Optimization of electric field parameters for the control of bone remodeling: exploitation of an indigenous mechanism for the prevention of osteopenia.
The discovery of piezoelectric potentials in loaded bone was instrumental in developing a plausible mechanism by which functional activity could intrinsically influence the tissue's cellular environment and thus affect skeletal mass and morphology. Using an in vivo model of osteopenia, we have demonstrated that the bone resorption that normally parallels disuse can be prevented or even reversed by the exogenous induction of electric fields. Importantly, the manner of the response (i.e., formation, turnover, resorption) is exceedingly sensitive to subtle changes in electric field parameters. Fields below 10 microV/cm, when induced at frequencies between 50 and 150 Hz for 1 h/day, were sufficient to maintain bone mass even in the absence of function. Reducing the frequency to 15 Hz made the field extremely osteogenic. Indeed, this frequency-specific sinusoidal field initiated more new bone formation than a more complex pulsed electromagnetic field (PEMF), though inducing only 0.1% of the electrical energy of the PEMF. The frequencies and field intensities most effective in the exogenous stimulation of bone formation are similar to those produced by normal functional activity. This lends strong support to the hypothesis that endogenous electric fields serve as a critical regulatory factor in both bone modeling and remodeling processes. Delineation of the field parameters most effective in retaining or promoting bone mass will accelerate the development of electricity as a unique and site-specific prophylaxis for osteopenia. Because fields of these frequencies and intensities are indigenous to bone tissue, it further suggests that such exogenous treatment can promote bone quantity and quality with minimal risk or consequence.
Rubin
C T
CT
Department of Orthopaedics, State University of New York, Stony Brook.
Donahue
H J
HJ
Rubin
J E
JE
McLeod
K J
KJ
D000818:Animals; D001851:Bone Diseases, Metabolic / Q000517:prevention & control*; D016723:Bone Remodeling; D001862:Bone Resorption / Q000517:prevention & control; D004558:Electric Stimulation; D004574:Electromagnetic Fields; D006801:Humans; D066298:In Vitro Techniques