Electrically induced osteogenesis: relationship between charge, current density, and the amount of bone formed: introduction of a new cathode concept.

A study was performed exploring the relationship between charge, current density, and the amount of new bone formed in the medullary canal of the intact rabbit tibia. The results indicate that the amount of bone formed in the vicinity of a cathode is directly related to both current density and charge. Utilizing stainless steel cathodes delivering a constant current of 20 muamps, the optimum current density was found to be 1.06 X 10(3) muamps/mm2 and the optimum charge, 36.29 coulombs. The amount of bone formed with pulsed current approached that formed with constant current only as the total charge delivered by the pulsed current approached that delivered by the constant current. Based on these findings, a new cathode is designed with eight active ports evenly distributed along its length and providing two and one-half times the amount of bone formed by a conventional cathode. This cathode is now in the early stages of clinical evaluation in patients with acquired nonunion.