# Biomechanical Performance of the Cemented Hip Stem with Different Surface Finish
###### Abstract  
The integrity of the cemented fixation interface is responsible for the long-term longevity of artificial hip prostheses. Metallic stems with roughened surfaces are considered to provide stronger adhesion with cement. However, clinical studies have reported that roughened stems show a lower survival rate than polished stems. These studies clearly reveal that the causes of artificial stem loosening are very complicated and multifaceted. Therefore, this study was conducted to investigate the mechanical effect of stem surface finish in cemented hip replacement. To accomplish this, a series of cement-metal specimens were tested configurations to assess the mechanical characteristics of the cement-metal interface specimens. A finite elemental model of cemented femoral prostheses was then created, in which the cement-stem interface was assumed to be in different bonding states according to the experimentally measured interface properties. The failure probabilities of the cement mantle and cemented interface under physiological loadings were evaluated. Experimental results indicate that the polished metal produced higher interfacial tensile and lower shearing strengths than the roughened metal. The polished stems were predicted to induce a lower failure probability of cement mantle and higher integrity of the cement-stem interface when compared to the roughened stem. Overall, current results provide significant evidence to support the clinical outcomes of cemented hip prostheses with different stem surface finishes. a pacs: 03.65.-a, 03.65.-a, 03.65.Hk, 03.65.Hk, 03.  
have been shown to improve in response to the surface finish of metallic stems under experimental configurations, the clinical effects of stem surface treatments in orthopedic applications have been controversial with regard to mechanical failure of femoral prostheses. Various treatments of the outer surface of the metal prosthetic stem, including surface polishing, proximal porous coatings, and roughening of textures by grist-blasting, have been employed to enhance the ability of these prostheses to bond with cement [6; 7; 8]. Interfacial strengths have been characterized in the tensile or shearing loading modes under different testing configurations [9; 10; 11; 12; 13]. For example, the push-off or pull-out testing configuration has been used to measure the shear strength of the interface. These methods have enabled the identification of potential factors influencing bonding strength. The interfacial shear strength has been shown to increase with increasing surface roughness of the metal stem [12; 13]. However, the relationship between tensile bonding strength and surface morphology cannot be confirmed owing to the inconsistent results obtained from different experiments [12; 13; 14]. On the other respect, total hip replacement (THR) using either smooth or rough femoral stems has resulted in good performance, as assessed during intermediate postoperative periods [15; 16; 17]. However, the roughened stems were found to induce higher debonding rates at the cement-prosthesis interface [2; 18; 19]. Comparative studies have also reported that roughened prostheses were more susceptible to aseptic loosening than polished stems [20]. Contrarily, primary THR with a cemented polished stem was verified to show excellent results in young patients [21]. Clinical studies relating to cemented implants reported polished tapered stems had a significantly lower revision rate of femoral revision when compared with matt surface stems [22]. Although the causes of the loosening after implantations vary considerably, the continuous fetting wear at the stem-bone-cement interface has been regarded as a type of wearing mechanism causing the failure of the arthroplasty with both matt and polished cemented stems [23]. The influence of surface processing on the tribocorrosion at the cemented interface have been reported in studies [9; 24; 25],for example, [PERSON] et al.