Prospective trial of selective ultrasound-guided obturator nerve blockade for total knee replacement.

INTERVENTION: Selective ultrasound‐guided obturator nerve blockade performed preoperatively (using ropivacaine 37.5‐75mg), in addition to continuous femoral nerve blockade (ropivacaine 75‐150mg) and spinal anaesthesia (isobaric bupivacaine 15‐20mg). Postoperative analgesia provided by femoral nerve local anaesthetic infusion (ropivacaine 16‐24mg/hr), and morphine patient‐controlled analgesia device (morphine 1mg bolus at 5min lockout). CONDITION: Patients undergoing unilateral total knee replacement. PRIMARY OUTCOME: Cumulative morphine requirements. SECONDARY OUTCOME: Block performance time Complications. Cutaneous sensory deficit in obturator nerve distribution. Hip adductor strength Patient satisfaction. Visual analogue pain scores. INCLUSION CRITERIA: Undergoing unilateral total knee replacement. Communicative in English.