Regional anesthesia is commonly used in orthopedic and surgical procedures in ankle and foot surgery to manage pain. The ultrasound-guided nerve block is a safe and effective regional anesthesia technique that provides effective pain management, decreasing opioid consumption.

Postoperative pain management may be challenging and requires a multimodal approach. Regional anesthesia techniques in the pediatric ankle and foot surgery population are frequently used in postoperative pain management due to ultrasonography's increased experience and accessibility.

Erector spinae plane block (ESP) is a relatively new regional anesthesia technique that provides analgesia covering spinal nerves' dorsal and ventral rami. There are few cases reports in the literature on the use of ESP block for lower limb surgery, for which it has a promising potential for future indication.

The erector spinae plane block is a safe and effective regional anesthesia technique, which has earned new indications perioperatively since its description.

This single-center study was a prospective randomized controlled trial, using parallel groups with a 1:1 allocation ratio. Eligible patients were identified by the surgeon and invited to participate in the study. If the patient wished to participate in the study, informed consent was obtained. The patient was informed of the study's nature, especially that the patient would be randomized to receive an ESPB or a sham block before the procedure. A computerized randomization program (permuted block randomization) was used to create the allocation before the beginning of the study. Research staff not involved in the recruitment process or the study's conduct randomized patients at the time of admission to the clinic. Randomization allocation was 1:1 between treatment and control groups. Apart from the anesthesiologists who performed the blocks, all patients, surgeons, and postoperative nurses remained blinded to randomization throughout the study period. The outcome parameters were recorded through a study nurse who was not involved in the patients' care.

All patients received standardized anesthesia, and all blocks were performed by 2 anesthesiologists who were trained in this technique. A large-bore intravenous (IV) line was placed, and patients received midazolam 1 to 2 mg IV for anxiolysis.

Anesthesia was induced with fentanyl 2 mcg.kg-1 and propofol 2 mg.kg-1 followed by atracurium 0.5 mg.kg-1 . After intubation, anesthesia was maintained with isoflurane (1 MAC) and atracurium 0.1mg.kg-1 as a maintenance dose every 30 min until the end of the procedure. After emerging from anesthesia, patients were transferred to the postanesthesia care unit (PACU) for a 2-h observation period. Patients were discharged from the PACU when they achieved a modified Aldrete score ≥ 9.10. Postoperative analgesia was provided in both groups immediately after surgery by PCA fentanyl pump, then oral acetaminophen 1 g four times a day. The criteria to stop the fentanyl titration protocol included satisfactory pain control, increased sedation (Ramsay sedation scale >2), decreased respiratory rate.

Statistical Analyses The sample size was estimated to achieve a power of 0.8 to detect a supposed medium effect size of 0.7 in between the two groups regarding total morphine consumption, with a 2-sided significance level of .05 and allocation ratio of 1. Thirty patients in each group were required. Allowing for a 10% loss, 34 patients were recruited in each group, for a total of 68 patients. The sample size was determined using G*Power software (version 3.1.9.7).

Descriptive statistics, including age, sex, body mass index, baseline pain scores, procedure type, traction time, and procedure time, were comparatively analyzed between the groups. Categorical data were compared with chi-squared and Fisher's exact tests as appropriate. Continuous data were compared with a 2-sided t test (for normally distributed data) and Wilcoxon rank-sum test (for non normally distributed data). For all analyses (primary and secondary measures), a P value of .05 was used to determine statistical significance. Statistical analyses were conducted using SPSS version 28 (Addinsoft, Paris, France).

Inclusion Criteria:

• Age 18 - 65 years, American Society of Anesthesiologists physical status classification Ι and ΙΙ; scheduled for ankle and foot surgery

Exclusion Criteria:

• Major hepatic
• severe renal impairment (creatinine > 3 or on dialysis);
• severe cardiovascular disease (ejection fraction < 35%)
• local infection at site of injection
• Any contraindication for ESP
• Known allergy to any drug used in the study

Apart from the anesthesiologists who performed the blocks, all patients, surgeons, and postoperative nurses remained blinded to randomization throughout the study period.