Intramedullary Pressure Induced by Dynamic Hydraulic Stimulation and its Potential in Attenuation of Bone Loss

INTRODUCTION: Bone fluid flow has been demonstrated as a critical regulator in mechanotransductive signaling and bone adaptation. Intramedullary pressure (ImP) is suggested to initiate bone fluid flow and influence the osteogenic signals within bone. The potential ImP-induced bone fluid flow then triggers the remodeling process in the skeleton . It has been demonstrated that ImP generated by oscillatory electrical stimulations can effectively mitigate disuse osteopenia in a frequencydependent manner in a disuse rat model [2, . Directly related to translational potentials of ImP, a non-invasive method that couples external stimulation and internal bone fluid flow remains challenge. Therefore, it was hypothesized that noninvasive dynamic hydraulic stimulation (DHS) can induce ImP with minimal strain and initiate adaptive responses in vivo to elicit osteogenic activity. The objectives of this study were: 1) to demonstrate the effects of a novel, non-invasive dynamic external pressure stimuli (3Hz) on bone structural properties in a disuse model; and 2) to evaluate the immediate effects on ImP and bone strain induced by the stimuli over a range of frequencies.