Protocol for patient management Preoperative - Anaesthetic room Antibiotics: augmentin 1.2G Sedation with Target Controlled Infusion (TCI) of propofol at plasma level of 0.5μg.ml-1 Spinal anaesthesia with 3.2 ml hypobaric "plain" bupivacaine 0.5% and intrathecal morphine 0.1 mg All regional nerve blocks performed under ultrasound control Femoral block: 15 ml 0.3% levobupivacaine or ropivacaineFemoral perineural catheter inserted by Anaesthetist 5cm in a cranial direction Sciatic block: single injection 12 ml 0.5% levobupivacaine or ropivacaine Obturator block: single injection 6 ml 0.5% levobupivacaine or ropivacaine