This is a prospective 3x3 crossover study with randomized treatment order, comparing the short-term efficacy of conventional-spinal cord stimulation (CON-SCS) with subcutaneous stimulatio, high frequency-spinal cord stimulation (HF-SCS), and Combination Therapy, in patients with chronic intractable back pain (with or without leg pain).

Patients will be preselected for inclusion in this study at the pain management center of Neurocenter of Southern Switzerland, Ente Ospedaliero Cantonale (EOC) Lugano, and will be informed about study-details by a study clinician. After informed consent signature, the participants with chronic intractable back or back and leg pain will be implanted with the stimulation lead(s). The leads are initially connected to an external trial neurostimulator. Patients will be implanted with two epidural leads and two subcutaneous leads. A three weeks trial phase will follow. The first two days after the leads implant will be without stimulation and thereafter alternating stimulation every week will start, randomly ordering the treatments using a Williams design balanced for first-order carryover effects (i.e. incorporating 6 different treatment orders), from:

• 1) CON-SCS with Subcutaneous stimulation
• 2) HF-SCS
• 3) Combination Therapy A patient's favored SCS mode, providing that there is at least 50% reduction in pain intensity on the NRS in the trial phase, will then be implanted and patients will be followed up for 12 months.

Pain intensity and pain medication will be assessed with a pain diary at baseline and during the trial phase and will be furthermore measured after 3, 6, and 12 months after the implantation. Physical functioning, Pain Extent, Patient Global Impression of Change (PGIC), and Satisfaction with stimulation treatment (SST) will be assessed during the trial phase and will be furthermore measured after 3, 6, and 12 months after the Implantable Nerve Stimulator (INS) implantation. The other secondary outcomes will be measured at baseline, and after 3, 6 and 12 months.

Inclusion Criteria:

• 18 years or older at inclusion
• chronic, intractable back or back and leg pain during at least 6 months
• pain intensity of ≥ 5 on a NRS (ranging from 0 to 10)
• previous drug therapy unsuccessful

Exclusion Criteria:

• Psychological disorders
• Coagulation disorders
• Known immune-deficiency