Full- versus partial-thickness Achilles tendon tears: Sonographic accuracy and characterization in 26 cases with surgical correlation

PURPOSE: To determine the accuracy of the use of sonography for differentiation of full- from partial-thickness tears or tendinosis of the Achilles tendon by using surgical findings as the standard of reference and to identify sonographic characteristics of full-thickness tears that can be used to differentiate the two types of tears. MATERIALS AND METHODS: In part A of this study, sonographic findings (based on reports) in 26 consecutive cases of tears of the Achilles tendon were compared with surgical findings. In part B, the sonograms were blindly and retrospectively evaluated with respect to six sonographic characteristics possibly related to pathologic findings in the tendon, and the characteristics were correlated with surgical findings. RESULTS: In part A, statistical data regarding the use of sonographic findings to distinguish full- from partial-thickness tears were as follows: sensitivity, 100%; specificity, 83%; accuracy, 92%; positive predictive value, 88%; and negative predictive value, 100%. In part B, tendon thickness (P < .001), posterior acoustic shadowing (P = .007), and tendon retraction (P < .001) were correlated with full-thickness tears. Visualization of fat herniation (P = .051) and of the plantaris tendon (P = .098) demonstrated marginal correlation with full-thickness tears. Echogenicity at the site of the pathologic finding in the tendon showed no significant correlation. CONCLUSION: Sonography can be used to differentiate full- from partial-thickness tears or tendinosis of the Achilles tendon with 92% accuracy. Undetectable tendon at the site of injury, tendon retraction, and posterior acoustic shadowing demonstrate statistically significant correlation with full-thickness tears.