Effects of reinforcements and gamma‐irradiation on wear performance of ultra‐high molecular weight polyethylene as acetabular cup liner in hip‐joint arthroplasty: A review

Improving the wear resistance of ultra‐high molecular weight polyethylene (UHMWPE), the gold standard polymer for acetabular component in hip joint arthroplasty, is the most important challenge in joint arthroplasty. The possible ways that have been approached to this challenge are by: (i) engineering multi‐phase that is, both carbonaceous and noncarbonaceous fillers‐based polyethylene composites, which unite the inherent attributes of each element available in the system. The wear rate of carbonaceous composite is nearly 50% lower (5.11–6.69 × 10 −5  mm 3 /Nm) than that of noncarbonaceous composite (10–12.5 × 10 −5  mm 3 /Nm), thus, recognized as a potential reinforcement, and (ii) coupling gamma‐irradiation, which is a mandated sterilization process, with multi‐phase nanocomposite to understand the free radical‐scavenging effect of fillers and improved interfacial adhesion strength between fillers and matrix. After the exposure of gamma‐rays (50–100 kGy), the free radicals formed by bond breakage in both the reinforcements and the matrix recombine to form covalent/Van der Waals bond in the interface. Thus, dramatical improvement in wear resistance of both types of composites with 2–4 times decreased wear rate is observed compared to that of composites under un‐irradiated condition. However, enhancing the interfacial adhesion between two different phases is a major constraint in the design of UHMWPE composites. Many methods such as functionalization of reinforcements, and irradiation on functionalized UHMWPE composites that can be approached to address this constraint are documented in this review.