and mirror finishes.

Volume 10 Issue 2 (2024) 367 doi: 10.36922/ijb.0140