The response of the femur to trauma, a foreign body, and a direct electrical current in mice.

The idea that electricity may be used by orthopedists to repair injured and diseased bone and by orthodontists to help straighten crooked teeth is being popularized."' It started when investigators found that piezoelectrical-type potentials are generated in stressed bone."' Areas of bone under compression develop negative potentials, whereas areas under tension develop positive potentials. It has long been known that when a living bone is forcibly bent it will become thicker on the compressed concave side and thinner on the tensed convex side.' Negative potentials that occur where the bone becomes thicker and positive potentials that occur where the bone becomes thinner may or may not be causative factors in the remodeling of the bone. Although the generation of piezoelectrical potentials in stressed bone is not the same as the passage of an exogeneous direct current through unstressed bone, Lavine, et al.' reported significantly more new bone formation in drilled rabbit femurs receiving a direct current than in non-electrically treated drilled femurs. Bassett, et al.7 reported massive production of endosteal bone around every cathode of insulated battery implants in one femur each of 12 dogs. The electrodes projected into the medullary cavity of the femur and a direct current of 10 ,uA or 100 pA was maintained for 14-21 days. They noted an increased cellularity at the cathode during bone formation and felt it was the result of mitoses. Other investigators performed similar experiments using the femur in rabbits and obtained equivocal or negative results." O'Connor, et al.' used detailed directions supplied by Bassett to duplicate his experimente on the dog femur. They found that the cathode did not always have the most bone formation around it. In two dogs it had the least. We performed an experiment on mice that was similar to those above; however, some modifications were made that we felt were improvements in experimental design.