An investigation into remodelling, morphological and mechanical changes in the clinical management of mid-portion achilles tendinopathy

Abstract

Mid-portion Achilles tendinopathy is a chronic degenerative tendon condition characterised by pain, impaired function and structural alterations that compromise tendon integrity, affecting both sedentary and active individuals. Despite its widely reported high prevalence, the remodelling process during treatment remains poorly understood. This research investigates Achilles tendon remodelling during rehabilitation and High-Volume Image Guided Injection treatment, focusing on mechanical and morphological property changes to improve clinical management and patient outcomes. Carried out in three phases, the research first identified gaps in clinical practice and assessment modalities through various reviews and a sequential mixed methods scoping study. The findings highlighted the insufficiency of relying solely on morphological evaluation and underscored the local needs for optimised referral pathways, objective outcome measures and multidisciplinary care integration. This led to the establishment of a multidisciplinary Sports and Exercise Clinic. In phase two, the research validated both shear wave elastography and myotonometry as methods for measuring small tendon strains, the latter emerging as the more pragmatic tool. This led to the development of a standardised reliability protocol for consistent monitoring of tendon mechanical properties during treatment and rehabilitation. Phase three employed a pragmatic, assessor-blinded randomised controlled trial comparing exercise rehabilitation alone to High-Volume Image Guided Injection combined with exercise. The findings suggest that although both groups achieved comparable pain reduction, the intervention group showed an early unexpected reduction in stiffness (t=-3.09(16), p=0.007), raising questions about the injection’s immediate mechanical effect on the tendon. Furthermore, tendon bulge thickness decreased significantly in the intervention group, though this change fell short of clinical significance suggesting that morphological changes may require longer period to manifest. These findings should be interpreted in light of the small sample size, which was justified by a higher prevalence of insertional tendinopathy (67.9%) compared to mid-portion tendinopathy (20.3%) in the study population - an observation linked to shorter free tendon length, which may represent a potential anatomical risk factor for insertional tendinopathy. This research provides novel insights into tendon remodelling and is the first to objectively quantify short-term mechanical stiffness post High-Volume Image Guided Injection, highlighting a previously underexplored aspect of treatment efficacy and underscoring the need for further studies to evaluate the injection’s long term biomechanical impact.