Interobserver variability and stiffness measurements of normal common extensor tendon in healthy volunteers using shear wave elastography.

OBJECTIVES: The purposes of our study are to determine the quantitative elasticity values of normal common extensor tendon (CET) and to assess the interobserver variability of stiffness measurements using shear wave elastography (SWE).

MATERIALS AND METHODS: A total of 60 CETs of 30 (15 female, 15 male, mean age 30.2 years) healthy volunteers without any symptoms of lateral epicondylitis were examined by two radiologists. Age, sex, height, weight, body mass index (BMI), and dominant hand of all participants were noted. The first observer performed B-mode and SWE imaging, and the second observer performed only SWE imaging. Tendon thickness and stiffness values in kPa were measured.

RESULTS: The mean thickness of CETs was 3.57 ± 0.36 mm. The mean stiffness values of CETs for two observers were 45.28 ± 9.82 kPa and 45.80 ± 9.72 kPa respectively. Tendon thickness had a weak correlation with weight (r = 0.281, p = 0.03), and moderate correlation with stiffness values (r = 0.429, p < 0.001). The mean interobserver difference of CET stiffness measurements was -0.5% of the mean CET stiffness values. Range of measurement error, defined as 95% limits of agreement, was ±23.5%. There was no significant difference between absolute values of interobserver measurements (p = 0.741).

CONCLUSION: Shear wave elastography is a reproducible imaging technique for the evaluation of CET elasticity and the standard stiffness values of normal CET can be used as reference data to differentiate normal from pathological tissues.