This study concerns the treatment of recent lumbago and aims to evaluate the efficacy of an anesthetic block of the erector spinae muscles combining ropivacaine and dexamethasone. This treatment is routinely used in several institutions in France, but has never been the subject of a randomized placebo-controlled study to assess its efficacy at D4 of treatment.

The BLOCLOMB comparative, randomized, double-blind study aims to validate the efficacy, over the first 4 days, of anesthetic blocks of the erector spinae muscles, during recent lumbago, on the pain of muscular contractures.

Inclusion Criteria:

1. Patient with lumbago lasting less than 7 days despite analgesic / NSAID treatment.
2. Patient with NS pain > 6
3. Patient with Oswestry score > or equal to 30
4. Patient informed of the trial and having signed the informed consent form prior to any trial-specific procedure,
5. Patient willing and able to undergo all planned examinations and procedures in compliance with the clinical trial protocol,
6. Patient affiliated to a social security or any health insurance.

Exclusion Criteria:

1. Presence of "red flag" (non-disc lumbago):

   • Motor deficit or signs of horsetail irritation
   • Inflammatory pain waking up in the 2nd half of the night
   • Tumoral context
   • Infectious context or fever
   • Altered general condition
   • Traumatic context
   • Osteoporotic context

2. Risk of infection

3. Patient with poor local skin condition

4. Patient on AVK or anti-Xa anticoagulation, or bleeding disorder (antiaggregants authorized)

5. Patients with hypersensitivity to Ropivacaine or any of its excipients: Sodium chloride, hydrochloric acid sodium hydroxide

6. Patient with sciatica

7. Patient with chronic respiratory insufficiency

8. Patient with cardiac rhythm disorders

9. Pregnant or breastfeeding woman or woman refusing effective contraception

10. Patient deprived of liberty or under legal protection (guardianship or curator)

11. Patient participating in another clinical research protocol involving a drug or medical device

12. Patient unable to follow the protocol, as judged by the investigator

13. Patient refusing to participate in the study