Axial-strain sonoelastography of the Achilles tendinopathy: diagnosis, prevention and treatment monitoring

Compression elastography or axial-strain sonoelastography (SE) is a relatively new ultrasound (US) based technique that estimates the stiffness or softness of a tissue by measuring the strain (displacement) caused by tissue compression. Axial-strain SE allows characterization of the differences in stiffness between the region of interest and the surrounding tissue in a large range of lesions and pathologies. To date, several studies applying axial-strain SE to assess Achilles tendinopathy, patellar tendinopathy and common extensor tendinopathy have been published with conflicting results. The discrepancy in results reported between publications raising questions regarding its reproducibility. Moreover, there are still limited data regarding the diagnostic role of SE. This thesis builds upon previous work, evaluating the applications of axial-strain SE for the diagnosis of Achilles tendinopathy, assessing the risk of developing future symptoms and monitoring the disease progression and the efficacy of intervention. Our preliminary results demonstrated that the supplementation of axial-strain SE to traditional US imaging achieved a higher sensitivity and accuracy than routine combination technique of Colour Doppler and B-mode US. The semi-quantitative strain-ratio measurement was more related to the Achilles tendon pain and functional disability compared to conventional B-mode US. The results are clinically relevant as it may allow accurate and timely diagnosis of tendon injuries, which, in turn, allow early management planning and minimise possible tendon disability. Another important contribution of this thesis was the identification of sonographic predictors for the development of Achilles tendon injuries. Intratendinous delaminations and soft tendon properties as well as increased thickening and cross-sectional area were the potential risk factors for clinically manifesting Achilles tendon pain in elite athletes. Conventional US supplemented with axial-strain SE may be able to identify at risk athletes and allow early initiation of rehabilitative protocols to prevent further tendon damage. In addition, our research has shown that following therapy, the treated Achilles tendons showed progressive stiffening in relation to the Kager’s fat, coinciding with improvement in clinical findings up to one year follow-up. This highlights the potential clinical utility of axial-strain SE as supplementary tool in routine monitoring of Achilles tendon healing after treatment. We believe the work presented in this thesis will facilitate the use of axial-strain SE for diagnosis and management of Achilles tendon injuries in routine clinical setting.