Creating Implants from Allograft Bone using Subtractive Rapid Prototyping

This research involves the development of rapid manufacturing for bone implants using human allograft bone in a Subtractive Rapid Prototyping process. Using CT-derived CAD models of missing bone due to high energy trauma or tumor resection, surgical reconstruction could be improved with custom rapid implants made from natural bone. The bone “stock” material is of arbitrary shape and material distribution in the form of frozen donated cadaveric bones. Each is unique in shape and has highly anisotropic material properties; likewise for each final bone implant geometry and its material distribution. This work utilizes a PLY input file, instead of the more common STL, using color texture information that can be utilized for advanced process planning depending on whether the surface is fracture, periosteal or articular in origin. Moreover, we present a new PLY assembly model, called the Matryoshka model, where successively nested PLY files are used to designate changing material distributions in the donated bone; a method that could also aid in the use of multi-material additive RP systems. Using color Matryoshka models and their subsequent color slice files; this work presents novel solution methods for the selection of implant harvesting sites and automated process planning for the physical rapid prototyping process. Early implementations using bone surrogate materials will be presented.