The aim of this study was to compare the intraoperative and the postoperative analgesic effect of psoas compartment block (PCB) and supra-inguinal fascia iliaca compartment block (SFIB) in pediatric patients undergoing developmental dysplasia of the hip

All subjects after entering operation room will be connected to standard monitor electrocardiograph, non-invasive blood pressure, heart rate, oxygen saturation.

Three mg/kg of propofol, 0.2 μg/kg of fentanyl and 0.1 mg/kg midazolam will be used for sedation. Oxygen at the concentration of 100% will be administrated under the mask in all patients after satisfactory sedation, tracheal intubation will be performed after intravenous anesthesia with administration of 3 mg/kg of propofol, 0.6 μg/kg of fentanyl and 0.9 mg/kg of rocurium. After intubation 2-3% of sevoflurane and 0.2-0.3 mcg/kg/min of fentanyl will be used to maintain anesthesia guided by PSI and hemodynamic monitoring.

The two groups will receive nerve block with local anesthetics. In the SFIB group, the patients will receive ultrasound-guided SFIB, while the patients in the PCB group will receive PCB under the guidance of ultrasound.

Local anesthetic 0.25% Ropivacaine will be used at 1 ml/kg for SFIB and PCB. (the dose of local anesthetic for SFIB or PCB was not more than 35ml). All blocks will be performed by the same experienced anesthesiologist.

Inclusion Criteria:

• Patients undergoing undergo acetabuloplasty
• Anesthesiologists (ASA) physical status of I to II

Exclusion Criteria:

• Known allergy to local anesthetic
• Infection at the block site.