Low magnetic field effects on embryonic bone growth.

Pulsed electromagnetic fields [EMF] and electric fields have been demonstrated to promote osteogenesis and wound healing. Pulsed EMF's have been approved since 1979 by the FDA, and are highly effective in the treatment of non-union fractures. Increased linear growth, cellular proliferation, cAMP and uptake of tritiated thymidine have been documented on short term exposure. Yet the mechanisms and the changes that occur have been difficult to quantify. Fluorescence, light, and electron microscopy were utilized in this study to assess any histological changes in bone. During incubation chick embryos were exposed to magnets oriented in various positions. Controls were oriented similarly using galvanized steel plugs. Field density in the center of the field was measure by a gaussmeter with a transverse probe. Each chick embryo in its magnetic field was isolated from the magnetic fields of others by being encased in a steel box. Intramembranous [calvaria] and endochondral [tibia] ossification were studied. Fluorescent dyes were micropipetted intravascularly at various stages of chick development. The tissues were fixed in methacrylate and stained for histomorphological study.