Do various baseline characteristics of transversus abdominis and lumbar multifidus predict clinical outcomes in nonspecific low back pain?

The evidence associated with the ability of baseline morphometry of transversus abdominis and lumbar multifidus to predict clinical outcomes of conservatively treated patients with nonspecific low back pain is not in agreement. Even though individual reports suggest that baseline morphometry or activity of transversus abdominis or lumbar multifidus predict clinical outcome of low back pain (LBP), a related systematic review is not available. For this reason, the review summarized evidence regarding the predictive value of these muscular characteristics. Candidate publications were identified from 6 electronic medical databases. After review, 5 cohort studies were included. While the review aimed to encompass studies using different muscle assessment methods, all included studies coincidentally used ultrasound imaging. No research investigated the relation between static morphometry and clinical outcomes. Evidence synthesis did not reveal much evidence supporting poor baseline transversus abdominis contraction thickness ratio as a treatment effect modifier favoring motor control exercise. Limited evidence supported that high baseline transversus abdominis lateral slide was associated with higher pain intensity after various exercise interventions at 1-year follow-up. However, there was limited evidence for the absence of relation between the contraction thickness ratio of transversus abdominis or anticipatory onset of lateral abdominal muscles at baseline and the short- or long-term LBP intensity after exercise interventions.

The study found conflicting evidence for a relation between baseline percent thickness change of lumbar multifidus during contraction and the clinical outcomes of patients after various conservative treatments. Due to study heterogeneity, the small number of included studies and the inability of conventional greyscale B-mode ultrasound imaging to measure muscle activity, the authors’ findings should be interpreted with caution. Further large-scale prospective studies that use appropriate technology (ie, electromyography to assess muscle activity) ought to be conducted to investigate the predictive value of morphometry or activity of these muscles with respect to LBP-related outcomes measures.