Ultrasound assessment of diaphragm and quadriceps muscles and its relationship with handgrip and respiratory muscle strength in patients with systemic sclerosis: a cross-sectional study

Background Muscle dysfunction may cause disability and reduce the quality of life of patients with systemic sclerosis (SSc) when compared to healthy individuals. However, the literature on the topic is scarce and uses several criteria for assessing muscle dysfunction in this population.Objectives To compare diaphragm and quadriceps muscle thickness, diaphragm mobility, and handgrip strength between patients with SSc and healthy individuals.Method This cross-sectional study included 16 patients with SSc and 16 self-reported healthy individuals matched for age. We assessed quadriceps and diaphragm thickness and diaphragmatic mobility (ultrasound), handgrip strength (hand-held dynamometer), and respiratory muscle strength (manovacuometer). Patients also responded to the Health Assessment Questionnaire Disability Index and the International Physical Activity Questionnaire.Results Patients with SSc presented lower quadriceps thickness (p < 0.0001), diaphragmatic mobility (p = 0.01), handgrip (p < 0.0001), and respiratory muscle strength (p < 0.0001) than healthy individuals. A moderate positive correlation was observed between handgrip strength and quadriceps thickness in patients with SSc (rho = 0.576; p = 0.02).Conclusions Patients with SSc presented reduced quadriceps thickness, diaphragmatic mobility, handgrip, and respiratory muscle strength when compared to healthy individuals Also, handgrip strength was correlated with quadriceps thickness in patients with SSc, suggesting that loss of muscle mass accompanies loss of peripheral muscle strength group of patients.