ESP block advantages include its simplicity, easy identifiable ultrasonographic landmarks and low risk for serious complications as injection is into tissue plane that is distant from pleura, major blood vessels and discrete nerves. Coupled with the fact that the erector spinae muscle and ESP extend down to the lumbar spine, ESP block was hypothesized to be performed at the level of L4. In a recent case report, ultrasound guided ESP block was successfully performed at L4 transverse process level for postoperative analgesia after total hip arthroplasty. However, confirmation of the efficacy of ESP block in hip replacement surgeries needed more investigation.

This study will be performed in Cairo university hospital. Thirty adult patients of both sexes scheduled for hip replacement surgery under spinal anesthesia will be enrolled in the study.

All patients meeting the inclusion criteria will be randomly assigned to one of 2 groups, 15 per group:

Group E, ESP group (n=15): prior to surgical incision, patients will have ultrasound guided ESP block before spinal anesthesia.

Group C, Control group (n=15): prior to surgical incision, patients will have spinal Anesthesia without ESP block .

Patients will be randomly allocated by a computer-generated table into one of the study groups, the randomization sequence will be concealed in sealed opaque envelopes.

Inclusion Criteria:

• Patients aged from 40 to 65 years old
• Both sexes.
• ASA I-II.
• Undergo hip replacement surgery.
• Body mass index (BMI) from 18 to 35 kg/m2.

Exclusion Criteria:

• Patient refusal.
• Contraindication to regional anesthesia (bleeding disorder, use of any anticoagulants, local infection, etc. )
• BMI > 35.
• Known allergy to local anesthetics.
• ASA III-IV.
• Patients with difficulty in evaluating their level of pain.