This is a prospective; double blinded randomized controlled trial that will be conducted on cancer patients subjected to oncologic thigh surgery.The aim of this study is to evaluate and compare the analgesic effect of supra-inguinal fascia iliaca block and lumbar erector spinae plane block in oncologic thigh surgery.Patients will be randomized into three equal comparable groups, Group A (Ultrasound-guided supra-inguinal fascia iliaca block (SIFIB)), Group B (Ultrasound-guided lumbar erector spinae plane block (L-ESPB)), and Group C (control group). Primary outcome parameter is the total postoperative morphine consumption over the first 24 hours postoperative. Data will be analyzed using IBM SPSS 26 (SPSS Inc., Chicago, IL).

Pain is one of the most common and significant postoperative events experienced by many surgical patients. Orthopedic surgery is a relatively painful surgery due to the significant amount of bone and soft tissue resection, damage, and reconstruction. After thigh surgery for sarcomas, the patient may experience any of three distinct types of pain, including acute postoperative pain, persistent long-term nociceptive pain, and neuropathic pain related to intraoperative nerve injuries. The management of pain in limb sparing surgery patients and amputated patients is crucial during the rehabilitation program and often its approach is multidisciplinary. The ultrasound-guided supra-inguinal fascia iliaca block further built on earlier anatomic discoveries to more reliably anesthetize the three nerves: femoral, lateral femoral cutaneous, and obturator. The supra-inguinal fascia iliaca block has evolved as an effective means of providing analgesia to the thigh, the knee, and, most notably, the hip. Ultrasound-guided erector spinae plane block (ESPB) is an interfascial plane block reported in the treatment of postoperative pain from surgical procedures, ranging from shoulder to hip surgery. When performed at the lumbar 4th vertebral level, ESPB led to sensorial blockage between Th12 and L4 dermatomes lead to effective postoperative analgesia in hip and proximal femoral surgery. Although supra-inguinal fascia iliaca block and L-ESPB successfully reduced postoperative opioid consumption in previous study, no study has ever compared their efficacy in postoperative analgesia of adult patients undergoing oncologic thigh surgery under general anesthesia. Thus, in this randomized comparative study we are aiming to fill this gape in the literature.

Inclusion Criteria:

• Age: 18-65 years.
• Physical status: ASA II,III
• Patient undergoing oncologic thigh surgery under general anesthesia.
• Body mass index (BMI): 20-40 kg/m 2

Exclusion Criteria:

• Patient refusal.
• Sensitivity or contraindication to local anesthetics.
• Bleeding tendency due to coagulopathy.
• Patients with opioid dependence or alcohol or drug abuse.
• Patients with psychiatric illness that prevent them from proper perception and assessment of pain.
• Contraindication to regional anesthesia e.g. local infection at the site of block, coagulopathy with INR more than 1.6: hereditary (e.g. hemophilia, fibrinogen abnormalities & deficiency factor II) acquired (e.g. impaired liver functions with PC less than 60%, vitamin K deficiency & therapeutic anticoagulant drugs) .
• Significant renal insufficiency (plasma creatinine more than 1.5 mg/dl).