Compare lumbar plexus block (randomized)~ropivacaine 0.475%, 0.4 ml/kg~saline 0.4 ml/kg . Each group includes 30 patients.~Block performed preoperatively.~Surgery under general anesthesia (sufentanil, propofol, atracurium ; maintenance : sevoflurane and nitrous oxide in O2. Sufentanil added peroperatively as clinically needed.~Postoperative evaluation of pain (VAS, by an independant blind observer) as first endpoint, and also morphine consumption via PCA device.~Adverse effects (nausea, vomiting, etc) recorded~Follow-up : 24h. Expectation : sizeable reduction of pain with block, of duration.
Compare lumbar plexus block with ropivacaine 0.475%, 0.4 ml/kg to saline. Each group randomized, includes 30 patients. block performed preoperatively Surgery under general anesthesia. Postoperative evaluation of pain (VAS) as first endpoint, and also morphine consumption via PCA device. Follow-up : 24h.~Expectation : sizeable reduction of pain with block, of duration.