Analysis of Regional Heterogeneity of Mechanical Properties Improves Sensitivity of Elastography to Changes With Achilles Tendinopathy.

Abstract

Achilles tendinopathy is a prevalent condition resulting in pain, impaired performance, and multi-scale structural changes in the tendon. Achilles tendinopathy affects tissue properties of shear modulus and viscosity, typically reported as average changes across the tendon. However, tendinopathy is characterized by nonuniform pathology, indicating a need for new analytical tools to better assess heterogeneity in mechanical properties measured using continuous shear wave elastography (cSWE). This analysis included cSWE data measured bilaterally from 20 healthy participants and 121 participants with Achilles tendinopathy. Novel computational analyses were developed to quantify regional variability (i.e., heterogeneity) in shear modulus and viscosity throughout the tendon. Average value analysis revealed greater mean viscosity in healthy compared to tendinopathic tendons; likewise, in the less affected compared to the most affected tendons in participants with bilateral tendinopathy. No significant differences in shear modulus were observed when comparing average values. Demonstrating its enhanced sensitivity, regional analysis distinguished between the viscosity of healthy and tendinopathic tendons, and both viscosity and shear modulus regional analysis identified the most affected side in tendinopathic participants, unlike the standard average-based analysis. This novel heterogeneity analysis provides a deeper understanding of tendon mechanics in Achilles tendinopathy than previously accessible from cSWE measurements. These findings indicate that Achilles tendinopathy leads to a greater degree of variability in tissue mechanical properties, highlighting the importance of considering regional differences in tissue properties when evaluating this condition. This new method has the potential to improve the diagnosis and treatment of Achilles tendinopathy by identifying specific regions of tissue heterogeneity.