Flexor digitorum profundus evaluation in normal muscle mass subjects and presarcopenic patients - a sonoelastographic...

Presarcopenia represents the earliest stage of sarcopenia. While muscle ultrasound (US) and shear wave elastography (SWE) offer promise as a non-invasive tool, its role in detecting early muscle loss remains underexplored, especially in the upper limb. Therefore, the aim of this study was to characterize the flexor digitorum profundus (FDP) muscle in older adults with presarcopenia versus normal muscle mass, and to assess the diagnostic potential of grayscale echogenicity and SWE.

This cross-sectional study included 50 age- and sex-matched participants classified as presarcopenic (n=25) or normal muscle mass (n=25) based on dual-energy x-ray absorptiometry (DXA)-derived appendicular skeletal muscle mass index (ASMI). All underwent clinical evaluation and ultrasound assessment of the FDP. US parameters included cross-sectional area (CSA), muscle thickness (MT), pennation angle (PA), echogenicity, and SWE in relaxation and contraction. Logistic regression and ROC analysis were applied.

Presarcopenic participants had significantly lower CSA (p=0.001) and higher grayscale echogenicity (p<0.001). MT and PA did not differ significantly. Echogenicity showed negative correlations with CSA, DXA measurements, and forearm circumference (FC). Grayscale cut-off values were proposed to differentiate visual echogenicity grades. Although SWE values were not significantly different in univariate analysis, SWE in relaxation emerged as an independent predictor in the regression model.

FDP grayscale echogenicity is a strong marker of early muscle decline. SWE in relaxation independently predicted presarcopenia, supporting its role in early diagnostic frameworks. Larger studies are warranted.