Achilles tendinopathy is a debilitating overuse injury that is characterized by pain during loading activities, swelling, and impaired functional performance. The incidence rate in the adult population is 2.35 per 1000, with middle-aged adults (i.e. 30–50 years old) who are physically active being the most frequently affected. Throughout rehabilitation, patient-reported symptoms are commonly used to monitor recovery and tailor treatment. However, a rehabilitation program that solely focuses on symptoms may be problematic since the resolution of symptoms does not ensure the structure or function of the tendon has normalized. With 41% of patients continuing to have symptoms after 8 years and up to 29% undergoing surgery, a more comprehensive approach to rehabilitation is needed to improve long-term patient outcomes. Measures of tendon morphology and mechanical properties may provide critical information regarding the health of the tendon that can be used to supplement patient-reported symptoms. Before these measures can be implemented in clinical practice, there is a need to determine if tendon morphology and mechanical properties relate to the patient symptoms and function. Therefore, the purpose of this dissertation work was to determine if tendon morphology and mechanical properties play a critical role in recovery for patients with Achilles tendinopathy.
The first aim of this dissertation work was to assess the reliability and validity of measuring in vivo mechanical properties with continuous shear wave elastography (cSWE) in healthy and degenerative Achilles tendons. Our findings support the use of cSWE for monitoring changes in tendon mechanical properties, with fair-to-excellent intrarater reliability for all properties. The second aim was to determine if tendon morphology and mechanical properties were associated with recovery of patient-reported symptoms and functional performance. This was performed by prospectively following a cohort of patients with Achilles tendinopathy for one year. The key findings were 1) greater tendon thickening was associated with worse symptoms and calf muscle function 2) patient-reported symptoms over the year depended on the initial shear modulus of the tendon and 3) worse calf muscle function was associated with lower viscosity. These results indicate that Achilles tendon morphology and mechanical properties are predictive of long-term symptoms and function in patients with Achilles tendinopathy. The goal of the third aim was to evaluate the immediate effects of laser-induced photobiomodulation therapy on Achilles tendon morphology and mechanical properties in healthy and degenerative tendons. Results demonstrated that laser therapy does not have immediate effects on the Achilles tendon, which suggests that laser therapy can be administered at any time during a treatment session without influencing other treatments. Lastly, in aim 4 we explored the relationships between patient-reported outcomes, tendon morphology, mechanical properties, lower leg function, pain, and running mechanics in patients with Achilles tendinopathy. We found that pain and lower leg functional performance were associated with Achilles tendon loading patterns while running, but patient-reported outcomes, tendon morphology and mechanical properties were not.
Collectively, this dissertation work supports the use of cSWE for estimating tendon mechanical properties, identifies the importance of tendon morphology and mechanical properties in symptom and functional recovery, and elucidates aspects of tendon health that may be critical when progressing patients with Achilles tendinopathy from return-to-sport to return-to-performance.
|Advisor:||Grävare Silbernagel, Karin|
|Commitee:||Higginson, Jill S., Willy, Richard W., Swanik, C. Buz|
|School:||University of Delaware|
|Department:||Biomechanics and Movement Science|
|School Location:||United States -- Delaware|
|Source:||DAI-B 81/4(E), Dissertation Abstracts International|
|Keywords:||Achilles tendon, Elastography, Rehabilitation, Tendinitis, Tendinopathy, Ultrasound|
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