Spatial Frequency Analysis Identifies Altered Local Micromorphology In Adolescent Athletes With Achilles Tendinopathy

Abstract

Site specific intratendinous Achilles morphology measured with ultrasound image spatial frequency analysis (SFA), quantifies the degree of collagen fiber density and organization. As tendon pain varies in location, and is not always related to hypoechogenicity, it is of interest to establish if spatial frequency parameters discriminate regions of tendon pain where hypoechoic alterations are not readily observable. PURPOSE: This study aims to analyze intratendinous micromorphology in adolescent athletes (AA) with Achilles tendinopathy and without sonographic evidence of tendinosis. METHODS: 22 AA (14m/8f, 13.2±1.4 y, 161±11 cm, 47±11 kg) with Achilles tendinopathy (history of tendon pain and pain on palpation) and no visible sonographic hypoechogenicity or focal tendon thickening were included in this analysis. Longitudinal ultrasound scans of the Achilles tendon were acquired. SFA was performed on regions of interest (ROI) corresponding to tendon pre-insertion and midportion, as well as the site of subjectively-reported tendon pain on palpation. Higher values of SFA parameters suggest greater collagen fiber density and alignment. Calculated SFA parameter values were compared using a one-factorial or Wilcoxon ANOVA (α<0.05). RESULTS: Significantly lower values for three SFA parameters were found at the symptomatic area as compared to tendon pre-insertion ROI, and for two parameters at the symptomatic area as compared to tendon midportion ROI (Table 1). CONCLUSION: As indicated by SFA, intratendinous morphology was altered at the painful area, whereas standard ROIs reveal comparable values to previous findings in healthy AA. These results indicate that painful, yet sonographically inconspicuous regions of tendons, have lower fiber density and alignment.Table 1:: SF parameters at tendon pre-insertion (I), midportion (M), and pain site (P) [mean ± SD]