60 patients undergoing planned one-level posterior lumbar interbody arthrodesis were randomized to study the analgesic effectiveness of a single epidural injection of ropivacaine. Patients received either a 10-mL epidural injection of 0.1% ropivacaine 20 minutes before the skin incision or a control epidural injection of 10 mL of 0.9% saline solution. Outcomes were assessed of the first 48 hours postoperatively and at discharge. Ropivacaine injection provided better early postoperative analgesia and decreased fentanyl consumption within 12 hours, without related complications such as transient motor weakness.