Multimodal ultrasound in the assessment of muscle involvement in systemic sclerosis patients: results from a bicentric study

Objective: To investigate muscle mass, quality, and stiffness using ultrasound ('multimodal ultrasound') in systemic sclerosis (SSc) patients, compared with healthy controls (HCs), and examine their correlation with muscle strength, physical performance, and disability. Methods: In this cross-sectional, bicentric study (Jesi and Leeds), ultrasound scans of the quadriceps muscle (QM) were performed in SSc patients (without inflammatory myositis) and HCs to assess muscle mass, quality [using a semi-quantitative modified Heckmatt scale (mHS) and grey-scale histogram analysis (GSA) for muscle echogenicity], and stiffness [measured by shear-wave elastography (SWE)]. Muscle strength was assessed using the handgrip test, physical performance was evaluated with the Short Physical Performance Battery, and disability was measured using the Health Assessment Questionnaire. Results: A total of 81 SSc patients (36 from Jesi, 45 from Leeds) and 24 HCs (Jesi) were included. After adjusting for age, SSc patients showed increased muscle echogenicity-measured by mHS and GSA (the latter in Jesi cohort; p< 0.001)-and lower SWE values (Jesi cohort, p< 0.001), with no significant difference in muscle mass (p= 0.433). Higher QM muscle thickness values significantly correlated with better strength, physical performance, and lower disability. Increased muscle echogenicity (i.e. low muscle quality) significantly correlated with poorer strength, worse physical performance, and higher disability. Higher SWE values in the Jesi cohort significantly correlated with better strength, performance, and lower disability, while 2D SWE in the Leeds cohort showed reduced strength but no link to disability. Conclusions: Ultrasound demonstrated its potential for detecting early, clinically significant changes in muscle mass, quality and stiffness in SSc patients.