The aim of the study is to Evaluate of the analgesic effect of ropivacaine in topical use at the thin skin graft donor site.

For Patient needing a thin skin graft < 320 cm2, randomization will be done in 2 groups, one receiving the standard treatment (20 mL of physiologic serum) during the surgical intervention in topical use to recover an alginate dressing (Algosteril)and the other receive 20 mL of Naropein during the surgical intervention on alginate dressing.

The hypothesis of the study is the administration of ropivacaine will decrease the post-operative pain compared to physiologic serum

Inclusion Criteria:

• Patient older than 18 years old
• Patient needing a thin skin graft < 320 cm2 and which is possible on the thigh
• Patient who read the information letter and signed the informed consent
• Patient affiliated at a social security system
• Effective contraceptive method for more than 3 months for women of childbearing age

Exclusion Criteria:

• Contraindication to one of the medicine used (allergy, intolerance, potential drug interaction)
• Treatment by classII or III of analgesics or analgesic dose of aspirin(>500mg per day) at the inclusion or randomization time
• Preoperative EVA>0 at the skin graft donor site on the thigh
• Sensory disturbances of the lower limbs
• Cognitive disturbances not allowing investigations
• Pregnant or lactating women
• People deprived of discernment
• People deprived of their liberty by judicial or administrative authority
• Protected adult (guardianship or trusteeship)