Speckle tracking in healthy and surgically repaired human Achilles tendons at different knee angles-A validation using implanted tantalum beads

Abstract

The exact injury mechanism of Achilles tendinopathy remains unknown, but sliding of fascicles relative to each other during loading may be an important factor. This study validated the motion of ultrasound speckles against actual tendon movement using tantalum beads as reference markers. In addition, the effect of different knee joint angles (ie, muscle activation) on tendon tissue shear and displacement during a single heel rise was investigated. The 10 male participants had tantalum beads inserted in the tendon during surgery for a unilateral Achilles tendon rupture at least 1 year prior to the study. Ultrasound speckle displacement in the tissue surrounding the bead correlated strongly with displacement of the bead (R2 ≥ .9987). Speckle tracking systematically underestimated the displacement of the tendon tissue with a typical error of 1.1%-2.7%. There was a significant difference in displacement between the superficial and deep tendon layer for the 3 exercises in the healthy, but not in the surgically repaired Achilles tendon. The displacement difference was significantly greater when performing heel rises with the knee flexed 100° compared to knee flexed 40°. In conclusion, speckle tracking appears to be a valid approach to investigate intratendinous displacement.