Shear Stress Within Trabecular Bone Marrow due to Low Magnitude High Frequency Vibration

Low magnitude high frequency (LMHF) loading is anabolic to bone. LMHF loading for one year resulted in a 32% increase in the trabecular bone volume, decreased trabecular spacing and increased trabecular number in a sheep model (1). In contrast, no change was seen in cortical bone, suggesting the anabolic effect is limited to the trabecular compartment. Rats subjected to 90 Hz vibration developed greater trabecular bone volume and thicker trabeculae than rats subjected to vibration at 45 Hz (2). However, the strain induced in the bone during the 90 Hz vibration was significantly lower than during the 45 Hz vibration, indicating that the effect does not depend on matrix strain. As such, shear stress in the marrow may be the anabolic signal in this loading regimen.