Surgical procedure including hip joint surgery is extremely painful and associated with considerable postoperative pain in children despite the use of systemic opioids.

Caudal block is a common method used for perioperative pain relief in pediatric lower limb surgeries but carries some complications.

Some novel techniques of regional anesthesia were explored including the quadratus lumborum block (QLB), lumbar plexus block, and recently Pericapsular nerve group (PENG) block.

The objective of the current trial is primarily to assess the analgesic efficacy of ultrasound-guided trans-muscular QLB versus ultrasound-guided PENG block in pediatric patients undergoing open hip surgery for developmental dysplasia of the hip (DDH)

During the pre-anesthesia check-up visit, the proposed intervention will be discussed with the eligible participant's parents or caregivers including data about the aim, the advantages, and the expected side effects, and then detailed informed consent will be obtained before recruitment and randomization.

All participants will be premedicated with 0.5mg/kg oral midazolam about 30min before being admitted to the operating room. The routine standard monitoring including electrocardiography (ECG), non-invasive blood pressure (NIBP, oxygen saturation (SpO2), temperature probe, and end-tidal CO2 (EtCO2) will be applied to all participants. Induction of anesthesia will be performed using a face mask with sevoflurane inhalation in oxygen starting with 2% up to 8% till complete loss of consciousness after that peripheral intravenous (IV) line will be secured where fentanyl 1 μg/kg and followed by cisatracurium 0.15mg/kg to facilitate orotracheal intubation. Anesthesia will be maintained by using isoflurane 1.2-1.5% in oxygen air mixture 50%:50% in addition to incremental cisatracurium 0.03mg/kg.

After induction of general anesthesia, the eligible participants will be randomly assigned to one of two equal groups using an allocation sequence which will be generated using permuted block randomization technique and the block size will be variable.

In both interventional groups of participants, the assigned block will be performed after induction of general anesthesia by the same investigator who will have no further role in the study. Surgery will be started about 15 minutes after performing the block.

Fentanyl 1μg/ kg will be administrated in the case of inadequate analgesia which is defined as an increase of heart rate (HR) and/or mean arterial blood pressure (MAP) more than 20% above the pre-operative values. At the end of the surgery, isoflurane will be switched off and extubation will be done after reversal of muscle relaxant with neostigmine 0.05 mg/kg and atropine 0.02 mg/kg where the participants will be transferred to the Post-Anesthesia Care Unit (PACU). Paracetamol (15 mg/kg) will be administered IV every 6 hours in all patients. Postoperative pain will be assessed by FLACC score (Face, leg, activity, cry, consolability). Morphine 0.1 mg /kg IV will be given as rescue analgesia if the FLACC score will be > 3. Postoperative HR and MAP will be recorded postoperatively at 2 h, 4, 8, 12, 24, and 48 hours.

Inclusion Criteria:

• American society association (ASA) physical status class I - II.
• Participants who will be scheduled for an elective unilateral open hip surgery for correction of DDH under general anesthesia

Exclusion Criteria:

• Participants with respiratory disease, renal or hepatic insufficiency.
• Infection of the skin in the puncture area.
• Coagulopathy.
• Allergy against any of the drugs to be used (bupivacaine).
• Neuromuscular disease.
• Obesity (body mass index, BMI >30).
• Previous hip surgery.
• Previous analgesic medication, chronic pain.
• Previously known neurological pathologies or central nervous system disorders