Characterization of Biomaterials

Book excerpt: In joint replacement surgery with suboptimal bone, allograft materials are often used to achieve biological fixation of the metallic implant to the host bone and reducing the implant fixation time. The most commonly used techniques are cemented and hydroxyapatite (HA)-coated metallic implants. Typically, HA coatings are suggested for patients with better bone stock, whereas recommended implant fixation process for most other osteoporotic patients is bone cements. In general, there is a long-standing need to improve the performance of hip and other devices for longer in vivo implant lifetime that can help in reducing the number of revision surgeries, as well as minimizing physical and mental trauma to the patient. To achieve these goals, it is important to understand the mechanical and biological properties of coatings that can influence not only its short- and long-term bioactivity but also life span in vivo. Over the years, it has been recognized that the stability of a coated implant is governed by its physical and mechanical properties. A coating that separates from the implant provides no advantage over an uncoated implant and undesirable due to problems with debris materials, which can lead to osteolysis. Therefore, it is important to properly characterize the coated implants in terms of its physical and mechanical properties. In this chapter, specific details on coating characterization techniques including sample dimensions, sample preparation, experimental procedure and data interpretation are discussed. In particular, the standards and requirements of regulatory organizations are presented elucidating the significance and use of each characterization. It is important to appreciate that mechanical properties of coatings can only be determined with certain coating specification such as coating thickness. This chapter is designed even for non-experts to follow mechanical property characterizations of coatings on medical implants.