Background:

In recent years, regional anesthesia has become more popular because it can reduce pain and the need for strong pain medications like morphine. For hip surgery, the PENG block is already known to be effective. A newer method, called the iliopsoas plane block (IPB), is very similar and has also shown good results in hip arthroscopy. However, these two techniques have never been directly compared in patients undergoing hip replacement surgery using the posterior approach.

Goal:

This study aims to see if the IPB is just as effective as the PENG block for controlling pain and helping patients recover well after hip replacement surgery.

Method:

118 adult patients scheduled for hip replacement under spinal anesthesia will be randomly assigned to receive either: IPB: 7 ml of Ropivacaine 7.5 mg/ml PENG: 14 ml of Ropivacaine 3.75 mg/ml Both injections are given under ultrasound guidance 30 minutes before spinal anesthesia. Neither the patient, the surgeon, nor the data collector will know which technique was used.

Post-Surgery Care:

All patients will receive standard pain relief, including:

Paracetamol every 6 hours Etoricoxib once a day Morphine via a patient-controlled pump for 48 hours

Main Outcome Measured:

The primary goal is to compare pain during movement 6 hours after surgery, using a pain scale from 0 (no pain) to 10 (worst pain). The study will consider the two blocks equivalent if the difference in average pain scores is less than 1 point.

Other Outcomes:

Total morphine used in 48 hours Pain scores at rest and during movement at various time points Walking ability (2- and 6-minute walk tests, and timed-up-and-go test) Quality of recovery (using the QoR-15 questionnaire) Side effects of morphine Patient satisfaction Length of hospital stay

Safety:

Both techniques are safe and already used in clinical practice. Ultrasound guidance minimizes risks like nerve injury, bleeding, or infection.

Conclusion:

If the IPB is shown to be as effective as the PENG block, both can be considered reliable options for pain control and early recovery after hip replacement surgery.

This study investigates the comparative effectiveness of two regional anesthesia techniques-the Pericapsular Nerve Group (PENG) block and the Iliopsoas Plane Block (IPB)-in patients undergoing total hip arthroplasty (THA) via the posterior surgical approach. While both blocks have shown promise in managing postoperative pain and minimizing opioid use, direct comparisons between them in this surgical context are lacking.

The PENG block, which targets the articular branches of the femoral, obturator, and accessory obturator nerves, has become increasingly used in anterior and lateral hip surgeries. The IPB, though more recently introduced, involves injection in a similar anatomical region and has shown good analgesic results in patients undergoing hip arthroscopy. Given their overlapping targets, these two blocks may offer comparable clinical benefits; however, this has not been validated in THA performed through a posterior approach.

To address this gap, the current randomized, double-blind equivalence trial will compare the two techniques using standardized ultrasound-guided procedures and uniform dosing of ropivacaine adjusted for volume and concentration. All patients will receive the same spinal anesthetic and postoperative analgesia regimen, minimizing confounding factors.

The primary objective is to determine whether IPB provides pain control equivalent to the PENG block during early postoperative mobilization. By assessing patient-reported pain scores, along with recovery quality and opioid use, the study aims to generate evidence that may inform anesthesia planning in joint replacement surgeries and support the integration of newer regional techniques into enhanced recovery protocols.

Inclusion Criteria:

Adult patients (age >18 years) ASA physical status classification I-III Scheduled for elective posterior approach total hip arthroplasty (THA) under spinal anesthesia

Exclusion Criteria:

Pregnancy (confirmed by beta-HCG test if applicable) Known peripheral neuropathy or major neurological disease Chronic pain syndromes or long-term opioid use (>20 mg oral morphine equivalents/day) Severe hepatic or renal insufficiency Allergy to local anesthetics Major coagulopathies Vulnerable patients (e.g., minors, legally protected individuals)

Patient data will be anonymized and collected via the REDCap platform, compliant with current data protection regulations. Only the principal investigator and authorized study personnel will have access. Data will be stored securely for 10 years.

The patient, the surgeon, and the postoperative data collector will be blinded to the allocation. Only the anesthesiologist performing the block (who is not involved in patient follow-up or data collection) will know the specific technique and dosage used