Multiaxial physiological loading generates complex fluid flow and strain patterns in the osteocyte...

Area of Science:

• Biomechanical Engineering
• Cellular Mechanobiology
• Skeletal Biology

Background:

• Osteocytes within bone sense mechanical forces, crucial for bone adaptation.
• Current in silico models often use simplified loading, not reflecting in vivo complexity.
• Fluid-structure interaction (FSI) models are key for studying osteocyte mechanical environments.

Purpose of the Study:

• To compare osteocyte mechanical environments under physiological multiaxial loading versus simplified uniaxial loading.
• To investigate interstitial fluid flow and osteocyte strain patterns in the lacunar-canalicular system.
• To highlight limitations of current simplified models in representing in vivo conditions.

Main Methods:

• 3D osteocyte-scale FSI simulations were employed.
• Experimentally measured human tibia strains from walking/running were incorporated.
• Simulations compared multiaxial physiological loading with uniaxial sinusoidal loading.

Main Results:

• Multiaxial loading produced complex, heterogeneous fluid flow and strains, with significant dendritic strain.
• Uniaxial loading resulted in uniform flow and minimal strain in perpendicular dendrites.
• Physiological loading induced localized recirculation zones amplifying mechanosensitive signals, absent in uniaxial loading.

Conclusions:

• Uniaxial sinusoidal loading is inadequate for modeling physiological osteocyte mechanics.
• Multiaxial physiological loading generates more complex and potent mechanical signals for osteocytes.
• Findings underscore the need for realistic loading conditions in FSI simulations of bone adaptation.