The fretting wear of the stem trunnion of the total hip prosthesis and its influence on the stability

ABSTRACT This work refers to the fretting phenomenon and the fretting wear manifested at the conical trunnion between the stem and the femoral head of the classic hip prosthesis, metal (CoCr alloy – UHMWPE), as additional factor influencing the loss of the prosthesis stability over time. This wear is due to the micro-movement manifested at the conical junction between the stem and the femoral head. It is quite difficult for the fretting to be monitored during the in vivo operation of the prosthesis, but the fretting wear is evident by analyzing the hip prosthesis replaced after the review surgery. No wear residues were highlighted, but only the worn scars produced on the conical trunk of the femoral stem. This investigation focused entirely on the mechanical wear (fretting), which, although significant, appears to be exacerbated by the adverse electrochemical effects, in view of the mechanical coupling of fretting and corrosion. In addition, at present, the information is minimal regarding the micromechanics of the wear residues generation at the trunnion interface. Keywords:total hip prosthesis, trunnion fretting, fretting wear, micro-movement