Additive manufacturing of orthopedic implants

Additive Manufacturing (AM) is the process of selectively joining materials to fabricate objects in a layer-by-layer approach using digital part information, i.e. 3D CAD models. This definition highlights the fundamental difference between AM process and traditional manufacturing methods such as subtractive processes (e.g. machining), forming processes (e.g. forging) and bulk solidification processes (e.g. casting). AM is often also called 3D printing, additive processes, freeform fabrication and layered manufacturing. When compared to traditional processes, AM offers unique advantages to economically produce low volume batches (one to a few) of highly complex products. Since AM does not require design and/or material dependent tooling (e.g. jigs and fixtures), AM is an ideal candidate for the next generation design and manufacturing of orthopedic implants. Although “customization” of product specifications implants has been around long before the introduction of AM technology to the medical field, the lack of tooling requirement for each design in AM makes it economically viable for patient-specific orthopedic implant production. Finally, design freedom that can be easily achieved through AM technology enables introduction of porous structures for bone ingrowth and biological implant fixation. The motivation for this chapter is to understand the current state of orthopaedic applications of AM which have been shown to economically produce highly customized and highly complex design features in low volumes.