Treatment of sciatic denervation disuse osteoporosis in the rat tibia with capacitively coupled electrical stimulation. Dose response and duty cycle.
We determined the dose-response characteristics of a low-voltage, high-frequency, capacitively coupled electrical signal that reverses an established osteoporosis in a rat tibial model with sciatic neurectomy. The electrical signals were delivered by means of stainless-steel gel-coated electrodes. In the first part of the study, the shape (sine wave) and frequency (sixty kilohertz) of the signal were kept constant while the voltage was varied from 0.01 to ten volts, peak to peak. Control osteoporotic and sham osteoporotic animals showed a mean loss of tibial ash weight of 19 and 17 per cent, respectively, twenty-eight days after sciatic neurectomy plus twelve days of no treatment using sham electrodes. Rats that were subjected to 0.25, 0.50, 1.0, 2.5, and 5.0 volts, peak to peak, for twelve days beginning on the twenty-eighth day after sciatic neurectomy all showed mean losses of tibial ash weight that were significantly less than those of the controls. The rats that had a 0.5-volt peak-to-peak signal showed the least mean loss of tibial ash weight (only 6 per cent). We concluded that a capacitively coupled electrical signal, delivered through gel-coated electrodes, can largely reverse an established disuse osteoporosis due to neurectomy in the rat tibia. In the second part of the study, the duty cycles of a sine-wave, sixty-kilohertz, 0.5-volt peak-to-peak signal were varied (12.5, 50, and 100 per cent on), and the wet, dry, and ash weights were determined and compared with those of unstimulated osteoporotic controls. Only the 100 per cent duty-cycle signal was effective in reversing the loss of bone mass in the neurectomized tibiae.