Finite Element Simulations for Investigating the Cause of Catastrophic Wear and/or Failure of Polyethylene Acetabular Cup Liner in Hip Prosthesis

Wear and/or failure of ultra-high molecular weight polyethylene (UHMWPE) component after total joint replacement are major factors restricting the clinical longevity of artificial joints. In order to minimize the wear and failure of the UHMWPE and to improve the clinical longevity of artificial joints, it is necessary to clarify the factors influencing the wear and failure mechanism of the UHMWPE. The generations of catastrophic wear and/or failure of the UHMWPE acetabular cup liner are frequently observed in retrieved hip prostheses. The primary purpose of this study was to investigate the cause of catastrophic wear and/or failure of the UHMWPE liner in hip prosthesis. The authors focused on change in mechanical state of the UHMWPE liner due to contact with metallic component as a factor influencing the wear and failure mechanism of the UHMWPE liner. Contact analyses between the metallic components and the UHMWPE liner by using the finite element method (FEM) were performed to investigate the mechanical state of the UHMWPE liner. It was found that high contact stresses, which exceed the yield stress of UHMWPE, and considerable plastic deformations occurred in the rim of the UHMWPE liner. It was also found that high stress concentrations occurred near screw holes in the acetabular cup and notches in the UHMWPE liner. This study confirmed that change in mechanical state due to contact with metallic component is the cause of catastrophic wear and/or failure of the UHMWPE liner.