Epidermal and endosteal sources of endogenous electricity in injured canine limbs

Endogenous electricity associated with musculoskeletal injuries was investigated in injured forelegs of anesthetized adult dogs to identify the endogenous sources and to understand their possible role in healing. Voltages and currents in the injury were measured in progressive stages ranging from a skin incision to an osteotomy of the radius. A circuit model was then developed for the injured limb, and the injury potentials and injury currents were deduced from the measured results. The skin injury activated an epidermal battery (17-42 mV) and bone injury activated an endosteal battery (15-56 mV), both of which drove currents into the injury. The return flow of these currents away from the injury site were along the subdermal soft-tissue surface (10-32 mu A) and periosteal bone surface (8-23 mu A) and through the medullary canal (2-7 mu A); there was also a net outward flow of 10-17 mu A through the osteotomy. The epidermal battery was identified as the primary source of the injury currents on the periosteal surface of bone. The currents in the medullary canal and through the osteotomy were primarily due to the endosteal battery.