Total Arthroplasty

Total Hip Arthroplasty (THA) is one of the most common joint replacement procedures performed worldwide, with more than one million replacement surgeries occurring every year [1]. The whole hip joint is replaced by an implant which consists of the femoral stem, the femoral head, and the acetabular cup [2]. Consideration must be given to the types of materials that make up these components, as biocompatibility and mechanical properties determine how the implant functions in vivo. The materials used in commercial implants today are Ultra High Molecular Weight Polyethylene, Alumina, and titanium alloys [1]. Ultra-high molecular weight polyethylene (UHMWPE) is a semi- crystalline polymer which is used for the acetabular cup component [3]. UHMWPE has a yield strength of 21 MPa, and ultimate tensile strength of 48 MPa, 350% elongation, and has a low elastic modulus [4]. UHMWPE has a low coefficient of friction, which mimics the properties of a natural hip joint [5], and has a lifespan in the range of 15-20 years [3]. A disadvantage of UHMWPE arises from the wear debris that is generated by the articulation of the femoral head on the acetabular cup, as well as oxidation [1]. The wear debris is responsible for the development of osteolysis [1], the …show more content…
Low density, corrosion resistance, mechanical strength and biocompatibility are important properties of a femoral stem, therefore the most popular alloy used is Ti-6Al-4V [3]. This particular alloy has an elastic modulus of 110 GPa, which distributes the stress uniformly at the bone-implant interface [3]. It has been reported that metal ions from the alloy have been associated with long term diseases [3]. To overcome stress shielding effects, recent research has been focusing on processing techniques to reduce the elastic modulus of the alloy, while retaining high biocompatibility and strength