This study is a prospective, single-arm, open label, single center pilot study to confirm the safety of a ultrahigh frequency DRG stimulator in patients with chronic lower limb pain. The actual trial length is 5 days. Pts will be given ultrahigh frequency pulse stimulation, and VAS will be obtained after 3-4 hours of each stimulation.

This study is a prospective, single-arm, open label, single center pilot study to confirm the safety of a ultrahigh frequency DRG stimulator in patients with chronic lower limb pain. The actual trial length is 5 days. An initial eligibility screening within Day -14. Pt admitted to hospital on Day 1. The lead implantation is conducted on Day 2, and the 1st treatment starts after anesthesia recovery (Day 2 T1). If VAS >4 at 4 hours after the 1st treatment, the 2nd treatment will be conducted. VAS will be acquired 4 hours after the 2nd treatment. On Day 3, physical examination and vital signs will be collected. If VAS >4, the 3rd treatment will be provided. One hour after the 3rd treatment, the device will be removed and an X-ray will be taken. Three hours after the removal, VAS will be collected and then the patient will be discharged. VAS will be estimated by phone call on Day 4, and the patient will return to OPD for follow up examination on Day 5. The trial is completed on Day 5 visit.

Inclusion Criteria:

1. Age ≧20 and ≦75
2. Have a symptom of complex regional pain syndrome (CRPS), failed back surgery syndrome (FBSS), lower limb pain with or without lower back pain with a diagnosis related to spinal lesion and pain history of >6 months.
3. Have an average pain score >5 by Visual Analogue Scale (VAS) on inclusion.
4. Has failed to achieve adequate pain relief from prior pharmacologic treatments.
5. In the judgement of the investigator, the subject is an appropriate candidate for the trial procedure
6. The subject is willing and able to comply with the procedure and requirements of this trial.
7. The participant is able to understand and provide informed consent, and has signed their written informed consent in accordance with IRB requirements.

Exclusion Criteria:

1. Have evidence of a mental or psychological condition that affects pain perception and has difficulty/disability performing objective pain assessment, or have previously failed mental or psychological assessments administered by a psychiatrist that may be deemed to indicate the subject's lack of suitability for participation in this study.
2. Subject has exhibited escalating or changing pain condition within the past 30 days as evidenced by Investigator examination.
3. Be on anticoagulant medication with INR >1.5 or platelet count less than 100,000/μL, peripheral vascular diseases (PVDs), visceral pain or uncontrolled Diabetes mellitus (DM).
4. Has had corticosteroid therapy at an intended site of stimulation within the past 30 days.
5. Pain medication(s) dosages(s) are not stable for at least 30 days.
6. Has previously failed spinal cord stimulation therapy.
7. Currently has an active implantable device including ICD, pacemaker, spinal cord stimulator or intrathecal drug pump or subject requires magnetic resonance imaging (MRIs) or diathermy.
8. Has pain only within a cervical or thoracic distribution.
9. Have a current diagnosis of cancer with active symptoms
10. Have a known terminal illness with life expectancy less than one year
11. Have a systematic or local infection
12. Currently has an indwelling device that may pose an increased risk of infection.
13. Be pregnant or breast feeding
14. Have a medical history of drug or alcohol addiction within the past 2 years.
15. Participation in any investigational study in the last 30 days or current enrollment in any trial.
16. Be currently involved in an injury claim law suit or medically related litigation, including workers compensation.
17. Be a prisoner.

Trial duration (4 days)