Joints Photo courtesy Joints are those amazing biomechanical structures which allow us to move. They can be very simple, or very complicated. But like all machines, it is the moving parts that are the most susceptible to breaking down. MSE plays an important role in the development of the materials which will be used to manufacture artificial joints. Whether it's the entire joint, or just a part of it needs to be replaced, there are many aspects about the materials that must be addressed. Photo courtesy Replacement knee joint shows use of metals and polymers. For example, the new joint must somehow be connected to the body of the recipient. Also, the new joint itself must must be constructed from materials which will both perform the necessary functions of the joint, and be able to withstand the incredible forces which are placed on it during everyday activity. Depending on the type of replacement and the physiology of the patient, the task of attaching the new joint to the body could involve one of many procedures. Photo courtesy One possibility is to merely cement the piece into the bone which is already there. This is called the Bone-Cement Fixation, and leaves yet more options to consider. In any case, however, finding new materials, or treatments for these materials, helps to increase the longevity and security of the bond. In another case, the external surface of the artificial joint is designed to allow the preexisting bone to grow into and around the new material. Porous Ingrowth Fixation, as this procedure is called, starts with a coating of titanium and calcium hydroxyapatite. Here again, the nature of the replacement can make a difference on the style, and design of the actual materials to be used. And, on the high-tech side of things, new materials are being developed which allow the new joint to actually chemically bond with the preexisting tissues in the patient. Recently, this was accomplished with a glass-ceramic compound, but this is still a very new application of materials science. Site related questions or comments? Contact crc@tms.org