Manufacturing evaluation of seven medical device companies during the production of a 3D-printed titanium pelvic implant

Abstract

Powder bed fusion (PBF) technology has become a popular manufacturing method to fabricate custom metallic implants. This trend has generated some regulatory concerns because traditional developing guidelines are not suitable for three-dimensional (3D)-printed implants. This is due to the layered microstructure of additive manufactured parts that produces mechanical properties different than those of traditionally manufactured parts. The inappropriate choice of the process parameters and postprocessing methods can lead to fabrication errors that could negatively affect mechanical properties and dimensional accuracy. The objective of the study was to perform a preliminary evaluation of the quality of manufacturing provided by the medical device industry and identify the best 3D printing practices. We designed a pelvic bone reconstructing implant and asked seven companies to manufacture it in Ti6Al4V with PBF technology. We inspected some important aspects of the manufacturing quality of the prototypes received by evaluating geometrical precision and microstructural integrity in the surface and in the matrix, including a qualitative assessment of voids and grain morphology. Results demonstrated a great difference among the implant prototypes. Two companies proved to be superior and provided defect-free implants. The other five produced evidence of some defects including: geometrical deviations (maximum values of up to 5 mm); heterogeneous acicular grain morphologies; broken sections of lattice structures; and internal and superficial voids and cracks that could potentially compromise functional and clinical performance. To our knowledge, this is the first study analyzing the production of several custom implant additive manufacturers based on a geometrical and microstructural evaluation of the same pelvic implant fabrication. The imperfections found in some prototypes produced by companies certified to commercialize personalized implants highlight the urgent need for technical standards that regulate the safe development of 3D-printed implants. Further analyses are required to determine the actual clinical and mechanical consequences of such imperfections. The results also show that when additive manufacturing is adequately managed, it can be a valid manufacturing method to fabricate defect-free implants.