Reliability and validity of a dual-probe personal computer-based muscle viewer for measuring the pennation angle of the medial gastrocnemius muscle in patients who have had a stroke.

Background A dual-probe personal computer-based muscle viewer (DPC-BMW) is advantageous in that it is relatively lightweight and easy to apply. Objective To investigate the reliability and validity of the DPC-BMW in comparison with those of a portable ultrasonography (P-US) device for measuring the pennation angle of the medial gastrocnemius (MG) muscle at rest and during contraction. Methods Twenty-four patients who had a stroke (18 men and 6 women) participated in this study. Using the DPC-BMW and P-US device, the pennation angle of the MG muscle on the affected side was randomly measured. Two examiners randomly obtained the images of all the participants in two separate test sessions, 7 days apart. Intraclass correlation coefficient (ICC), confidence interval, standard error of measurement, Bland-Altman plot, and Pearson correlation coefficient were used to estimate their reliability and validity. Results The ICC for the intrarater reliability of the MG muscle pennation angle measured using the DPC-BMW was > 0.916, indicating excellent reliability, and that for the interrater reliability ranged from 0.964 to 0.994. The P-US device also exhibited good reliability. A high correlation was found between the measurements of MG muscle pennation angle obtained using the DPC-BMW and that obtained using the P-US device (p < 0.01). Conclusion The DPC-BMW can provide clear images for accurate measurements, including measurements using dual probes. It has the advantage of rehabilitative US imaging for individuals who have had a stroke. More research studies are needed to evaluate the usefulness of the DPC-BMW in rehabilitation.