Interaction of ultrasound waves with bone remodelling: a multiscale computational study

Area of Science:

• Biomedical Engineering
• Mechanobiology
• Skeletal Biology

Background:

• Ultrasound stimulation is investigated for its potential to influence bone remodeling and healing.
• Recent reviews question the clinical efficacy of low-intensity pulsed ultrasound stimulation (LIPUS) for bone healing.
• The underlying physical and biological mechanisms of ultrasound's effect on bone repair remain poorly understood.

Purpose of the Study:

• To investigate the effect of LIPUS on cortical bone, focusing on the mechanical stresses experienced by osteocytes.
• To explore the relationship between tissue-scale ultrasound stimulation and cellular-level mechanical stress.
• To understand the role of interstitial fluid flow and wall shear stress in osteocyte mechanotransduction during LIPUS.

Main Methods:

• Computational modeling using the finite element method in Comsol Multiphysics.
• Simulation of interstitial fluid (IF) flow within the lacuno-canalicular network (LCN).
• Assessment of wall shear stress (WSS) levels induced by LIPUS on osteocytes under different LCN permeability values and IF flow models.

Main Results:

• Two distinct IF flow models and LCN permeability values were used to estimate WSS.
• The calculated WSS values varied significantly based on the model assumptions.
• One model yielded WSS estimates consistent with previous bone mechanotransduction studies.

Conclusions:

• The study presents preliminary results from a computational model aimed at elucidating LIPUS mechanisms.
• Understanding WSS on osteocytes is crucial for explaining LIPUS efficacy in bone healing.
• This modeling approach may provide insights into the controversial effectiveness of LIPUS therapy.