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.