Spatial variations in Achilles tendon shear wave speed

Abstract

Supersonic shear imaging (SSI) is an ultrasound imaging modality that can provide insight into tissue mechanics by measuring shear wave propagation speed, a property that depends on tissue elasticity. SSI has previously been used to characterize the increase in Achilles tendon shear wave speed that occurs with loading, an effect attributable to the strain-stiffening behavior of the tissue. However, little is known about how shear wave speed varies spatially, which is important, given the anatomical variation that occurs between the calcaneus insertion and the gastrocnemius musculotendon junction. The purpose of this study was to investigate spatial variations in shear wave speed along medial and lateral paths of the Achilles tendon for three different ankle postures: resting ankle angle (R, i.e. neutral), plantarflexed (P; R − 15 deg), and dorsiflexed (D; R + 15 deg). We observed significant spatial and posture variations in tendon shear wave speed in ten healthy young adults. Shear wave speeds in the Achilles free tendon averaged 12 ± 1.2 m/s in a resting position, but decreased to 7.2 ± 1.8 m/s with passive plantarflexion. Distal tendon shear wave speeds often reached the maximum tracking limit (16.3 m/s) of the system when the ankle was in the passively dorsiflexed posture (+15 deg from R). At a fixed posture, shear wave speeds decreased significantly from the free tendon to the gastrocnemius musculotendon junction, with slightly higher speeds measured on the medial side than on the lateral side. Shear wave speeds were only weakly correlated with the thickness and depth of the tendon, suggesting that the distal-to-proximal variations may reflect greater compliance in the aponeurosis relative to the free tendon. The results highlight the importance of considering both limb posture and transducer positioning when using SSI for biomechanical and clinical assessments of the Achilles tendon.

Lumbar annulus fibrosus biomechanical characterization in healthy children by ultrasound shear wave elastography

“…Measurement reliability and interobserver agreement for a single measurement was similar to the one previously obtained in adult cervical disc (0.2 -0.3 m/s) and in in vitro measurements (0.2 -0.4 m/s) [16; 19], and it was similar or better than those obtained in elastographic evaluation of other soft tissues (for instance, 6.8 % in lower limb muscles [27], 15.6 % in tendon [28], ICC = 0.87 in breast masses [29]). No operator effect was observed, which is not surprising since, unlike muscles, IVD is a deep structure and its measurement is not affected by probe pressure.…”

Shear-Wave Elastography: Basic Physics and Musculoskeletal Applications

“…The majority of these studies are experimental (5,6,(9)(10)(11)(12)(13)(14)(16)(17)(18)(19)(20)(21)(22)(23)(24)27,29,(31)(32)(33) with a smaller number of clinical studies (7,8,15,26,28,30,34,35). Additionally, several studies evaluated viscoelastic properties of the Achilles tendon (5)(6)(7)(8)(9)(10)(11)(12)(13)(14). The current literature suggests that shear waves propagate faster in healthy tendons than in those that are tendinopathic, and faster in contracted tendons and muscles than in those that are relaxed.…”

“…Several authors used SWE to evaluate the elasticity of normal and tendinopathic Achilles tendons in different postures (resting position, plantar flexion, dorsiflexion) and emphasized the importance of both spatial location and ankle posture with SWE for evaluation of viscoelastic properties of the Achilles tendon (6,7,10,17).…”

“…Promising results have been published in the recent literature on the utility of SWE in the evaluation of several traumatic and pathologic conditions of various musculoskeletal soft tissues, including tendons (5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17), muscles (18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29), nerves (30)(31)(32), and ligaments (33)(34)(35).…”

Non-uniform displacements within the Achilles tendon observed during passive and eccentric loading

“…For example, prior studies have used ultrasound-based manual tracking of anatomical landmarks to show that different amounts of strain are taken up by the free tendon and aponeurosis (Arampatzis et al, 2005; Magnusson et al, 2001; Magnusson et al, 2003; Muramatsu et al, 2001). Along-tendon non-uniform deformation could arise from variations in loading along the aponeurosis (Finni et al, 2003) as well as spatially varying tendinous tissue stiffness (DeWall et al, 2014). However, much less is known about spatial variations in tendon deformation across the tendon thickness.…”