Prospective Evaluation of Changes in Elastic Properties of Ruptured Achilles Tendons by Shear Wave Elastography

Purpose:

Biomechanical properties of tendon change after rupture. Shear wave elastography (SWE) allows evaluating biomechanical properties ('elastografic stiffness') of soft tissue. The main objective of this study was to show the development of changes in elastic properties of the Achilles tendon (AT) in the early healing phase after rupture. Further objectives were to examine a correlation between the patients' subjective outcome and changes in the elastic properties and to compare non-operatively vs. operatively treated tendons.

Methods:

SWE was performed on ATs of patients who had ruptured their AT and received operative (O) or non-operative (N) treatment at stated intervals (1, 3, 6, 9 and 12 weeks after injury). Patients were included who presented at our emergency department with an isolated partial or total rupture of the AT. Exclusion criteria were bi-lateral injury in their history, arthrodesis of one of the upper ankle joints, neuropathic or malignant diseases, age < 18 years. Both AT (injured and healthy) of each patient were scanned in the distal, middle and proximal portion as well as in the rupture area (of the injured tendon respectively) using Virtual TouchTM IQ sonography (Siemens Acuson S3000, 4 – 9 MHz linear probe). For evaluation of the patients' outcome two established functional scores were used. Statistical analysis was performed by using linear regression analysis for the different time points and paired t-test for independent samples.

Results:

12 patients were included in the study by the time of abstract submission [9 (N), 3 (O)]. Results indicate a positive linear regression between shear wave velocity at the rupture site and time after injury [R2 = 0.697, p < 0.001]. A significant difference in stiffness was found between O and N after 3 weeks at the rupture site [p = 0.025]. 6 weeks after injury the rupture site gains values equally to the contralateral tendon. No significant correlation was found between SWE and functional outcome.

Conclusion:

Quantitative SWE is capable of displaying changes in elastic properties during tendon healing. Furthermore, a noticeable increase of elastografic stiffness especially between 3 and 6 weeks after injury was shown after an initial absence of elastografic stiffness in the first weeks after injury. Further analyses need to be done in order to correlate ultrasound findings with clinical scores and biomechanical parameters. To assess the utility of SWE for monitoring purposes more studies are necessary.

Fig. 1: Positive linear regression between shear wave velocity at the rupture site and time after injury [R2=0.697, p<0.001]