Theoretical determination of the current density distributions in human vertebral bodies during electrical stimulation

Maxwell´s equations are solved for voltage and current density values at nodal points in a three-dimensional, anatomically based, finite-element grid model of the human trunk constructed from T ₅ to L ₅. Based on the dose response results from the castrated Sprague Dawley breeder rat experiment of C.P. Luessenhop et al. (1987) and the authors´ theoretical determination, the magnitude of the input current to the electrodes necessary to induce a response in the human vertebral body is determined. Four different electrode systems in current clinical use are evaluated, and the optimal input current determined. In addition, the effect of subcutaneous fat is studied.