Metallurgy of Spinal Instrumentation

Abstract

Examination of clinical literature tends to suggest a rather limited diversity of metals used in spinal instrumentation (Netter FH (ed) Atlas of human anatomy, 5th edn. Saunders Elsevier, Philadelphia, 2011; Yoshihara H, Spine J in press, 2013). The American Society of Materials (ASM) Materials and Processes for Medical Devices (MPMD) database shows approximately 33 different alloys used in medicine in the USA. Within this database, only about one-third are used in orthopedic applications, and in the clinical environment, these alloys are generally referred to in very general terms such as titanium, Ti6Al4V, stainless steel A316L, or cobalt-chrome, CoCrMoC. For the purpose of spinal applications, it may be convenient to consider the general alloy systems, ferrous stainless steel, titanium and its alloys, cobalt-chromium, and tantalum. From this standpoint, the characteristics along with their clinical advantages and disadvantages can be discussed. The reader is kindly guided to many excellent texts concerning specific aspects of metallurgy as well as other chapters in this book for details on specific alloy systems and their properties (Yu WD, Oper Tech Orthop 13(3):159–170, 2003; Black J, Biological performance of materials, 4th edn. Taylor and Francis, Boca Raton, 2006; Hosford WF, Physical metallurgy, 2nd edn. Taylor and Francis, Boca Raton, 2010; Narayan RJ (ed) ASM handbook: vol 23, Materials for medical devices. ASM International, Materials Park, 2012; Yahia L (ed) Shape memory implants. Springer, Berlin, 2000). It should be noted based on the following section that for all metals represented herein, in terms of clinical applications, many of the properties discussed have little effect on their selection during surgery as the medical priority is maintaining bony alignment and minimizing patient discomfort.