To Assess Analgesia Provided by Continuous Sciatic Nerve Block in Patients With Hypertensive Leg Ulcer

"The first 3 days, analgesic treatments will be provided, as usual, depending on pain intensity (EN \<3/10 : non opioids, EN 3-5/10 : weak opioids, EN\>5/10 : strong opioids).~If NRS is still over 5/10, continuous nerve block will be proposed. Patients will receive ropivacaïne, 5 mL/h during 7 days, with possibility of one bolus before wound care, through a stimulating catheter stimulong sono®.~In association, analgesic treatments will be provided, as usual, depending on pain intensity (as during the first 3 days)."