Accelerated Bone Growth Remotely Induced by Magnetic Fields and Smart Materials

Bone structure is exquisitely matched to its physical loading environment. From the cartilaginous skeletal framework formed in the embryo to the aging skeleton, bone architecture is directly related to function. Bone is a dynamic system, constantly remodeling itself by absorbing old tissue and forming new tissue. This capability allows bone architecture to become optimized to the loading environment. Julius Wolff [1] first postulated that bone structure adapts to changing stress environments in 1892. Exact understanding of the process of mechanotransduction, however, has remained elusive. In addition to normal remodeling, bone growth has been shown to occur along the diaphysis, or shaft portion, of long bones such as the femur when placed in dynamic bending. Bone in this region is dense and is known as cortical bone. A bending moment placed on a long bone will cause the bone to curve creating a region of tension on one side and a region of compression on the opposing side. As the bending moment is cycled, fluid within the bone will flow from the region of compression to the region of tension creating fluid shear on cell walls within the bone which promotes the anabolic response of growth [2]. Growth from such stimuli is thought to be mediated by fluid flow around quiescent bone cells, osteocytes, and their canalicular process coursing through the bone structure [3]. Growth in this manner is directed in a latitudinal direction creating a thicker and stronger diaphysis.