Reliability of 3D freehand ultrasound to assess lower limb muscles in children with spastic cerebral palsy and typical development

• Published in: Journal of anatomy Vol. 242; no. 6; pp. 986 - 1002
• Main Authors: Hanssen, Britta, Peeters, Nicky, Dewit, Tijl, Huyghe, Ester, Dan, Bernard, Molenaers, Guy, Van Campenhout, Anja, Bar‐On, Lynn, Van den Broeck, Christine, Calders, Patrick, Desloovere, Kaat
• Format: Journal Article
• Language: English
• Published: England Wiley Subscription Services, Inc 01.06.2023; John Wiley and Sons Inc
• Subjects: 3D freehand ultrasound; Adolescent; Cerebral palsy; Cerebral Palsy - diagnostic imaging; Child; Children; echo‐intensity; Humans; Investigations; Lower Extremity - diagnostic imaging; muscle length; muscle morphology; muscle volume; Muscle, Skeletal - diagnostic imaging; Muscles; Original; Paralysis; pediatrics; reliability; Reproducibility of Results; Skeletal muscle; Tendons; Ultrasonic imaging; Ultrasonography - methods; Ultrasound; muscle morphology; 3D freehand ultrasound; echo-intensity; pediatrics; reliability; cerebral palsy; muscle volume; muscle length
• ISSN: 0021-8782; 1469-7580; 1469-7580
• DOI: 10.1111/joa.13839

This study investigated the reliability of 3‐dimensional freehand ultrasound (3DfUS) to quantify the size (muscle volume [MV] and anatomical cross‐sectional area [aCSA]), length (muscle length [ML], tendon length [TL], and muscle tendon unit length [MTUL]), and echo‐intensity (EI, whole muscle and 50% aCSA), of lower limb muscles in children with spastic cerebral palsy (SCP) and typical development (TD). In total, 13 children with SCP (median age 14.3 (7.3) years) and 13 TD children (median age 11.1 (1.7) years) participated. 3DfUS scans of rectus femoris, semitendinosus, medial gastrocnemius, and tibialis anterior were performed by two raters in two sessions. The intra‐ and inter‐rater and intra‐ and inter‐session reliability were defined with relative and absolute reliability measures, that is, intra‐class correlation coefficients (ICCs) and absolute and relative standard error of measurement (SEM and SEM%), respectively. Over all conditions, ICCs for muscle size measures ranged from 0.818 to 0.999 with SEM%s of 12.6%–1.6%. For EI measures, ICCs varied from 0.233 to 0.967 with SEM%s of 15.6%–1.7%. Length measure ICCs ranged from 0.642 to 0.999 with SEM%s of 16.0%–0.5%. In general, reliability did not differ between the TD and SCP cohort but the influence of different muscles, raters, and sessions was not constant for all 3DfUS parameters. Muscle length and muscle tendon unit length were the most reliable length parameters in all conditions. MV and aCSA showed comparable SEM%s over all muscles, where tibialis anterior MV was most reliable. EI had low‐relative reliability, but absolute reliability was better, with better reliability for the distal muscles in comparison to the proximal muscles. Combining these results with earlier studies describing muscle morphology assessed in children with SCP, 3DfUS seems sufficiently reliable to determine differences between cohorts and functional levels. The applicability on an individual level, for longitudinal follow‐up and after interventions is dependent on the investigated muscle and parameter. Moreover, the semitendinosus, the acquisition, and processing of multiple sweeps, and the definition of EI and TL require further investigation. In general, it is recommended, especially for longitudinal follow‐up studies, to keep the rater the same, while standardizing acquisition settings and positioning of the subject. Reliability was similar for typically developing children and children with spastic cerebral palsy, but the influence of different muscles, raters, and sessions was not constant for all parameters. Lengths were most reliable, followed by muscle volume and anatomical cross‐sectional. Echo intensity had low relative reliability with higher absolute reliability. 3DfUS seems applicable for differences between cohorts and functional levels. Applicability on an individual level is muscle‐ and parameter‐dependent.