Clinical Validity of Shear Wave Elastography for Post-Stroke Spasticity: A Systematic Review and Meta-Analysis

Background/Objectives: Shear wave elastography (SWE) has emerged as a quantitative imaging technique for assessing muscle mechanical properties and has been increasingly applied to post-stroke spasticity. However, the clinical validity of SWE relative to established clinical spasticity scales and the influence of assessment protocols remain incompletely understood. This systematic review and meta-analysis aimed to evaluate the clinical validity of SWE for post-stroke spasticity and to identify clinically relevant methodological moderators. Methods: A systematic literature search was conducted in PubMed, Cochrane Library, CINAHL, and Web of Science to identify studies reporting correlations between SWE measures and clinical spasticity scales in individuals with stroke. Random-effects meta-analyses were performed using robust variance estimation to account for dependent effect sizes within studies. Prespecified subgroup and meta-regression analyses examined potential moderators, including clinical scale, muscle position during assessment, output metric, limb segment, and stroke chronicity. Results: Ten studies involving 303 participants contributed 38 correlation estimates. The pooled correlation between SWE and clinical spasticity scales was moderate (r = 0.42, 95% CI 0.34-0.49). SWE demonstrated significantly stronger correlations with the Modified Tardieu Scale than with the Modified Ashworth Scale. Measurements obtained in stretched muscle positions showed higher validity than those obtained at rest. Other examined moderators were not statistically significant. No evidence of publication bias was detected. Conclusions: SWE shows a moderate association with clinician-rated spasticity scales and appears to reflect the mechanical consequences of post-stroke spasticity. Associations were influenced by scale selection and measurement position. These findings support protocol-informed integration of SWE as a quantitative adjunct for assessing passive muscle stiffness rather than as a replacement for established clinical scales.