Another series of experiments was performed to determine if electricity could augment fracture repair in laboratory animals. The anode and cathode were placed in various configurations in relation to the fracture site in the fibula of a rabbit. Results showed that fracture healing increased only when the cathode was positioned directly in the fracture site. The augmentation of fracture healing by electricity was determined by testing the mechanical integrity of the fracture callus. Although the location of the cathode was critical for the stimulation of fracture healing, the location of the anode was not important; that is, as long as the anode made electric contact and completed the circuit, it made no difference whether it was placed in the bone, on the surface of the skin, or anywhere in between.

Based on these findings, clinical trials were performed in which cathodes delivering 20 µA each were inserted into the nonunion site by two different methods: (1) percutaneous insertion under radiographic control or (2) surgical implantation, using an open procedure. In the percutaneous technique, a battery pack was connected to the portion of the cathodes that protruded externally through the skin. In the invasive method, a very small implantable battery pack was connected to the cathodes and placed into the subcutaneous tissue under the skin. The clinical trials demonstrated promising results that direct current could heal a nonunion in about the same time and with the same rate of success as bone graft surgery.

Continued research over the past several decades on the benefit of electrical stimulation on bone healing has yielded mixed results; however, the overall data are mostly positive. Direct electrical stimulation for treatment of fracture nonunions is still seen, but the most common scenario in which this methodology is utilized is in the nonunion of spinal fusions.