Providing postoperative analgesia after hip joint surgery is essential in ensuring patient recovery and rehabilitation. The blocks that can be used as alternatives in these surgeries have diversified in recent years, and their superiority over each other is being investigated. The aim is to reach a method that provides more effective analgesia, is more practical and does not cause muscle weakness. For this reason, PENG, which has no previous comparative randomized studies, and iliopsoas blocks, which have more recent clinical studies, need to be examined.

All patients received standard general anaesthesia under standard monitoring along with the bispectral index (Medtronic) and nociception level index (NOL, MedaSense). Intubation was performed by administering intravenous (IV) 0,03 mg/kg midazolam 2 mg/kg, propofol (Lipuro, Braun), 2 mcg/kg fentanyl (Talinat, VEM), 0,6 mg /kg rocuronium (Esmeron, Alessandroorsini) followed by 1 MAC sevoflurane (Sevorane, Abbott) in an air-oxygen mixture for maintenance of anaesthesia. All participants received 20 mg tenoxicam and 1 gr paracetamol along with 8 mg dexamethasone before surgical incision as part of multimodal analgesia. All blocks were performed before surgical incision following the induction of general anaesthesia by a single experienced regional anaesthesiologist (B.C.) under ultrasound guidance (Esaote MyLab ™ Seven). Both groups received lateral femoral cutaneous nerve (LFCN) block by using a high-frequency probe to visualize LFCN between sartorius and tensor of fascia lata in line with the inguinal ligament, and 10 ml 0,375 bupivacaine was injected. After applying PENG or IP block in accordance with randomization, the surgery was set to begin after at least 15 minutes of block procedures. The intraoperative analgesic need was supplied by remifentanil infusion (2 mcg/mL) and determined by NOL index level, and a value over 25 for more than one minute was accepted as pain to be treated by increased remifentanil infusion doses. All patients received 8 mg of ondansetron and suggamadex (2 mg/kg) for decurarization before arousal under BIS guidance. From the beginning of acclaimed arousal till the 24th hour, rescue analgesia as tramadol 100 mg (maximum daily dose 400 mg) is applied if NOL is over 25 at the recovery room or NRS over 4 or with the patient's request. The routine analgesia regimen was 1 gram iv paracetamol 6th hourly postoperatively at the orthopaedic ward.

PENG block procedure Immediately after the insurance of general anaesthesia and LFCN block application, PENG block was performed by the primary investigator (B.C) following proper skin disinfection with the patient in the supine position. Under the guidance of a low-frequency curvilinear ultrasound probe, the iliopubic eminence and the psoas tendon were identified, and local anaesthetic (20 ml 0,375% bupivacaine) was injected between the periosteum and psoas tendon following negative aspiration.

IPB procedure After ensuring aseptic conditions, the low-frequency curvilinear ultrasound probe was transversely placed caudad to the anterior superior iliac spine, then rotated anticlockwise and slid along the inguinal ligament to detect the head of the femur, as described by Nielsen et al. The primary investigator (B.C.) directed the needle tip into the iliopsoas plane between the iliopsoas muscle and iliofemoral ligament through an in-plane approach, and 10 ml of 0,375% bupivacaine was injected.