<title>Reverse engineering of radial head replacements from CT imagery</title>

Abstract

Commercially available orthopaedic implants used to replace a fractured or damaged radial head in the elbow are limited because the simplified axisymmetric design only approximates the normal bone anatomy. An implant that more closely approximates the normal anatomy of the radial head is likely to be superior to the ones of standard shapes and sizes. This paper provides a description of how reverse engineering technology is being used to replicate the geometry of the radial head from computer tomography imagery. Reverse engineering is the process of generating accurate 3D CAD models of free-form surfaces from measured coordinate data. In this application, shape information of the bone is extracted from CT images, translated into global coordinates, and transferred to a CAD software package in order to generate a solid model of the radial head region. The solid model is formed by creating contours from edge points, lofting these contours, and then joining the lofted contours. The tool-path for machining the implant device on a computer numerically controlled milling machine is generated from the solid model. The results of an experiment are presented in order to demonstrate the effectiveness of this approach to reverse engineering and manufacturing radial head replacements.