Inter-rater reliability and measurement error of sonographic muscle architecture assessments.
OBJECTIVE
Sonography of muscle architecture provides physicians and researchers with information about muscle function and muscle-related disorders. Inter-rater reliability is a crucial parameter in daily clinical routines. The aim of this study was to assess the inter-rater reliability of sonographic muscle architecture assessments and quantification of errors that arise from inconsistent probe positioning and image interpretation.


METHODS
The medial gastrocnemius muscle of 15 healthy participants was measured with sagittal B-mode ultrasound scans. The muscle thickness, fascicle length, superior pennation angle, and inferior pennation angle were assessed. The participants were examined by 2 investigators. A custom-made foam cast was used for standardized positioning of the probe. To analyze inter-rater reliability, the examinations of both raters were compared. The impact of probe positioning was assessed by comparison of foam cast and freehand scans. Error arising from picture interpretation was assessed by comparing the investigators' analyses of foam cast scans independently. Reliability was expressed as the intraclass correlation coefficient (ICC), inter-rater variability (IRV), Bland-Altman analysis (bias ± limits of agreement [LoA]), and standard error of measurement (SEM).


RESULTS
Inter-rater reliability was good overall (ICC, 0.77-0.90; IRV, 9.0%-13.4%; bias ± LoA, 0.2 ± 0.2-1.7 ± 3.0). Superior and inferior pennation angles showed high systematic bias and LoA in all setups, ranging from 2.0° ± 2.2° to 3.4° ± 4.1°. The highest IRV was found for muscle thickness (13.4%). When the probe position was standardized, the SEM for muscle thickness decreased from 0.1 to 0.05 cm.


CONCLUSIONS
Sonographic examination of muscle architecture of the medial gastrocnemius has good to high reliability. In contrast to pennation angle measurements, length measurements can be improved by standardization of the probe position.
University Outpatient Clinic, Sports Medicine and Sports Orthopedics, University of Potsdam, Am Neuen Palais 10, Haus 12, 14469 Potsdam, Germany. mcassel@uni-potsdam.de.
Niklas
N
König
Michael
M
Cassel
Konstantina
K
Intziegianni
Frank
F
Mayer
D000328:Adult; D005260:Female; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000033:anatomy & histology* / Q000000981:diagnostic imaging*; D015588:Observer Variation; D009929:Organ Size; D011361:Professional Competence / Q000706:statistics & numerical data*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014463:Ultrasonography / Q000706:statistics & numerical data*
gastrocnemius muscle; inter-rater variability; muscle architecture; musculoskeletal ultrasound; sonography