Investigation on physical exercise-induced interstitial fluid flow in bone tissue to mitigate osteoporosis and disuse bone loss

Osteoporosis and disuse bone loss in elderly individuals, bed-ridden patients, and astronauts are serious health issues. Severe bone loss increases bone porosity and thus decreases bone strength which further promotes bone fractures. Prophylactic exercise is beneficial in preventing bone loss as mechanical loading enhances bone modeling and remodeling activities. Loading-induced fluid flow within the bone tissue is considered as stimulus of excitation of mechanosensory bone cells, i.e., osteocytes, which regulate the osteoactivities related to bone remodeling. In vivo and in silico studies observed that bone loss adversely influences the bone microarchitecture, such as porosity and permeability, which reduces interstitial fluid flow required for the bone remodeling process. Physical exercise-induced mechanical loads on bone may enhance interstitial fluid flow above the osteogenic threshold. Nevertheless, how physiological loading associated with exercise influences interstitial fluid flow in osteoporotic/disused bone tissue is not well established. Thus, the present study computes the interstitial fluid flow in healthy and osteoporotic/disused cortical bone tissue as a function of gait loading waveforms of physical exercise using a poromechanical finite element model. The outcomes indicate that osteoporotic and disused cortical bone tissue with greater porosity and less permeability experience comparatively lower pore pressure and fluid velocity than healthy tissue. Moreover, physiological loading exercise enhances fluid flow in diseased tissue, which is helpful in exciting bone cells for improvement in bone remodeling. Overall, the findings of the present investigation may be beneficial in the design of potential physiological exercises to prevent osteoporotic and disuse bone loss.