Elastic Characteristics of the Normal Achilles Tendon Assessed by Virtual Touch Imaging Quantification Shear Wave Elastography

Abstract

he Achilles tendon is the largest, thickest, and strongest tendon in the human body. Problems with the Achilles tendon are frequent in athletes and the general population because of the increased incidence of sports-related injuries, which cause foot and ankle pain. [1][2][3][4] The area 5 cm proximal to the calcaneus is especially predisposed to tendinopathy and subsequent tearing due to vascular and biomechanical factors. Sonography plays an important role in the evaluation of tendon disorders, owing to its low cost, relative availability, noninvasiveness, and dynamic character. However, its diagnostic accuracy remains controversial. 5,6 Magnetic resonance imaging is a useful modality for imaging the Achilles tendon, but it is expensive and time-consuming.Shuai Fu, MD, Ligang Cui, MD, Xiaoxi He, MD, Yang Sun, MD Received January 20, 2016, Methods-A total of 326 healthy volunteers older than 18 years were divided into different groups by sex and age. The thickness, shear wave velocity (SWV) in sagittal and axial sections, and anisotropic coefficient of the Achilles tendon in a state of relaxation were obtained by conventional sonography and Virtual Touch imaging quantification elastography. These parameters were compared in different age and sex groups, and their correlations with age were evaluated.Results-The thickness of the Achilles tendon in men and women increased gradually with age, and it was larger in men than in women in each age group (P < .05). The SWV of the tendon in the sagittal section decreased slightly with age, but the sagittal and axial SWVs and anisotropic coefficient had no significant differences among different age groups (P > .05), and they also had no significant differences between men and women within any group (P > .05). The SWVs in the sagittal and axial sections and anisotropic coefficient had no correlation with age. Intraclass correlation coefficients for sagittal and axial SWVs obtained by 2 independent observers were 0.923 and 0.870, respectively.Conclusions-The thickness of the Achilles tendon increased gradually with age. We confirmed that tendinous elastographic anisotropy and the stiffness of the tendon had no significant correlation with age.

Current status of musculoskeletal application of shear wave elastography

“…As a result, guided wave propagation may lead to a false evaluation of the Young modulus, which is the reason that shear wave velocities are usually preferred to Young moduli in tendon imaging [6,22,32]. In addition, the high shear wave velocity of hard tendon can exceed the upper limit of measurement of shear wave velocity of the device (maximum scale value) [32,33]. In the Acuson S3000 ultrasound system Virtual Touch imaging quantification (VTIQ; Siemens Medical Solutions, Malvern, PA, USA), the maximum scale value is 10 m/sec [33], and in the Imagine Aixplorer system (Supersonic Imagine, Aix-en-Provence, France), it is 16.3 m/sec [34].…”

“…Due to the high anisotropy, tendon imaging requires the US beam position to be perfectly parallel or perpendicular to the tendon fibers; however, the tendons may have a complex structure due to interpenetration and rotation of fibers from muscles, and sometimes proper positioning of the US beam cannot be achieved [32,33]. Several studies of the Achilles tendon have reported large differences in elasticity values in the transverse (axial) and longitudinal (sagittal) orientations of the probe and the neutral position, extension, and dorsiflexion of the ankle [32,33,35,36].…”

“…Several studies of the Achilles tendon have reported large differences in elasticity values in the transverse (axial) and longitudinal (sagittal) orientations of the probe and the neutral position, extension, and dorsiflexion of the ankle [32,33,35,36]. …”

Real-time sonoelastography: principles and clinical applications in tendon disorders.

“…Subsequently, Arda et al 13 reported on elasticity values of Achilles tendons using a numeric scale in healthy volunteers, with a mean of 51.5 ± 25.1 kPa as Young modulus. During aging, Achilles tendon exhibited an increased stiffness when compared to young adults 14,15 ; however, other Authors did not find any correlation 16 . A positive correlation was found between tendon stiffness and BMI 17 ; results in smokers are controversial 17,18 .…”

“…SE was also able to detect tissue changes in symptomatic patients with normal US 31 , and to screen athletes at risk of developing symptoms during the season 21 . For these reasons, SE is considered a valuable tool to valuate "in vivo" and in a non-invasive way the biomechanical properties of various tendons 16 bypassing artefacts of surgical repair, such as tendons sutures 38 .…”