Intra and Inter-rater Reliability between Ultrasound Imaging and Caliper Measures to determine Spring Ligament Dimensions in Cadavers

The purpose was to evaluate intra and inter-rater reliability, repeatability and absolute accuracy between ultrasound imaging (US) and caliper measures to determine Spring ligament (SL) dimensions in cadavers. SLs were identified from 62 human feet from formaldehyde-embalmed cadavers. Intra and inter-observer reliability, repeatability and absolute accuracy of SL width, thickness and length between US and caliper measurements were determined at intra and inter-session by intraclass correlation coefficients, Pearson´s correlation coefficients, Student t tests, standard errors of measurement, minimum detectable changes, values of normality, 95% limits of agreement, and Bland-Altman plots. Excellent inter-session and inter-rater reliability, adequate absolute accuracy, almost perfect agreement and strong correlations were shown for caliper, US and their comparison for all SL dimensions. US measurements presented higher absolute accuracy than caliper measures for SL length and thickness dimensions, while caliper displayed greater absolute accuracy for SL width dimensions. Good repeatability (P > 0.05) was shown for all SL dimensions by US, caliper and their comparison, except for SL width dimension measured with US (P = 0.019). Both US and caliper could be recommended for all SL dimensions evaluation due to their excellent reliability and absolute accuracy in cadavers, although width dimensions should be considered with caution due to US repeatability differences.