Periprosthetic bone resorption. Particles versus movement.

Using a rat model, we created a bone-to-titanium interface and applied phagocytosable high-density polyethylene particles between the bone and implant, either initially or when the interface had matured. No fibrous membrane developed and no bone resorption was found. If sliding movements were initiated at the interface after two weeks, there was formation of a fibrous membrane. The additional application of particles did not change the thickness of the membrane, and there were only minor qualitative changes. Creation of a membrane by movement followed by cessation of movement and the application of particles caused the membrane to persist, whereas in a particle-free control group bone-to-metal contact was re-established. Our findings suggest that mechanical stimuli are of primary importance for prosthetic loosening, and that particles may modulate the later stages of the loosening process.