title: Effect of processing, sterilization and crosslinking on UHMWPE fatigue fracture and fatigue wear mechanisms in joint arthroplasty.
abstract: Ultra high molecular weight polyethylene (UHMWPE) has been used as a bearing surface in total joint replacements (TJR) for nearly five decades. This semi-crystalline polymer has extraordinary energetic toughness owing to its high molecular weight and entanglement density. However, it is challenged by a need to offer a combined resistance to fatigue, wear and oxidation in vivo. The processing, sterilization treatment, and microstructural tailoring of UHMWPE has evolved considerably in the past 50 years but an optimized microstructure remains elusive. This review seeks to provide an overview of this processing history to address two primary questions: First, how does microstructure affect fatigue fracture and fatigue wear mechanisms in UHMWPE? And second, can microstructure be optimized to provide resistance to fatigue, oxidation and wear in vivo? Previous literature demonstrates that while crosslinking improves resistance to adhesive/abrasive wear, it also reduces resistance to fatigue crack propagation and fatigue wear by restricting molecular mobility and rendering the polymer more brittle. Crystallinity improves fatigue resistance but generally increases elastic modulus and concomitant contact stresses in vivo. The presence of fusion defects or oxidation reduces further fatigue resistance and enhances fatigue wear. Thus, UHMWPE microstructural evolution comes with trade-offs. Currently there is no singular formulation of UHMWPE that is ideal for all TJR applications.
authors.affiliation: University of California, Berkeley 2121 Etcheverry Hall, Berkeley, CA 94720, United States. Electronic address: ansari.farzana@gmail.com.
authors.forename: Farzana
authors.initials: F
authors.lastname: Ansari
authors.affiliation: Tahoe Fracture and Orthopaedic Clinic, 973 Mica Dr, Carson City, NV 89703, United States.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Ries
authors.affiliation: University of California, Berkeley 2121 Etcheverry Hall, Berkeley, CA 94720, United States.
authors.forename: Lisa
authors.initials: L
authors.lastname: Pruitt
mesh_terms: D019643:Arthroplasty, Replacement; D010084:Oxidation-Reduction; D011095:Polyethylenes / Q000737:chemistry*; D011475:Prosthesis Failure; D013242:Sterilization / Q000379:methods*; D013314:Stress, Mechanical
chemical_list: D011095:Polyethylenes; C111601:ultra-high molecular weight polyethylene
keywords: Crosslinking; Oxidation; Total joint replacement; UHMWPE fracture; Ultrahigh molecular weight polyethylene