A route for digital design and manufacturing of customised maxillofacial implants

Abstract

Rapid Prototyping (RP) techniques as a part of Engineering Assisted Surgery TM enables manufacturing of customised implants and prostheses prior to surgical procedures. Using CT or MRI scans, a biomodel of the bone structure of an individual patient can be generated quickly on which a prosthesis can be designed. Though the prosthesis' shape will be based on the patient's individual bone structure, surgical procedures are not necessary until the prosthesis is implanted, which significantly reduces surgery time. Peckitt reported on such a prosthesis in [1]. However, significant improvements in accuracy and design were achieved by digitising the design route of an existing maxillofacial implant developed by Peckitt, and in working with a virtual biomodel the fabrication of a physical biomodel was avoided. As a result, several interchanges between physical and virtual biomodels, which are prone to introduce geometrical errors, were also avoided. The prosthesis was designed using CAE software, based on the virtual biomodel generated from the CT scans, which allows one to preserve the facial aesthetics very well even when large resections are necessary. Having digital models, a finite element analysis of the prosthesis was easily introduced into the design route to optimise the shape for mechanical requirements and find potential possibilities for weight reductions by a leaner profile. The analysis gave an estimation for the minimum wall thickness of the prosthesis, depending on the material used. Eventually, the prosthesis was rapid manufactured from titanium and a quality control system was defined to check the implant's dimensional accuracy. What resulted was a streamlined and completely computer based process for design and manufacture, allowing high accuracy and flexibility in the geometrical design of the implant.