Erector Spinae Plane Block for Acute Low Back Pain

Inclusion Criteria: * Adult (≥ 18 years); * Non-specific low back pain (≤ 5 days); * Pain score (VAS) ≥ 5 (during mobilization); * Inability to walk easily (failure of the "Get Up and Go" test in less than 20 seconds). Exclusion Criteria: * Low back pain of known specific origin: spine surgery, spine trauma, discal hernia, facet joint, radicular (sciatica, cruralgia, meralgia paresthetica), muscle pain, cancer-related or rheumatological disease; * Referred or chronic pain; * Patients with opioids (acute or chronic pain and/or misuse); * Contraindication to regional anaesthesia; * Contraindication to ropivacaine, dexamethasone, sodium chloride, NSAID, paracetamol, tramadol; * Known hypersensitivity to ropivacaine, dexamethasone, other amide-type local anesthetics, or any of the excipients; * Addiction to drugs, alcohol or medication; * Patients with anticoagulants for a curative use (not preventive); * Patients with cancer or risk of bone metastasis or; severe osteoporosis; * Acute inflammatory diseases (e.g., rheumatoid arthritis, ankylosing spondylitis…); * Patient with severe hypotension or uncontrolled hypertension or; Heart Block (uncorrected second- or third-degree heart block without a pacemaker) or; severe bradycardia; * Patients with severe liver or renal disease or peptic ulcer disease; * Presence of infection or sepsis at the injection site; * Patients with uncontrolled bacterial, viral, or protozoan infections or; systemic fungal infections or; active untreated …