Main indications for total hip arthroplasty (THA) are degenerative osteoarthritis of the coxofemoral joint, osteonecrosis of the hip, congenital disorders such as dysplasia and inflammatory arthritis. More recently, surgery using the direct anterior approach is getting popularity: this method, in fact, granting a significant sparing of the hip muscles, is associated with favorable results compared to other techniques, such as a lower risk of dislocation, limitated damage to soft tissues with better recovery and early discharge.

Patients undergoing this procedure may although experience moderate to severe postoperative pain in the first few hours (with peaks observed in the first 12 hours), as well as potential complications such as nausea and vomiting related to opioids use.

It has been shown that adequate pain control influences early mobilization and rehabilitation, ensuring a quicker recovery. The role of regional anesthesia techniques has been established in almost all areas of orthopedic surgery, and in particularly in the management of postoperative pain following hip replacement surgery, but definitive data are missing with regard to direct anterior approach.

Regional anesthesia consists of infiltrating local anesthetics in sites (fascial planes or nerves), in order to limit or even eliminate the use of traditional painkillers, with a significant reduction in the side effects.

The aim of this study is to compare the impact of two techniques, the Suprainguinal Fascia Iliaca (SIFI) block and the lumbar Erector Spinae Plane (ESP) block, in managing postoperative pain in subjects undergoing total hip replacement surgery performed by direct anterior approach.

The primary objective of the study is the incidence of residual femoral and obturator nerves block (knee extension and hip adduction according to ASIA score) 8 hours after surgery in the two treatment groups.

Secondary objectives include: • Time elapsed between the end of surgery and the recovery of lower limb motility enough to allow the patient to mobilize independently; • Total opioid consumption (calculated as morphine equivalents) at 8, 24 and 48 hours after surgery; • Pain according to NRS (numerica rating scale) at 8, 24 and 48 hours after surgery; • Extent of sensory block of the three branches of the lumbar plexus (femoral, obturator, lateral femorocutaneuous nerves) at 8, 24 and 48 hours after surgery; • Timing of hospital discharge; • Incidence of chronic or persistent postoperative pain (at 30 and 90 days after surgery); • Any postoperative complication

Inclusion Criteria:

• Age >=18 years and =<85 years
• patients undergoing elective unilateral THA with direct anterior approach
• patients able to understand the purposes of the study and provide signed informed consent

Exclusion Criteria:

• pregnancy
• Age <18 years or >85 years
• revision or bilateral surgeries
• psychiatric pathology or cognitive deficits, mental retardation, inability to provide valid informed consent
• History of illicit drugs and/or alcohol abuse
• urgent/emergent surgery with admission to Intensive Care under sedation and mechanical ventilation or complications that do not allow evaluation
• known allergy to the drugs used in the study
• refusal to provide informed consent