Biomechanical Evaluation of Refractory Chronic Low Back Pain Treatment with Botulinum Toxin Type A

Abstract Objectives: To investigate changes in isometric strength and the cross-sectional area [CSA] of the lumbar extensors induced by botulinum toxin type A [BoNT-A] treatment and the relationship between these changes and the clinical efficacy of BoNT-A for reducing refractory chronic low back pain [LBP]. Methods: Thirty-five patients suffered from chronic LBP refractory to other conservative treatments. Each was injected with 50 units of BoNT-A [Dysport®, Llandudno, UK] at the tender points in the lumbar extensor muscles. Visual analog scale [VAS] pain scores, Oswestry Low Back Pain Questionnaire [OLBPQ] responses, changes in the isometric strength, and CSA of the lumbar extensors were assessed at baseline and 1, 2, and 3 months. Results: The VAS pain scores were significantly reduced at all post-treatment time points. A significant improvement in mean OLBPQ scores was evident at 2 and 3 months after treatment. Significant increases in lumbar extensor isometric strength were observed at three months on 0°, 24°, and 60° lumbar flexion angles. Increases in muscle size were seen at the L3-4 inter-vertebral level and the L4-5 inter-vertebral level at 3 months. No strong correlation was found between VAS score and isometric strength of the total lumbar extensor. The change in VAS scores was significantly correlated with the CSA of the L4-5 intervertebral level of extensor. A negative correlation was found between OLBPQ scores and isometric strength of the lumbar extensors. No serious adverse events were reported. Conclusion: The BoNT-A may have clinical utility in terms of pain reduction and functional improvement in patients with refractory chronic LBP. This therapy could serve as a suitable alternative for patients with refractory chronic LBP who experience no benefit from conservative treatments.