The Effect of Subcutaneous Injection of Botulinum Toxin A on Chronic Wound Pain in Lower Extremities

Inclusion Criteria: 1. Age ≥ 18 years old. 2. Lower extremity ulcer ≥ 4 weeks. 3. Ulcer area ≥ 1,5 cm2 and ≤ 20 cm2 4. Patients with neuropathic pain related to the ulcer (daily VAS pain scores ≥ 30 mm at rest and DN4 score ≥ 4). 5. Normal monofilament and vibration test in lower extremities. 6. Patients who can fill out pain diary correctly. 7. Written informed consent to participate in the study after having fully understood the contents of the protocol and restrictions. Exclusion Criteria: 1\. Infection at injection site. 2. Hypersensitivity to botulinum toxin A. 3. Peripheral neuropathy. 3. Diabetic foot ulcer. 4. Unstable critic peripheral ischemia judged by investigator 5. Exposed capsule, tendon, muscle or bone in the ulcers. 6. Tunnelling, undermining or sinus tracts. 7. Disorders of the neuromuscular junction (e.g. Myasthenia). 8. Topical analgesic (e.g Biatain ibu or Lidocain) within 7 days before inclusion. 9\. Pregnant or lactating woman and woman with childbearing potential but does not use contraception. 10\. Judgment by the investigator that the patient is not suited for study participation.