Date of Award

2-1-1992

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Physiology and Pharmacology

Abstract

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 have been difficult to quantify. Little has been published in the literature about the effects of a magnetic fields upon bone growth. Parkinson (1985) indicated a system at rest has no magnetic force acting upon and movement due to thermal energy is small enough to be ignored. However, Bruce, Howlett and Huckstep (1987) applied a static magnetic field of 220 to 260 gauss to radius fractures in adult rabbits. A significantly greater force was required to break the healed fracture (p $<$ 0.01) than control fracture. We have decided to investigate the effects of a lower dosage magnetic field upon embryonic bone growth, to assess if a magnetic field could possibly be a useful non-invasive technique of healing nonunion fractures.Fluorescence and light microscopy were utilized to assess histological changes in bone. During incubation chick embryos were exposed to magnets oriented in various positions. Controls were oriented similarly using steel plugs. Field density in the center of the field was measured with a gaussmeter. Each chick embryo in its magnetic field was isolated from the others by being encased in a steel box. Intramembranous and endochondral ossification were studied. Fluorescent dyes were micropipetted into the amniotic cavity of the chick embryo at various stages of development. At the fourteenth day of incubation, the animal was sacrificed and bone tissues excised. The tibias and femurs were measured with a caliper. The tissues were fixed in 10% formalin, embedded in methacrylate, sectioned and stained for histological study.Data analysis indicated a significant difference (p $<$ 0.05) in the developmental stage due to low dosage static magnetic field. Small sample size and variation within groups indicated that more research is needed. Methods and materials were specific and replicable. No background auto-fluorescence was observed on specimens examined under the fluorescence microscope.

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