This paper presents a randomized clinical design for evaluating magnetic fields in the consolidation of femoral shaft fractures. The study involved the design and construction of 20 devices (stimulators and placebos) and the development of 3D computer models of stimulated patient's thighs. A total of 64 patients were included in the study. Follow up time was 8 weeks with 1 hour of stimulation a day. The electrical signals estimated in the computer models were magnetic field, current density and voltage for different frequencies and currents. The results revealed 83% consolidated cases, and 7% with nonunion within the stimulation group, and 72% of consolidated cases and 14% with non-union for the control group. The consolidation results of patients who received stimulation were superior in time and number, but were not statistically significant. The values of electrical variables estimated by the computational model were found to be within a range not harmful to the patient (μA/m2, μT, nV).