Research progress of biomechanics of bone in disuse osteoporosis

Abstract

Disuse osteoporosis is a kind of osteoporosis correlated with movement limitation, disorder or weightlessness which let bone be in the condition of unloading or mechanical stress reduction. And general or local mineral substance reduction and bone loss happen subsequently. When the bone lacunar-canalicular system which is the sensory receptor of osseous tissue af-fected by force, fluid in bone canaliculi flows subsequently. Both of shear force and voltage produced by the flowing fluid act on mi-crofilaments on protuberance of osteocyte. Mechanical signals transfer in the form of electric current among osteoblasts. Mean-while, the microfilaments are affected by force which would be transferred to the whole cytoskeleton through an actin linked to an integrin on the surface of osteocyte membrane. Factors and enzymes physically connected to the cytoskeleton would be deformed. Bone reconstruction will be regulated by chemical reactions produced by the deformation afterwards. However, reduction or lack of force may generate strains less than threshold of bone reconstruction which would affect bone reconstruction process mentioned above. The change of process results in a phenomenon that bone generation can not keep up with bone resorption and disuse osteo-porosis may happen. Common mechanical test methods used in the studies on disuse osteoporosis contain tensile test, compression test, bending test, torsion test, and so on. Many studies present exercise may lead to prevention and treatment of disuse osteoporo-sis through two approaches. One of the approaches is that bone reconstruction mechanism mentioned above affected by force lead to promoting generation of bone tissue. The other one is that bone mineral density is increased in the result of improvement of nerve growth factors secretion, regulation of calcium balance and humoral regulation via exercise. The article is an introduction to mechanism, prevention and treatment of disuse osteoporosis led by mechanical factors in the level of tissue, cell, and molecule. It may provide convenience for researchers in relative fields to understand mechanism, prevention and treatment of disuse osteoporo-sis in the perspective of mechanics.