Characterization of the Chemical and Mechanical Effects on Ti6Al-4V ELI Grade 23 Interbody Devices Using Recycled Powder

Introduction: Additive manufacturing for medical implant-grade titanium has an increasing use in orthopaedic and spinal implants because it allows complex designs combined with porous or lattice structures that promote improved osteointegration compared to surface of machined implants. The current requirement is to use virgin powder for all medical device manufacturing since degradation of powders resulting from repeated reuses has been found to be problematic; however, there is a lack of understanding about the changes in chemical and mechanical properties as powder is recycled.

Aim: Characterize the overall strength per ASTM F2077 and ASTM F3001 of finished Ti6Al-4V ELI Grade 23 interbody devices. Devices will first be 3D printed from virgin material with elemental analysis and consolidated material chemistry properties conforming to Table 1 of ASTM F3001. The same powder, without any modifications, will then proceed to be reused multiple times with the chemical composition migrating out of tolerance of Table 1 of ASTM F3001. The mechanical and chemical characteristics will be assessed for each repeated reuse.
Materials and Methods: Specimens will be manufactured of Ti6Al-4V ELI Grade 23 using a Direct Metal Laser Melting (DMLM) additive manufacturing process using virgin powder. The specimens will be manufactured to representative size and shape of a common Posterior Lumbar Interbody Fusion device (PLIF). The powder from which the specimens will be manufactured will be tested for the chemical composition per ASTM F3001 while the manufactured specimens will be mechanically tested per ASTM F2077 Dynamic Compression Shear. The same powder used from the first virgin production will then be reused and the process of chemical testing per ASTM F3001 and mechanical testing per ASTM F2077 will be repeated for up to five reuses.

Hypothesis: Mechanical and chemical properties of additively manufactured Grade 23 Ti-6Al-4V ELI implants do not change over five re-uses of powder.