Inclusion Criteria:  removable percutaneous IPS treatment attended interventional radiology outpatient consultations for back pain and NIC, refractory to medical treatment  Exclusion Criteria:  PS positioning included cauda equina syndrome permanent motor deficit, previous spine surgery, spondylolisthesis greater than Meyerding grade I, local or systemic infection and severe osteoarthritis with pronounced osteophytosis or bone bridges