Impacts on Natural Ecological Systems
Summary
References
Therapeutic Applications
As we described in chapters 2 and 4, after bone was found to be piezoelectric, much effort was
devoted to the study of the possible physiological role of the piezoelectric voltages. In one approach, in
the early 1960's, working with C. Andrew Bassett of Columbia University, we studied bone's
physiological response to an external voltage and found that it stimulated the growth of bone in the
canine tibia (1). Many investigators subsequently confirmed the phenomenon of electrical osteogenesis
using various animal models (2 -7). The general observation has been that currents of 5-50 µamp
promote bone growth; 0.1-5 µamp produce little or no effect, and currents above about 50 µamp
(depending on the animal model and the electrical circuitry) result in necrosis and gross tissue
destruction.
Commencing in the early 1970's, various investigators began applying electromagnetic energy
to patients suffering from orthopedic diseases characterized by the failure of bone to grow normally.
The most frequently treated condition has been the nonunion of the long bone-a condition in which,
following a fracture, the bone fails to heal spontaneously (8). Three principal methods of application of
electromagnetic energy to bone subsequently emerged. In the coil method, a noninvasive technique,
Helmholtz coils were fitted to the exterior of the site to be treated, and electrically driven so that the
time-varying magnetic field induced a bulk electric field with the tissue (9). In the second method, four
stainless steel pins were inserted percutaneously to the treatment site, and a cathodic current was
applied; this treatment was reported to stimulate the healing of fractures (10), and nonunions (11). The
third method, developed in our laboratory, also used a DC cathodic electrode to stimulate healing, but it
employed a silver wire and significantly less current. We used the silver-wire method to successfully
treat nonunions (12) and, with some modification, infected nonunions (13). Some important aspects of
the three principal methods are summarized in table 11.1. Further details, and other techniques of
electrical osteogenesis, are described elsewhere (8).
Table 11.1 The three principal method of clinical osteogenesis. *Peak current density in tissue.
ELECTROMAGNETISM & LIFE - 149