Regional alterations in Achilles tendon morphology in elite adolescent athletes with Achilles tendinopathy compared to matched controls.

OBJECTIVES

The study aims to analyze intra-tendinous micro-morphology measured with ultrasound image spatial frequency analysis in adolescent athletes with unilateral Achilles tendinopathy but without signs of tendon pathology on conventional ultrasound images.

DESIGN

Cross-sectional study.

METHODS

In this retrospective analysis of medical and tendon data from n = 1043 adolescent athletes, 31 cases diagnosed with Achilles tendinopathy were recruited. Datasets reporting bilateral symptoms, presence of image-based tendon pathology or inadequate imaging quality were excluded. Twenty-one adolescent athletes with Achilles tendinopathy were included. Subsequently, 21 age- and sport-matched pain-free controls with inconspicuous tendons on imaging were added from the database. Spatial frequency analysis with 8 parameters was performed on standard regions of interest at the tendon attachment and midportion. Additionally, the region of interest of structural irregularities at painful sites was investigated. Lower values of spatial frequency analysis parameters indicate increased fiber disorganization, and lower fiber density. Calculated parameters were compared using ANOVA (α < 0.05).

RESULTS

The painful site showed significantly lower values in two parameters indicating fiber organization (p < 0.03) and one indicting fiber density (p < 0.01) compared to both standard regions of interest of the same tendon and the contralateral asymptomatic tendon. Compared to matched control tendons decreased values were seen for the painful site versus three parameters indicating fiber organization (p < 0.05) and one indicting fiber density (p < 0.01).

CONCLUSIONS

Adolescent athletes with Achilles tendinopathy present altered intra-tendinous morphology at the painful tendon site. Conversely, standard regions of interest revealed comparable values to previous findings in healthy tendons of adolescent athletes. The results indicate that painful tendons, devoid of degeneration on B-mode ultrasound, have increased fiber disorganization and lower density, representing reactive tendinopathy.