MONITORING THE INTEGRITY OF THE CEMENT-METAL INTERFACE OF TOTAL JOINTCOMPONENTS IN-VITRO USING ACOUSTIC-EMISSION AND ULTRASOUND

Debonding of the cement-metal interface of cemented femoral components of total hip arthroplasty has been shown from clinical and autopsy ma terial to be a common occurrence. Experimentally debonding has been sh own to increase markedly the strains in the adjacent cement mantle. St udies of autopsy-retrieved specimens demonstrate that debonding of the cement-metal interface is a key initiating event in loosening of ceme nted femoral components of total hip arthroplasty. However, both the r adiographic and autopsy evidence of cement-metal interfacial debonding exist after the fact, that is, after debonding has occurred. The lack of prospective data showing that debonding does indeed occur under ph ysiologic loading and occurs prior to other forms of failure of fixati on leaves uncertain the issue of debonding and its role in initiating loosening of cemented femoral components. Knowing when, where, and to what extent the cement-metal interface debonds is critical information in understanding the process of loosening of cemented femoral compone nts. Such information would contribute to improving the durability of stems and improving cementing techniques. In this study, the two nonde structive techniques of acoustic emission and ultrasonic evaluation of the cement-metal interface of cemented femoral stems of total hip art hroplasty were combined to investigate when, where, and to what extent cement-metal debonding occurred in vitro in simulated femurs loaded p hysiologically in fatigue in simulated single-leg stance. Debonding of the cement-metal interface of a cemented femoral component in this mo del was both an initiating event and a major mechanism of compromise o f the cement-metal interface. Additional acoustic emission signals aro se from cracks that developed in the cement.