Management of postoperative pain is critical in the pediatric patients, however, safe and effective analgesia for pediatric surgical patients remains a challenge. Preemptive analgesia is based on preventing a prolonged change in central nervous system function by blocking afferent input before the surgical stimulation may evoke central sensitization and aggravate amplification and prolongation of postoperative pain. However, the clinical efficacy of preemptive analgesia is still controversial. In this study, the investigators aim to assess the impact of preemptive epidural analgesia on postoperative pain in pediatric patients for corrective osteotomy of the lower extremities expecting severe postoperative pain.

Inclusion Criteria:

• Pediatric patients (3-12 years of age) scheduled for corrective osteotomy of the lower extremities
• ASA class I and II

Exclusion Criteria:

• Coagulopathy
• Neurological disease
• Allergy to local anesthetics or contraindication to use of ropivacaine
• Infection at the site of epidural catheter insertion