Ultrasound tissue characterization and function of Achilles tendon in psoriatic arthritis patients: a cross-sectional study

BACKGROUND: The Achilles tendon is one of the most frequent sites of tendinopathy in both healthy and pathological subjects. An innovative approach for the quantitative assessment of the Achilles tendon structure, named Ultrasound Tissue Characterization (UTC), has recently been developed. However, no previous study performed the UTC-based assessment of the tendon structure in rheumatologic patients affected by insertional Achilles tendinopathy. AIM: To characterize the Achilles tendon structure and function in psoriatic arthritis patients with symptomatic insertional tendinopathy DESIGN: Cross-sectional study. SETTING: University laboratory. POPULATION: Psoriatic arthritis patients (n=17). METHODS: Anthropometric measurements, administration of outcome and pain questionnaires, and tendon function and structure assessments were performed in a single experimental session. RESULTS: Pain intensity and interference and the perceived tendinopathy-related disability were moderate-severe. A relevant impairment of the strength (for both lower limbs) and walking performance was observed in all patients. In fact, the plantarflexion strength values (median values for the two sides: 10.0 and 11.5 kg) and fast walking speed (median value: 1.7 m/s) were lower than the normative values for healthy controls, respectively, in all patients for the strength values and in 14 out of 17 patients for the walking speed. The conventional ultrasound (i.e., the quantification of tendon thickness and the qualitative assessments of tendon structure and neovascularization) showed greater changes in the symptomatic (or more symptomatic) side compared with the asymptomatic (or less symptomatic) side of the insertional region of the Achilles tendon. The UTC imaging showed comparable impairment of the tendon structure between the symptomatic (or more symptomatic) side and the asymptomatic (or less symptomatic) side of the insertional region of the Achilles tendon (i.e., reduced echo-type I percentages in both tendons of all patients). CONCLUSIONS: Psoriatic arthritis patients with symptomatic insertional Achilles tendinopathy present moderate-severe pain and perceived disability, physical function impairments, and bilateral deterioration of the tendon structure (also in case of unilateral symptoms) that can be documented through the UTC analysis.