Reliability and validity of assessing lower-limb muscle architecture of patients with cerebral palsy (CP) using ultrasound: A systematic review

Aims: To investigate the reliability, validity, and level of evidence of applying ultrasound in assessing the lower-limb muscles of patients with cerebral palsy (CP). Method: Publications in Medline, PubMed, Web of Science, and Embase were searched on May 10, 2023, to identify and examine relevant studies investigating the reliability/validity of ultrasound in evaluating the architecture of CP lower-limb muscles systematically, following the Preferred Reporting Items for Systematic Reviews and Meta-Analysis 2020 guidelines. Results: Out of 897 records, 9 publications with 111 CP participants aged 3.8–17.0 years were included (8 focused on intra-rater and inter-rater reliability, 2 focused on validity, and 4 were with high quality). The ultrasound-based measurements of muscle thickness (intra-rater only), muscle length, cross-sectional area, muscle volume, fascicle length, and pennation angle showed high reliability, with the majority of intraclass correlation coefficient (ICC) values being larger than 0.9. Moderate-to-good correlations between ultrasound and magnetic resonance imaging measurements existed in muscle thickness and cross-sectional area (0.62 ≤ ICC ≤ 0.82). Interpretation: Generally, ultrasound has high reliability and validity in evaluating the CP muscle architecture, but this is mainly supported by moderate and limited levels of evidence. More high-quality future studies are needed.