Quantitative Ultrasound of the Enthesis in Fibromyalgia and Psoriatic Arthritis

In this prospective, cross-sectional, observational study consecutive eligible subjects with FM, PsA, and a group of age- and sex-matched asymptomatic volunteers will undergo a research US examination of the dominant Achilles' tendon, knee medial collateral ligament and common extensor tendon of the elbow. Two operators under the supervision of a musculoskeletal radiologist will perform the US exam. B-mode and Power Doppler ultrasound of each tendon and ligament will be performed for morphological characterization. Then, shear wave elastography (SWE) and radiofrequency (RF) will be acquired. The shear wave speed (SWS) will be measured in the longitudinal plane using shear wave measurements. These features will be compared between groups. The HDK parameters (μ, 1/alpha, κ) will be computed offline, using RF sequences recorded in the longitudinal plane. Demographic features (participant age, sex, body mass index), the Leeds Enthesis Index (LEI) score assessed by the referring clinicians, and the self-administered Health Assessment Questionnaire (HAQ), Brief Pain Inventory (PBI) and Fibromyalgia Impact Questionnaire (FIQ) scores will be available for multivariate analyses.