Introduction: Modic changes have recently been identified as a pain giving pathoanatomical diagnosis for a considerable percentage (20–30 %) of Low Back Pain (LBP) patients. The causes of these Modic changes have not been determined conclusively.

The aim was to evaluate a possible effect of antibiotic treatment in an uncontrolled group of patients with LBP and Modic changes.

Methods: A cohort of patients (n=32) participated in this study. The patients had previous sciatic mostly from lumbar disc herniation, all were treated conservatively. At the 14 month follow-up, 43 of the patients had Modic changes, six of whom did not suffer from LBP, five declined participation. The treatment consisted of amoxicillin-clavulanate (500 mg/125 mg) (Spektramox ®) three times a day for 90 days.

Results: Twenty-nine patients completed the treatment, of which 15 (52 %) reported that they were much better or cured, 7 (24 %) experienced moderate improvement, and 7 (24 %) remained unchanged. None reported a worsening of symptoms. At the end of treatment and at long term follow-up (mean 10.8 months) there was both a clinically and statistically significant (p< 0.001) improvement found in all outcome parameters, namely; general health, disease and patient specific function, pain in the lumbar area, and number of days with pain.

Discussion: The clinical effect of antibiotic treatment was profound in a group of patients suffering from persistent low back pain after experiencing a disc herniation. Our results support the theory that bacterial infection could play a role in LBP with Modic changes.