Failure behaviour of rat vertebrae determined through simultaneous compression testing and micro-CT imaging.

Area of Science:

• Biomechanical Engineering
• Orthopedics
• Materials Science

Background:

• Skeletal fractures, particularly osteoporosis-related ones, incur substantial healthcare and societal costs.
• Previous studies on bone failure mechanisms often overlooked the cortical shell's role, focusing solely on trabecular bone.
• Understanding vertebral fracture mechanics is vital for developing effective treatments and preventative strategies.

Purpose of the Study:

• To investigate the progression of compressive failure in rat vertebrae using simultaneous micro-computed tomography (micro-CT) imaging and incremental compression testing.
• To identify distinct failure modes and their association with anatomical features and disease states.
• To elucidate the combined contribution of cortical and trabecular bone to vertebral failure.

Main Methods:

• Incremental compression testing was applied to rat vertebrae across different disease states (healthy, osteoporotic, osteoporotic + treatment).
• Simultaneous micro-CT imaging was utilized to visualize the real-time progression of fracture.
• Failure modes were analyzed and categorized based on their initiation and propagation patterns.

Main Results:

• Three distinct failure modes were observed in all tested vertebral specimens, irrespective of disease state.
• Two prevalent failure modes (Types I and II), present in 93% of specimens, were linked to vascular apertures on the dorsal and ventral surfaces.
• These failure modes are likely driven by stress concentrations at the cortical shell's apertures and adjacent reduced trabecular bone volume.

Conclusions:

• The study demonstrates that vascular apertures play a critical role in determining vertebral fracture patterns.
• Both the cortical shell and trabecular bone significantly influence the compressive failure behavior of rat vertebrae.
• Future research on bone fracture mechanics should integrate the biomechanical contributions of both cortical and trabecular bone structures.