What results in fretting wear on polished femoral stems

Fretting wear on polished femoral stems has previously been observed in retrieval studies, and it is showing an increasing significance in the overall wear of cemented total hip replacement. However, the initiation and propagation process of this wear has not been fully understood, with shrinkage bumps and micropores in the cement surface being potential participants. In the present study, these two factors are investigated through a finite element analysis to determine which contributed more to fretting wear. A 2D finite element model was created to represent the stem–cement interface, and physiological loading was applied on the femoral stem to simulate the situation during patient walking. The analysis indicated that the functionality of the shrinkage bumps was incidental in comparison with the micropores as the relative micromotion between the femoral stem and the shrinkage bumps was significantly lower than that between the femoral stem and the micropores. Additionally, the influence of micropore size and loading level on generation of fretting wear was further investigated, and an effective method was proposed to retard fretting wear and to improve the survivorship of cemented total hip replacement. This study theoretically validated the potential contribution of the micropores to generation of fretting wear.