Ultra-High-Molecular-Weight Polyethylene in Hip and Knee Arthroplasties

Abstract

Ultra-high-molecular-weight polyethylene (UHMWPE) wear and particle-induced osteolysis contribute to the failure of total hip arthroplasty (THA) and total knee arthroplasty (TKA). Highly crosslinked polyethylene (HXLPE) was developed in the late 1990s to reduce wear and has shown lower wear rates and loosening than conventional UHMWPE in THA. The irradiation dose for crosslinking is up to 100 kGy. However, during crosslinking, free radical formation induces oxidation. Using HXLPE in THA, the cumulative revision rate was determined to be significantly lower (6.2%) than that with conventional UHMWPE (11.7%) at a mean follow-up of 16 years, according to the Australian Orthopaedic Association National Joint Replacement Registry. However, HXLPE does not confer to TKA the same advantages it confers to THA. Several alternatives have been developed to prevent the release of free radicals and improve polymer mechanical properties, such as thermal treatment, phospholipid polymer 2-methacryloyloxyethyl phosphorylcholine grafting, remelting, and vitamin E addition. Among these options, vitamin E addition has reported good clinical results and wear resistance similar to that of HXLPE without vitamin E, as shown by short-term clinical studies of THA and TKA. This review aims to provide a comprehensive overview of the development and performance of UHMWPE in THA and TKA.

Updates on Biomaterials Used in Total Hip Arthroplasty (THA)

“…Ultra-high molecular weight polyethylene (UHMWPE) is an engineering polymer that was launched in THA in the middle of the 1960s as a replacement for the unsuccessful PTFE [ 56 ]. It has become the most often used bearing material with ceramic or metallic counter surfaces dedicated to THA [ 32 , 54 , 57 , 58 , 59 ]. The molecular weight of UHMWPE is at least 1 million g/mole, while the degree of polymerization is 36,000 with a crystallinity of 50–55%, according to the International Standard Organization (ISO 11542).…”

“…The molecular weight of UHMWPE is at least 1 million g/mole, while the degree of polymerization is 36,000 with a crystallinity of 50–55%, according to the International Standard Organization (ISO 11542). The American Society for Testing and Materials stated that its molecular weight is over 3.1 million g/mole, while the degree of polymerization is 110,000 and its properties include high wear-resistance, toughness, durability, and biocompatibility [ 17 , 59 , 60 , 61 ].…”

“…It is concerning how often THA fails over time because of wear problems that shorten UHMWPE’s longevity, and the release of polyethylene particles may result in peri-implant osteolysis and aseptic loosening. UHMWPE wear is one of the most serious post-surgical concerns and the development of UHMWPE is essential for prolonging survival time after THA [ 17 , 18 , 56 , 59 , 61 , 62 , 63 , 64 , 65 ].…”

“…Today, the primary problem of the oxidation of UHMWPE has been significantly decreased by replacing the air with gas or low oxygen conditions during radiation. At the same time, in sterilizing methods, wear is controlled by cross-linking [ 59 , 61 ]. Also, in a recent study, Slouf et al [ 56 ] predicted that oxidative degradation will increase once the median lifetime of the UHMWPE liner in vivo increases and a study of Ishida’s group also predicted this [ 66 ].…”

“…In a more recent study, Fransen et al [ 70 ] showed that the mid-term results of using HXLPE liners in association with 36 mm heads are safe. According to property studies, as the irradiation dose increases, the mechanical properties and material’s plasticity decrease with the appearance of free radicals and implant fragility; in addition, increasing cross-link density leads to a reduction in propagation resistance [ 54 , 59 , 71 ].…”