Effect of weight‐bearing on bone‐bonding behavior of strontium‐containing hydroxyapatite bone cement

Abstract The purpose of this study was to investigate and compare the chemical composition and nanomechanical properties at the bone‐cement interface under non‐weight‐bearing and weight‐bearing conditions, in order to understand the effect of weight‐bearing on the bone‐bonding behavior of strontium‐containing hydroxyapatite (Sr‐HA) cement. In one group, Sr‐HA cement was injected into rabbit ilium (under non‐weight‐bearing conditions). Unilateral hip replacement was performed with Sr‐HA cement (under weight‐bearing conditions) in the other group. Six months later, scanning electron microscopy (SEM) with energy‐dispersive X‐ray (EDX) analysis and nanoindentation tests were conducted on the interfaces between cancellous bone and the Sr‐HA cement. The nanoindentation results revealed two different transitional behaviors under different conditions. nder weight‐bearing conditions, both the Young modulus and hardness at the interface were considerably higher than those at either the Sr‐HA cement or cancellous bone. On the contrary, under non‐weight‐bearing conditions, both the Young modulus and hardness values at the interface were lower than those at the cancellous bone, but were higher than the Sr‐HA cement. In addition, EDX results showed that the calcium and phosphorus contents at the interface under weight‐bearing conditions were considerably higher than those under non‐weight‐bearing conditions. The differences in chemical composition and nanomechanical properties at the cement‐bone interface under two different conditions indicate that weight‐bearing produces significant effects on the bone‐bonding behavior of the Sr‐HA cement. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2007