The performance of joint implants is determined by the interplay among designs, materials, manufacturing processes, and the way patients use them. This is similar for many implantable medical devices. Because of the statistical nature of manufacturing processes and human use conditions, the product performance is a statistical function of not only the relevant parameters and their interactions, but also the variations that those parameters can have under the normal processing and use conditions. It has been a goal of many scientists to develop a transfer function to predict the product performance from the properties of materials. Pezzotti’s book represents this effort.
This book begins with a review of joint implants and the common failure modes of each material used in the joints. An introduction to some analytical and characterization methods such as atomic force microscopy, Raman and infrared spectroscopy, cathodoluminescence spectroscopy, and tribology assessments is presented. Detailed descriptions of individual materials are provided next.
Alumina is best for load bearing and wear resistance. The weakness of this material is its brittleness, which is discussed in terms of pores, grain size, and inclusions. Methods to overcome this weakness such as using additives and hydraulic compression are presented. Zirconia has been used successfully for implants, but the phase transition from the tetragonal to monoclinic polymorph has been a problem. The book discusses the methods and mechanisms to inhibit this transition, such as the addition of yttrium oxide. Compounding alumina with zirconia is presented. The use of gamma irradiation to improve the current ultrahigh-molecular-weight polyethylene (UHMWPE) is also detailed. Different methods for treating gamma-irradiated UHMWPE parts for reducing free radicals and therefore improving wear resistance are discussed using products available in market as examples. In addition, using additives such as vitamin E and antioxidants for reducing radiation-induced free-radical oxidation of UHMWPE is described. A free-radical depth profile and correlation with wear properties are presented using Raman spectroscopy and wear test data. In the last chapter, new materials, designs, and testing methods are discussed as future technologies.
Overall, this is a good reference of joint implant research. Extensive literature papers have been cited, though a number of them are by the author. An area of improvement can be to include other important research topics and tools. for example, use of electron spin resonance to monitor free-radical oxidation of UHMWPE.
Reviewer: SuPing Lyuis a Principal Researcher at Medtronic Inc., Mounds View, Minn., USA.
