Diaphragm Thickness and Excursion in Nonspecific Low Back Pain: A Critically Appraised Topic

Low back pain is a common musculoskeletal condition, with nonspecific low back pain (NS-LBP) accounting for the majority of cases. NS-LBP lacks a definitive pathological cause, complicating diagnosis and management. Emerging research has identified diaphragm dysfunction, including alterations in thickness and excursion, as a potential factor contributing to NS-LBP. Ultrasound is a noninvasive tool used to measure these diaphragm characteristics and explore their association with NS-LBP.

In patients with NS-LBP, is there a difference in diaphragm thickness and excursion (as measured by ultrasound) compared with healthy controls?

A systematic search yielded 4 high-quality case-control studies assessing diaphragm function in patients with NS-LBP. All 4 studies demonstrated significantly reduced diaphragm thickness in patients with NS-LBP compared with healthy controls. Findings on diaphragm excursion were inconsistent, with 1 study reporting significant differences while 3 showed no differences between groups. Reduced diaphragm thickness and slower changes in thickness were consistently associated with impaired spinal stabilization.

The evidence indicates a consistent difference in diaphragm thickness between individuals with NS-LBP and healthy controls, suggesting a potential role of diaphragm dysfunction in the pathophysiology of NS-LBP. However, inconsistent findings on diaphragm excursion warrant further investigation.

Based on the Strength of Recommendation Taxonomy, the clinical bottom line is based on grade A evidence for diaphragm thickness while diaphragm excursion is grade B.