Optimal currents for electrical stimulation of bone fracture repair: A computational analysis including variations in frequency, tissue properties, and fracture morphology.

Fracture healing happens naturally in most bone break cases. Occasionally prolongation of restoration period or non-union of the fracture may occur, where electrical stimulation has been shown to facilitate bone restoration by stimulating osteoblasts. Despite clinical use, a comprehensive computational model linking the applied currents to the stimulating field in the fracture has been missing. In this paper, we investigate the input current needed to stimulate osteoblasts in a fracture in the human forearm. Optimal current is computed for various fracture configurations, and sensitivity to frequency and inter/intrapersonal variance in dielectric properties are analyzed. Stimulation thresholds at the fracture site are based on detailed review of experimental studies. Our results show that for a 1 mm thick 30° fracture with a 15 Hz sinusoidal field, the input current amounts to a maximum of 3.77 µA. Minimum and maximum required current levels are plotted versus fracture parameters, all of which comply with the ICNIRP standard. Simulation results are supported by several experimental reports. Our model is useful for understanding the effects of various geometrical and electrical factors on clinical outcome, and serves as a theoretical aid in the design of more efficient systems. Bioelectromagnetics. 40:128-135, 2019. © 2019 Bioelectromagnetics Society.