Design and fabrication of CoCrMo alloy based novel structures for load bearing implants using laser engineered net shaping

Designing load bearing implants with the desired mechanical and biological performance and to fabricate net shape, functional implants with complex anatomical shapes is still a challenge. In addition, patient specific load bearing implants with the possibilities of guided tissue regeneration are gaining significant interest in orthopedics. Novel design approaches and fabrication technologies that can achieve balanced mechanical and functional performance in mono-block implants are necessary to accomplish these objectives. In this article we give an overview of our novel design concepts for load bearing metal implants and demonstrate the manufacturing of unitized implant structures with and/or without porosity using laser engineered net shaping (LENS™) — a solid freeform fabrication technique. We have fabricated porous metal implants with designed porosities up to 70 vol.% in various biomedical metals/alloys, such as Ti, Ti6Al4V, NiTi and CoCrMo, and tailored their effective modulus to suit the modulus of human cortical bone, thus eliminating stress-shielding. Unitized structures with functionally graded CoCrMo alloy coating on porous Ti6Al4V alloy have been fabricated using LENS™ to minimize wear induced osteolysis. Finally, this technology can also be used to fabricate porous, net shape implants with functional gradation in structure and/or composition to mimic natural bone. Since the LENS™ fabrication does not change the chemistry of the biocompatible alloys the inherent in vitro and in vivo biocompatibility will remain the same and therefore, we have not provided any biocompatibility results in this article. This article provide an insight into the important aspects of LENS™ fabrication and properties of CoCrMo alloy structures, which can potentially eliminate long standing challenges in load bearing implants such as total hip prosthesis to increase their in vivo life time.