The Journal of Bone and Joint Surgery, Vol 74, Issue 6 920-929, Copyright © 1992 by Journal of Bone and Joint Surgery, Inc
The effect of low-frequency electrical fields on osteogenesis
KJ McLeod and CT Rubin
Department of Orthopaedics, School of Medicine, State University of New York, Stony Brook 11794-8181.
An in vivo animal model of disuse osteopenia was used to determine the
osteogenic potential of specific components of electrical fields. The
ability of a complex pulsed electrical field to inhibit loss of bone was
compared with the remodeling response generated by extremely low-power,
low-frequency (fifteen, seventy-five, and 150-hertz) sinusoidal electrical
fields. The left ulnae of thirty adult male turkeys were functionally
isolated by creation of distal and proximal epiphyseal osteotomies and then
were exposed, for one hour each day, to an electrical field that had been
induced exogenously by means of magnetic induction. After a fifty-six-day
protocol, the remodeling response was quantified by a comparison of the
cross-sectional area of the mid-part of the diaphysis of the functionally
isolated ulna with that of the intact contralateral ulna. Disuse resulted
in a 13 per cent mean loss of osseous tissue, which was not significantly
different than the 10 per cent loss that was caused by disuse treated with
inactive coils. Exposure to the pulsed electrical fields prevented this
osteopenia and stimulated a 10 per cent mean increase in the bone area. The
osteogenic influence of the sinusoidal electrical fields was strongly
dependent on the frequency; the 150, seventy-five, and fifteen-hertz
sinusoidal fields, respectively, generated a -3 per cent, + 5 per cent, and
+ 20 per cent mean change in the bone area. These results suggest a tissue
sensitivity that is specific to very low-frequency sinusoidal electrical
fields, and they imply that the induced electrical fields need not have
complex waveforms to be osteogenic. Since the frequency and intensity range
of the sinusoidal fields producing the greatest osteogenic response are
similar to the levels produced intrinsically by normal functional activity,
these results support the hypothesis that electricity plays a role in the
retention of the normal remodeling balance within mature bone.