Application of Ultrasound Shear Wave Elastography as an Objective Outcome Measure in Nonspecific Low Back Pain Associated with Myofascial Trigger Points.

OBJECTIVES

To assess the reliability, clinical association, and discrimination of an ultrasound shear wave elastography (SWE) protocol in individuals with nonspecific low back pain (NSLBP) associated with myofascial trigger points.

DESIGN

Cross-sectional observational study.

SETTING

A university laboratory.

PARTICIPANTS

Fifteen individuals (N=15) with NSLBP had a mean age of 37.60±6.50 years, with a sex distribution of 4 men and 11 women and a symptom duration of >3 months. An additional 15 asymptomatic controls (ACs) (mean age 36.73±6.65y) were individually matched to the NSLBP group based on age (±5y), sex, physical activity level, and side of image acquisition.

INTERVENTIONS: Not applicable.

MAIN OUTCOME MEASURES: The primary outcome was muscle stiffness, assessed using SWE and quantified by shear wave speed. Secondary outcomes included pain intensity and disability, assessed using the Visual Analog Scale and the Oswestry Disability Index, respectively.

RESULTS

Both physiotherapist and radiologist demonstrated good-to-excellent reliability for SWE and shear wave speed measurements. Quadratus lumborum (QL) stiffness was strongly and negatively correlated with pain intensity (r=-0.64, P=.03) and age (r=-0.64, P=.02). Psoas major (PM) stiffness was also negatively correlated with age (r=-0.58, P<.05). The protocol discriminated QL stiffness between individuals with NSLBP and AC, with a median between-group difference of 5.98 kPa (95% CI, 0.42-7.30 kPa; P=.02).

CONCLUSIONS

A well-trained physiotherapist appears to be able to quantify deep lumbar muscle stiffness. QL and PM stiffness values were preliminarily associated with clinical characteristics and showed potential to discriminate between individuals with NSLBP and ACs. Further validation with larger samples and multiple raters is required to support its potential as an objective outcome measure for clinical assessment and treatment monitoring in NSLBP.