Effects of electrical stimulation on the biomechanical properties of fracture healing in rabbits.

One hundred fifteen white rabbits with an average weight of 2.0 kg were used to study the influence of electrical stimulation on osteogenesis. They were divided into three groups: Group I was electrically stimulated with a constant direct current of 20 microamperes delivered to the fracture site; Group II was the control group having the same protocol as Group I except that the stimulator was not switched on; and Group III was the normal fracture healing group (no introduction of electrodes to the fracture site). Roentgenologic and histologic assessment showed that new bone formation in the electrical stimulation group was more exuberant than those in the other two groups in observation periods from three to eight weeks. However, at 12 weeks no difference was observed among the three groups. Biomechanical analysis showed definite increases in the breaking strength and bending stiffness of the fracture healing tibia in Group I, especially at six weeks after surgery. However, at 12 weeks no significant difference was observed among the three groups. Therefore, electrical stimulation of fracture healing has a positive effect only at the midphase of the healing process, and it does not lead to faster fracture healing.