Short Terms Effects of Medial Branch Block vs Para-spinal Muscle Injection in Patients With Non-specific CLBP

This study compares the efficacy of medial branch block (MBB) vs. paravertebral deep intramuscular (PDI) injection for pain relief in chronic low back pain. Based on randomization in first intervention session, one side receives MBB and the other side takes PDI and in second session the pattern reverses.

Inclusion Criteria: * CLBP of non-malignant origin fulfilling the following criteria: * Pain lasting for at least three months * Pain in both the left and right sides of the back * Pain below the L2 vertebral body * Lumbar spine CT scan or MRI done in the last 2 years * Average visual analogue scale (VAS) for pain ≥4/10 on each side for the 3 days * Cognitive and physical ability to provide informed consent in English or French Exclusion Criteria: * Neurologic signs or symptoms suggesting nerve root involvement * Strictly unilateral Low Back Pain (LBP) * CT scan or MRI findings suggestive of pain etiology beyond degenerative spine disease * Vascular malformations * Tumor * Infection * Fractures * DISH (Diffuse idiopathic skeletal hyperostosis) * Patients who have received injections of any type or acupuncture therapy to the low back in the last 3 months * Prior spine surgery * Local or systemic infection * Bleeding disorder or the use of anticoagulation medications but for low-dose aspirin * Known allergy to amid local anesthetics * Active insurance claim (CSST, SAAQ) * Uncontrolled psychiatric condition