Design, hybrid manufacturing, and characterization of porous fracture fixators

Abstract

Additive manufacturing (AM) enables the production of complex, highly porous geometries that would be impossible to create with subtractive methods. These geometries have generated much interest in their potential applications for decreasing the weight of traditional parts as well as their potential use in orthopedic implants, such as headless compression screws. Pore size and implant porosity play an important role in the osseointegrative performance of porous implants. Ensuring that the porosity of the physical part matches that of the CAD model is thus key to implant performance. However, more work is needed to design, fabricate, and evaluate the manufacturability of AM porous implants. The threefold objectives of this study are as follows. (1) Cylindrical screw blanks with three different porosity patterns are designed in CAD. (2) The blanks are fabricated using the laser-powder bed fusion (LPBF) process, followed by manual threading. (3) The resulting porosity of each LPBF blank is characterized using optical microscopy as well as micro-CT and compared to the CAD model. It was found that the as-printed porosity did not match well with the CAD model, with the measured mean pore size about 30% larger than the theoretical. Future work involves a redesign of the blank geometry to better integrate a porous core with threaded sections as well as mechanical testing to determine feasibility of use for fixation.