The use of Spinal Cord Stimulation (SCS) for pain control has already a history of more than 40 years. In SCS, a lead is positioned in the epidural space on the dorsal aspect of the spinal cord so as to produce stimulation induced paraesthesia in the painful area. During the last decades many articles have been published, clearly indicating the effectiveness and safety of SCS with quadripolar leads in the pain management of chronic neuropathic pain, and in particular Failed Back Surgery Syndrome (FBSS). Randomized controlled trials demonstrated that compared with re-operation, SCS provides effective pain relief for at least 3 years and compared with conventional non-surgical neuropathic pain management for at least 2 years.

However, SCS-related complications can occur, that can be divided into surgical complications and hardware complications. The hardware technology has substantially improved over the years. Moreover, electrodes have become smaller in shape and easier to navigate through the epidural space; and finally, internal pulse generators have new programming capabilities and a longer battery life span. All these technological developments led to the application of minimally invasive percutaneous stimulation trials for a variety of patients with chronic neuropathic pain. Turner et al performed a meta-analysis of spinal cord stimulation for failed back surgery syndrome publications and reported hardware complications of 24% lead migration, 7% lead failure and 2% pulse generator failure. While this analysis evaluated studies using older hardware systems, there is first evidence that the rate of these complications is lower currently with new systems. In the recently published PROCESS paper, also using quadripolar electrodes, long term follow-up showed that hardware complications were 14%: lead migration, 3% lead failure and no pulse generator failures.

Generally, patients with radicular pain to the lower extremities respond better to spinal cord stimulation than patients with isolated axial low back pain. However, a few studies have shown that axial low back pain in combination with bilateral leg pain, also respond well to spinal cord stimulation. Both four (e.g. quadripolar Quad lead) and eight (e.g. octapolar Octad® lead) electrodes were shown to be effective in treatment of low back and lower extremity pain, with no apparent advantage of one system over the other. In the recent PROCESS study publication, the reduction of SCS on low-back pain was not-statistically significant when compared to baseline. Even though it seems that eight electrodes may have the potential advantage in case of lead migration or disease progress, no clinical data have been published on the effectiveness of SCS using the octopolar epidural lead. The Octad study is a prospective, multi-center, open-label, non-randomized, interventional study designed to assess the effectiveness and technical performance of SCS with the Octad® lead for treatment of chronic pain. This study is not set up as a comparison study between the Octad lead and other SCS leads, such as the Quad lead, because the Octad lead is used in most eligible FBSS patients as the standard of care lead.