Can patient characteristics explain variance in ultrasound strain elastography measures of the quadratus femoris and patellar tendons?

Objectives: To explore the associations between participant characteristics and magnitudes of difference in paired elastography measures of knee tendon from different ultrasound systems, and to compare strain elastography pattern description.
Materials and Methods: Quadriceps and patellar tendons of 20 healthy volunteers (40 tendons) were examined by an experienced operator employing two ultrasound systems (GE S8 and Esaote MyLab 70XVG). Pearson/Spearman correlations explored the influence of participant characteristics (BMI, body fat %, leg circumference, activity level) on the magnitude of differences between measures. Paired-sample t test or Wilcoxon signed rank test were performed to compare repeated measures of individual ultrasound systems.
Results: The quadriceps tendon was characteristically stiffer than the patellar tendon. Participant characteristics were associated with within machine differences of the distal quadriceps tendon (BMI; r = 0.49, p = 0.028–0.03 and body fat %; r = 0.43, p = 0.05–0.056) ER measures.
Conclusions: Anthropometric and body composition parameters were associated with within machine differences for elasticity measures, where high BMI and body fat % contribute to paired measurement variance at the distal quadriceps tendon. Strain elastography protocols should be standardised, repeated ER measures performed using the same US system and patient characteristics considered for future clinical applications.