Abstract :

This investigation continues to explore the effects of applied electrical potentials on the enhancement of bone healing. The approach is to mimic the known piezoelectric production in bone and apply external elctrical forces within the range of 2 to 5 mu/amp at 0.5 volts. The work seeks to determine the intrinsic electrical properties of bone. The resistance has been measured for rabbit femora under a variety of physiological conditions. The resistance in rabbit femora was 2 to 5 x 10 to the 5th power ohms. This resistance did not vary much until after the bone was removed from the rabbits. In a human subject the resistance of the tibia was 1.5 x 10 to the 5th power ohms. The work continues to obtain information at the cellular level during electrical stimulation of bone healing comparable to its unstimulated controls. Tritiated thymidine is used as an indicator of mitotic activity. The autoradiographs have demonstrated that cells in the healing region are present in distinct pockets. This suggests that these cells which are preparing or undergoing mitotic activity are reproducing in situ. Also investigations determine the electrical enhancement of bone healing as indicated by collagen formation and calcification dynamics. Electron microscopic investigations are used to determine the actual cellular dynamics. The electrical stimulation method is being used to alleviate difficult and selected "test" cases of congenital pseudarthrosis in humans.