Bone Damage Evolution Around Integrated Metal Screws Using X-Ray Tomography - in situ Pullout and Digital Volume...

Area of Science:

• Biomedical Engineering
• Materials Science
• Orthopedics

Background:

• Assessing the mechanical integrity of the bone-implant interface is vital for reducing implant failure.
• Local bone deformation around metallic implants under load influences mechanical resistance.

Purpose of the Study:

• To investigate the local deformation and failure mechanisms of bone around titanium implants under physiological loading.
• To evaluate the relevance of an in situ microtomography and Digital Volume Correlation (DVC) model for studying bone-implant interactions.

Main Methods:

• Osseointegration of titanium screws into rat tibiae for 4 weeks.
• In situ screw pullout testing under x-ray microtomography with simultaneous mechanical data acquisition.
• Analysis of tomographic images using Digital Volume Correlation (DVC) to determine internal displacement and strain fields.

Main Results:

• A repeatable failure pattern was observed, characterized by a ∼300-500 μm bone envelope detaching from the trabecular structure.
• Fracture initiated near the screw tip and propagated along the implant surface, influenced by the surrounding bone microstructure.
• DVC identified crack formation in the tibial plateau and localized high strain regions, revealing subsurface damage not visible in standard images.

Conclusions:

• The in situ loading and DVC methodology is a powerful tool for studying internal bone deformation and fracture behavior near implants.
• The observed failure pattern provides insights into the mechanical behavior of the bone-implant interface.
• Understanding these failure mechanisms can inform the design of improved surgical implants and guide pharmacological interventions.