Computer modeling of neuromodulation in the management of chronic pain

Objective. To compare the technical performance of laminectomy and percutaneous spinal cord stimulation leads with similar contact spacing by computer modeling. Method. Monopolar and tripolar (guarded cathode) stimulation with both lead types in a low-thoracic spine model was simulated using UT-SCS software. Dorsal column and dorsal root fiber thresholds were calculated as well as the area of recruited fibers in the dorsal columns, the rostrocaudal span of recruited dorsal root fibers and the energy consumption at discomfort threshold. Results. Tripolar stimulation is superior to monopolar stimulation in the recruitment of the dorsal columns, a percutaneous lead recruiting a ~15% larger dorsal column area than a laminectomy lead. This difference is reduced when the contact spacing of the lead models is the same. A percutaneous lead with significant wire impedance (140 Ohms) consumes ~115-240% more energy, whereas the same lead with negligible wire impedance consumes ~40-85% more energy. A deterioration of all performance parameters is predicted when a percutaneous lead is placed more dorsally in the epidural tissue. Conclusion. When positioned next to the dura mater, a percutaneous lead has a similar performance (fiber recruitment in the dorsal columns and the dorsal roots) as a laminectomy lead with a similar contact spacing, but a substantially higher energy consumption. The superior clinical performance of the laminectomy lead is most probably due to the difference in volume and insertion technique of the two lead types.