Today the nerve stimulation technique is the most prevalent technique to introduce catheters for peripheral nerve blocks. The success rate for postoperative analgesia after foot and ankle surgery with popliteal catheters is variable - typically 70% in our department. The patients with catheter failure have severe postoperative pain, high opioid dosages, cognitive blurring, nausea, vomiting, reduced ambulation, increased surgical stress response and increased morbidity. Pain problems and adverse effects prolongs postoperative observation time and maybe also time to discharge.