A Vital Microscopic Description of the Effects of Electrical Stimulation of Bone Tissue

Abstract

An implantable, titanium, optical chamber that allows vital microscopic observations of bone tissue during continuous electrical stimulation is described. Tissue reactions to direct current stimulation of a defined bone tissue compartment may be repeatedly observed and recorded on film for indefinite follow-up periods. In this study 5, 20 or 50 μA direct current were applied to chambers inserted into the rabbit tibia. The bone tissue was found to increase in volume after stimulation with 5 and 20 μA, while 50 μA caused bone resorption. Fat-cell concentration was independent of the current levels as used in the present study. Vital microscopy revealed no signs of acute microvascular alterations in the hours following onset of the current. Over an eleven-week follow-up, vessels close to bone borders were found to increase in size from 15–25 microns to 30–50 microns, independent of the level of stimulation. The amount of vessels increased after stimulation with 5 and 20 μA, while in the 50 μA group the vessels decreased to 50% or less of the vascular density observed before start of the stimulation.