Metallic Biomaterials of Knee and Hip - A Review 1 Trends Biomater. Artif. Organs, Vol 24(1), pp 69-82 (2010) http://www.sbaoi.org Metallic Biomaterials of Knee and Hip - A Review Marjan Bahrami Nasab, Mohd Roshdi Hassan Department of Mechanical and Manufacturing Engineering, Engineering Faculty University Putra Malaysia Received 1July 2009, Accepted 5 September 2009, Published online 27 January 2010. Introduction One of the most significant current discussions in orthopedic is the total joint replacements especially hip and knee and the increasing trend to replace degraded and destroyed biological materials by artificial organs. It is estimated that approximately 1 million hip replacements and 250,000 knee replacements are carried out per year [1]. This number is expected to double between 1999 and 2025 as a result of aging populations worldwide and growing demand for a higher quality of life [2]. Another statistical data estimated that by the end of 2030, the number of total hip replacements will increase by 174% and total knee arthoplasties is predicted to grow by 673% from the present rate [3]. An increasing trend of the number of knee replacements in different countries over the last 10–15 years is shown in fig 1. Yet-increasing demand for implants makes it crucial to accelerate efforts on biomaterials. Unfortunately, the currently used materials have been found to have tendencies to fail after long- term usage due to not fulfilling some vital requirements such as modulus close to that of bone, high wear and corrosion resistance and good biocompatibility. Rimnac et al.[4] investigated the failure of orthopedic implants in three case studies (hip and knee) and illustrated that both material and design deficiencies contribute to failure of total joint replacements. Failure of current biomaterials imposes pain for patient and after some time revision surgery should be performed. The purpose of this paper is to review some recent researches about presently used metallic biomaterials and discuss on great potential of NiTi and porous NiTi shape memory alloys (SMA) for orthopedic implant. Meanwhile this study seeks to address the following questions: 1) When a material is going to be used in the human body, what kinds of requirements should be fulfilled by that material to be considered as a successful biomaterial? 2) What kind of problems can occur if these requirements are not satisfied by the material? 3) Which of the requirements present in the currently used materials and which cannot be fulfilled? 4) What solutions are available for improving the properties which are not completely satisfied by the biomaterials? 5) Do the NiTi and porous NiTi shape memory alloys have necessary requirements to be utilized as a metallic biomaterial for orthopedic implants especially hip and knee? The reminder of this paper is organized as follows; section 2 describes the requirements and general issue about biomaterials. So the two first research questions will be answered in this section. Section 3 will address questions 3-5. Superior properties of these materials will be discussed in section 4. Final section concludes and purposes further works.