Altered patterns of displacement within the Achilles tendon following surgical repair

Abstract

PurposeUltrasound speckle tracking was used to compare tendon deformation patterns between uninjured and surgically repaired Achilles tendons at 14–27-month follow-up. The hypothesis was that the non-homogenous displacement pattern previously described in uninjured tendons, where displacement within deep layers of the tendons exceeds that of superficial layers, is altered following tendon rupture and subsequent surgical repair.MethodsIn the first part of this study, an in-house-developed block-matching speckle tracking algorithm was evaluated for assessment of displacement on porcine flexor digitorum tendons. Displacement data from speckle tracking were compared to displacement data from manual tracking. In the second part of the study, eleven patients with previous unilateral surgically treated Achilles tendon rupture were investigated using ultrasound speckle tracking. The difference in superficial and deep tendon displacement was assessed. Displacement patterns in the surgically repaired and uninjured tendons were compared during passive motion (Thompson’s squeeze test) and during active ankle dorsiflexion.ResultsThe difference in peak displacement between superficial and deep layers was significantly (p < 0.01) larger in the uninjured tendons as compared to the surgically repaired tendons both during Thompson’s test (−0.7 ± 0.2 mm compared to −0.1 ± 0.1 mm) and active dorsiflexion (3.3 ± 1.1 mm compared to 0.3 ± 0.2 mm). The evaluation of the speckle tracking algorithm showed correlations of r ≥ 0.89 between displacement data acquired from speckle tracking and the reference displacement acquired from manual tracking. Speckle tracking systematically underestimated the magnitude of displacement with coefficients of variation of less than 11.7%.ConclusionsUninjured Achilles tendons display a non-uniform displacement pattern thought to reflect gliding between fascicles. This pattern was altered after a mean duration of 19 ± 4 months following surgical repair of the tendon indicating that fascicle sliding is impaired. This may affect modulation of the action between different components of the triceps surae, which in turn may affect force transmission and tendon elasticity resulting in impaired function and risk of re-rupture.

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

“…The settings we chose were based on trial and error to find somewhat optimal settings for our heel‐rise recordings. Previous studies have reported similar results showing the speckle algorithm being a bit conservative . Others have performed a similar validation of the speckle tracking method in an in vitro animal model and reported a mean tracking error of 1.6%, which is close to the data of the present human in vivo study.…”

“…Previous studies have reported similar results showing the speckle algorithm being a bit conservative. 12 Others 11 have performed a similar validation of the speckle tracking method in an in vitro animal model and reported a mean tracking error of 1.6%, which is close to the data of the present human in vivo study. A: Data are presented as the mean AE SD (pixel) displacement for the 4 rows tracked at 2 separate recordings of the same exercise.…”

“…Tracking on the proximal bead, most distant to the ruptured area turned out to be beneficial regarding keeping the transducer in line of tendon fascicles as the twisting nature often were located more distal to this. The frame‐rate was set at 42 FPS and thereby lower compared to similar studies . However, the pace of contraction was 3 seconds for each phase and the displacements were around 300 pixels, so approximately 100 pixels displacement per second.…”

The challenges of measuring in vivo knee collateral ligament strains using ultrasound

“…To date, speckle-tracking studies have focused almost exclusively on large energy-storing tendons such as the Achilles (Arndt et al, 2012; Brown et al, 2013; Å. Fröberg et al, 2016; Nuri et al, 2016; Slane and Thelen, 2015, 2014b) and patellar (Lee et al, 2016; Pearson et al, 2014; Slane et al, 2017) tendons, with motivations often cited as their propensity for injury. However, there are also many practical advantages to studying these tendons, that thereby constitute complications when assessing the collateral ligaments.…”

“…This then requires smaller regions-of-interest (ROIs) for tracking, which can be prone to mismatch as well as lower repeatability and accuracy than larger ROIs (Fröberg et al, 2016). Further, the small varus/valgus range of motion means small frame-to-frame motion.…”