Implications of the fretting phenomenon on the stability of the total hip prosthesis - A review

ABSTRACT The paper presents a review of three of the studies undertaken by the authors regarding the implications of the fretting phenomenon that can manifest in a total hip prosthesis, on its stability. Experimental investigations have been made on Ti6Al4V / UHMWPE prostheses with cemented stem Failure to fix the cemented stem of the prosthesis occurred at 2450000 cycles, after which visual inspection was done and photographic recordings were made. Two different conditions were considered for the normal force N between the contact surfaces: constant or proportional to the axial force P. Determination of the stresses induced in the fretting process required the preliminary characterization of the relationship between the friction force F and the axial force P produced during the loading cycles. Hereafter, experimental studies were carried out to detect the early stage when fretting wear of the Ti-6Al-4V alloy, used for the hip prostheses, appears. Wear is a critical aspect for estimating the fretting fatigue. It was taken into account the unanimous finding that the surface roughness of the testing sample has a significant influence on the occurrence and evolution of the fretting scar. Studies were realized on samples of special shape presented in this paper. Keywords: hip implant, fretting corrosion, fretting fatigue, PMMA, Ti6Al4V