In spinal cord stimulation (SCS) clinical practice, longitudinal guarded cathode stimulation by a single lead, placed on the spinal cord midline provides the broadest parasthesia coverage. This study uses a triple lead longitudinal tripole with the center lead placed on the midline. The transversal spacing between the leads is varied to study its effect on the usage range (UR) and the recruited area (both depth and width) of dorsal colums activation