Shear Wave Elastography for the Assessment of Thenar Muscle Elasticity in Trapeziometacarpal Osteoarthritis: A Cross-Sectional Study.

Purpose: Although recent studies have emphasized the importance of the adductor pollicis (AdP) and first dorsal interosseous (FDI) muscles in maintaining trapeziometacarpal (TMC) joint function, the viscoelastic properties of these muscles in the presence of TMC osteoarthritis (OA) remain unclear. This study aimed to investigate differences in the elasticity of the AdP and FDI muscles in patients with TMC OA, thereby contributing to the understanding of muscular changes associated with the disease.

Methods: Eighteen patients with TMC OA (29 thumbs) and 13 age- and sex-matched asymptomatic controls (26 thumbs) were included. The elasticity of the AdP and FDI muscles was measured using shear wave elastography (SWE). Data were analyzed using a linear mixed-effects model to assess differences between the groups.

Results: SWE values of the AdP muscle were notably higher in patients with TMC OA compared with controls, whereas no notable difference was found in the FDI muscle.

Conclusions: SWE provides a quantitative and real-time method for assessing the thenar muscle elasticity and detecting changes in the AdP muscle in TMC OA. Our findings suggest that shear wave elastography may be a promising tool for investigating biomechanical mechanisms involved in the pathogenesis of TMC OA.

Clinical relevance: SWE may inform clinical decision-making by identifying changes in the viscoelastic properties of the thenar muscles, which could support the assessment of muscle-targeted interventions in TMC OA.