Total hip arthroplasty (THA) is one of the main elective orthopedic surgery. Recent studies have proven that patients undergoing an elective THA who are part of a fast track surgery program including an opioid free anesthesia (OFA) presented a decrease of mortality and a reduced in-hospital length of stay. Based on the anatomical knowledges, the Quadratus Lumborum Block seems to be an interesting locoregional technique for patients undergoing THA. So far, there is no recommanded locoregional aesthesia in this indication. The investigators hypothezised that QLB would give an efficient analgesia in the 24h following a THA.

Therefor, the study performed a prospective, randomized, double blind trial in the Nice Universitary hospital of Pasteur 2 and in Arnault Tzanck Institute among all patients who underwent THA, comparing a QLB using ropivacaïne 2mg/ml 20ml vs isotonic saline solution 20 ml.The main end-point is the decrease opiod consumption in the 24h following THA.

Inclusion Criteria:

• All adult patients with unilateral programmed total hip prosthesis surgery are included in the absence of inclusion criteria.

• Obligation for all patients to be affiliated with social security
• Patient Informed Consent Signature

Exclusion Criteria:

• chronic opiod consumption

• pregnancy

• mental disorder that prevents the usage of the numeric analog scale

• Contra indications of the realization of QLB

  • Local infection
  • Allergic to the local anesthesia
  • Hemostasis disorder
  • Incapacity of giving the consent : individuals under guardianship by court order, or under judicial protection