ABSTRACT

The continuously increasing demand for artificial joint prostheses (Fig. 1.1) [1] represents the composite result of an increasing world population and increasing human average lifetime, as well as a consequence of the changes in our habits and lifestyle. Since people nowadays live longer and get increasingly overweight due to overeating and lack of exercise, eventually the protective tissue lining on the acetabular cup wears away, friction increases, and inflammation, pain, and finally immobilization will result. It should be considered that a healthy average person walks about one million steps per year (with a frequency of about 1 Hz), which results in a walking distance of approximately twice the circumference of the Earth if an average lifetime of 75 years is assumed. During walking, the load on the joints can rise up to two or three times the body weight. This certainly represents an extremely severe engineering performance for any structural material. Total joint replacement might be the only reasonable option to maintain mobility, freedom from pain and hence a rewarding life in old age for those who suff er from joint problems. Furthermore, unfortunately with increasing frequency, younger people require such a surgery because their lifestyle, including aggressive (and

damaging) sports activities, might promote premature wear on their joints. In such cases, a problem arises since younger patients might outlive the average lifetime of the available artificial implants so that a revision surgery might be required, with substantial additional costs, pain, and associated mental stress. However, as mentioned above, nowadays it is an undeniable fact that an increasing fraction of patients will outlive the expected lifetime of artificial joints, which presently can be set to 15~20 years in case of a successful surgery. Consequently, research is continuously ongoing worldwide to provide improved biomaterials with increased mechanical, chemical, biological, and frictional properties, which will result in a longer lifetime in the body environment.