The interrater reliability of ultrasonography for Achilles tendon structure

AIM OF THE STUDY: Reliable assessment of Achilles tendon structure (architecture and morphology) may help prevent clinical symptoms or progression of Achilles tendinopathy. The objective of this study was to determine the interrater reliability of musculoskeletal ultrasonography for the assessment of the mid-portion of the Achilles tendon: (1) structure, (2) anteroposterior diameter and (3) neovascularization, in asymptomatic military personnel. MATERIAL AND METHODS: Two sonographers acquired B-mode images of the Achilles tendon mid-portion in 74 volunteers (148 tendons) in short-axis and long-axis planes to assess its structure and measure the maximum anteroposterior diameter. Power Doppler ultrasound was performed to assess neovascularization. Tendon structure and neovascularization were graded using a modified four-graded Öhberg score. RESULTS: Weighted kappa for assessing tendon structure showed almost perfect agreement (0.87; 95% CI: 0.79, 0.95). Spearman’s rho showed: a very high positive interobserver correlation for tendon structure (0.92; 95% CI: 0.89, 0.94), a very high positive interobserver correlation for the diameter measurement in the short-axis plane (0.91; 95% CI: 0.87, 0.93) and a high positive interobserver correlation in the long-axis plane (0.87; 95% CI: 0.83, 0.91). The Wilcoxon signed-rank test showed no significant differences between observers during diameter measurements (p value >0.05). Both sonographers reported absent neovascularization in all the subjects, resulting in overall Öhberg score of 0. CONCLUSIONS: (1) Interrater reliability of ultrasonography for grading the mid-portion Achilles tendon structure shows almost perfect agreement, and (2) ultrasonography is highly reliable in measuring the anteroposterior diameter. (3) In a large group of asymptomatic service members neovascularization of the Achilles tendon is consistently absent.