Preclinical Testing of a Novel, Additive-Manufactured, Three-Dimensional Porous Titanium Structure

• Published in: Structural Integrity of Additive Manufactured Materials and Parts pp. 322 - 339
• Main Authors: Woodard, Erik, Post, Zach, Morrison, Mark
• Format: Book Chapter
• Language: English
• Published: 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959 ASTM International 01.09.2020
• Subjects: Laser Powder Bed Fusion; Manufacturing Engineering; Materials & Manufacturing Processes; Orthopedic Implants; Porous Structure
• ISBN: 9780803177086; 0803177089
• DOI: 10.1520/STP163120190139

When considering orthopedic implants for bone growth, several factors such as porosity, pore size, stiffness, friction, and strength can affect bone growth and contribute to the long-term success of the implant. Additive manufacturing is one tool to help achieve the ideal factors for implant structures and materials. Smith+Nephew has developed an additive manufactured (AM), Ti-6Al-4V advanced porous structure designed to be similar to cancellous bone with up to 80% porosity. This structure is currently used as part of both acetabular shells and augments. This paper describes the preclinical testing of this advanced porous structure that comprised coupon-level and device-level testing. The critical parameters that can influence bone ingrowth, such as pore size (mean void intercept length, or MVIL) and porosity, were measured. The ability of the three-dimensional porous structure to withstand compressive, tensile, and shear forces was evaluated in static (monotonic) testing. Finally, bone ingrowth was assessed in a load-bearing ovine model. Clinically relevant device-level fatigue testing was conducted in foam blocks with a cavity and adjacent rim defect to simulate the acetabulum. The strength of the locking screw hole features was assessed using static and fatigue cantilever bending and pull-through strength. Acetabular constructs were also fatigue tested in an unsupported model with an adjacent augment and corresponding defect. Constructs completed all clinically relevant fatigue testing with no fractures.