Achilles Tendinopathy – Sonographic Features, Correlation with Clinical Outcomes and Injection Therapy

Introduction
Achilles tendinopathy refers to the clinical disease characterised by tendon pain and swelling that results in impaired performance. Chronic tendinopathy can be a significant problem, especially in the sporting population. Even though sonographic investigation is commonly used to assess the structural integrity of the Achilles tendon, there is variability within the literature on how to accurately and reliability assess the Achilles tendon using ultrasound. This has led to a general lack of consistency in defining tendinopathic changes. Previous studies have cited a lack of a gold standard as a major limitation to Achilles tendinopathy assessment and research. There is an inconsistent and often weak relationship between sonographic findings and severity of clinical symptoms. To date, there have been no studies quantitatively assessing tendon grey-scale and Doppler sonographic appearances and comparing these to a validated outcome measure of symptomology.

The primary goal in the management of Achilles tendon disease is to return patients to their desired level of activity without significant residual pain. When conservative treatment fails, injection therapy is often offered. There are various injectable therapies currently being employed for the treatment of recalcitrant Achilles tendinopathy, yet only sparse scientific evidence exists to support any specific injection treatment. High-volume peritendinous glucocorticoid injections are one such injection method growing in popularity, with early studies showing promising results. The aim of these injections are to mechanically disrupt (by stretching, breaking or occluding) the neurovascular bundles growing from the paratenon into the tendon. Additional to injection therapy, appropriate load management of the tendon has been shown to be the most successful long-term intervention. Therefore, it was hypothesised that the combination of a large-volume peritendinous glucocorticoid injection with a graded functional loading program from a physiotherapist would lead to an improvement in outcomes for patients with recalcitrant Achilles tendinopathy.

Methodology
An expert panel of professionals (Delphi panel) was formed with extensive knowledge and experience in the assessment of tendinopathy using ultrasound. This combined with a thorough literature review led to the development of the Achilles ultrasound assessment tool (AUAT). The AUAT is a numeric scoresheet that holistically assesses the entire spectrum of sonographic changes present within the tendinopathic tendon and peritendinous tissues, allowing semi-quantification of the appearance of these structures.

The construct validity, reliability and repeatability of the AUAT were assessed by evaluating the level of agreement between 6 sonographers and 6 radiologists assessing the same sonographic images from 4 different patients. Whilst, sonographic correlation with clinical outcomes was assessed by exploring the relationship between AUAT scores with a validated index for the clinical severity of Achilles tendinopathy, the Victorian Institute of Sport assessment – Achilles (VISA-A) questionnaire. A cohort of 43 participants with chronic Achilles tendinopathy elected to undergo a single high-volume peritendinous glucocorticoid injection in combination with a supervised rehabilitation program. Patients were injected with 1mL celestone chronodose combined with 2mL xylocaine and 20mL of cold normal saline. Blinded assessors evaluated participants pre-intervention and at 24-week follow-up sonographically using the AUAT and clinically with the VISA-A.

Results
The AUAT was able to differentiate sonographically normal tendons from abnormal (κ = 0.481, p < 0.001), even in tendons with only mild sonographic changes. Inter-observer reliability showed almost perfect levels of agreement between both sonographer and radiologist groups (κ = 0.949, p < 0.001), while intra-observer reliability showed no significant difference between initial and subsequent AUAT assessments (p > 0.05).

The results of the correlation of the AUAT with clinical findings are conflicting, with no association at initial presentation (rs = -0.04, p > 0.05) between AUAT score and the clinical score of symptomology, the VISA-A. Yet at 24-week follow-up of the same patient cohort after intervention, a significant moderate strength relationship existed (rs = -0.56, p > 0.001).

For the management of recalcitrant Achilles tendinopathy, a single high-volume ultrasound guided peritendinous injection significantly reduced pain and improved function when combined with exercise therapy. This clinical improvement assessed by the VISA-A (p > 0.001) coincided with a sonographic improvement in tendon morphology as assessed by the AUAT (p > 0.001).

Conclusion
The AUAT is a valid and reliable tool to define and represent the sonographic changes involved in Achilles tendinopathy and possesses the potential to be a useful instrument when evaluating the status and progress of Achilles tendon disorders. The construct validity of the AUAT via its Delphi formation along with its high levels of inter and intra observer reliability demonstrate the strengths and clinical applicability of this tool. The relationship of the AUAT to clinical symptoms is variable, with this study contributing to the growing body of evidence that there is a disconnect between structure and pain. In recalcitrant Achilles tendinopathy, a single high-volume peritendinous glucocorticoid injection leads to a significant reduction in pain and improvements in both function and tendon sonographic appearance.