Computer-aided development of mega endo-prostheses

Abstract

Prosthesis refers to an artificial implant that can replace or substitute for a natural joint, and maintain the desired functionality, including cosmetic appearance. They are needed when joints are lost by injury (traumatic), missing from birth (congenital), or damaged by disease (such as cancer), and thereby save the remaining limbs. While a prosthesis can also be external (as in an artificial limb for amputees), the focus of this chapter is on internally placed artificial joints (or endo-prosthesis), especially those that fully replace a joint along with part of the bone (mega endo-prostheses), and provide the required functionality (see Fig. 10.1). They can be classified in different ways, depending on the articulation or site of joint, freedom of movement, material combination, extent of customization, indication for the replacement, and the fixation method. The development of such prostheses is highly challenging, requiring inter-disciplinary inputs from orthopedic surgeons, mechanical engineers, and material scientists, supported by information technology. The development of any new prosthesis begins with the study of the patient requirements. Bio-mechanical studies are needed to determine the loads, movements, and other functional requirements of the joint. The configuration and design have to be evolved depending on the functional requirements, but compatible with the selected implant materials and manufacturing processes. Bio-compatible materials with the desired properties need to be selected for various components of a prosthesis. Manufacturing processes must be planned to achieve the desired functionality, reliability and cost. Surgical instrumentation (called armamentarium) to implant the prosthesis must also be designed, considering efficiency and quality of surgical protocol. Software tools may be used to extract the geometry of customized prostheses from the medical images of the patient; carry out design, analysis, prototyping and manufacture of the (Figure presented) prosthesis; study prosthesis implantation protocols; train the surgeons; and educate the patients. © Springer 2008.