Subcutaneous Peripheral Nerve Stimulation (PNS) as "Hybrid Stimulation" After Failure of Spinal Cord Stimulation (SCS) to Control the Back Pain Component in Failed Back Surgery Syndrome (FBSS) Patients.(CUMPNS Study)

Inclusion Criteria: * Age ≥ 18 years and ≤ 80 years. * History of FBSS after one or more surgical procedures on the spine, treated with SCS, * Failure of well conducted conservative treatment (drug or non-drug). * Patients implanted with a single-column or multicolumn SCS lead providing significant relief of the radicular pain component. * Persistent failure on the low back pain component despite the efficacy of SCS on the radicular pain component. * Patients with documented residual neuropathic low back pain (DN4, sensorimotor studies, clinical examination, pain characteristics, etc.). * Patients with significant residual low back pain with mean intensity on Visual Analogue Scale (VAS) ≥ 40 mm) despite Conventional Medical Management (CMM) and SCS (mean measure calculated on daily VAS scores on 5 consecutive days). * Positive response to Transcutaneous Electrical Nerve Stimulation (TENS) trial on the back pain component. * Patients understanding and accepting the study constraints. * Patients covered by French national health insurance. * Patients have signed the Informed Consent Form after being provided with clear and honest information about the study. * Absence of active psychosis or serious psychotic history requiring hospitalisation. * Absence of active cancer. Exclusion Criteria: * Age \< 18 years and \> 80 years. * Back pain amenable to further aetiological biomechanical surgery (discogenic pain, spinal instability, spinal deformity, etc.). * Surgical, psychiatric or anaesthetic contraindication to PNS lead implantation. * Negative response to TENS trial. * Absence of signature of the informed consent form. * Patients not covered by French national health insurance. * Subjects requiring closer protection, i.e. minors, pregnant women, nursing mothers, subjects deprived of their freedom by a court or administrative decision, subjects admitted to a health or social welfare establishment, major subjects under legal protection, and finally patients member of a high-risk population. * Women of childbearing age not using effective contraception.