Ultrasound Device Reliability for Measuring Patellar Tendon Cross-Sectional Area

This study evaluated the intra- and inter-rater reliability of a special device (SD) used for measuring the cross-sectional area (CSA) of the patellar tendon (PT) with ultrasound. Forty trained adult volunteers participated, and the ultrasound probe was placed at 25%, 50%, and 75% of the PT length with the knee positioned at 90°. Two raters and one analyzer obtained the images. A two-way ANOVA was conducted to assess the reliability, with no significant differences found between raters or conditions. Intra-rater reliability ranged from moderate to good, indicating consistent measurements from the same rater over time. Inter-rater reliability without the SD varied from low to good, but it improved when the SD was used, ranging from moderate to good. The use of the SD resulted in a lower coefficient of variation at the PT ends, suggesting improved measurement consistency at these locations. A moderate correlation was observed at the ends of the PT, and a strong correlation was found at the central region between the conditions with and without the SD. The mean difference in CSA measurements was small (approximately 0.013 cm² or 1.7%), indicating that the SD provided similar results to the standard method. However, the upper limit difference reached 43.2%, and the lower limit was 32.5%. Based on these findings, the study concluded that the SD is particularly useful for evaluating the ends of the PT, where measurement variability can be higher. For the central region, the SD is optional, as it does not significantly improve accuracy compared to standard ultrasound. Overall, the SD enhances the reliability of CSA measurements of the PT, particularly at the ends.