Effect of metal surface topography on mechanical bonding at simulated total hip stem-cement interfaces

Bonding and loosening mechanisms between bone cement and joint prostheses h ave not been well identified. In this study, the effects of simulated hip s tem surface topography on the interfacial shear strength were examined. Six different surface topographies were used. They were described by several s urface characterization parameters that may directly relate to the interfac ial bonding strength: average surface roughness R-a, root mean square slope R-Delta q, correlation length beta, and fluid retention index R-ri. The sh ear strengths between Palaces E bone cement and stainless steel rods were m easured using an Instron materials testing machine. We found that cement ca n "flow" into the surface microtopography and establish good contact with t he metal surface, The results show that the interfacial strength increases monotonically with the increase of R-Delta q, instead of with R-u. The rela tionship between interfacial strength and surface parameters shows Bat a me tal stem with an isotropic surface texture, higher R-Delta q, and greater R -ri gives a higher interfacial strength. (C) 1999 John Wiley & Sons, Inc.