Thumb Muscle Activation During First Dorsal Interosseous Activities of Daily Living in Thumb Base Osteoarthritis

The aim of this study is to investigate whether there are differences in muscle activation of the First Dorsal Interosseous (FDI) and the Abductor Pollicis Longus (APL) between individuals with and without trapeziometacarpal osteoarthritis (TMC OA) of the thumb during the performance of six activities of daily living (ADLs). The FDI has been defined as a key stabilizer of the TMC joint of the thumb. However, the literature reports limited information on FDI and APL activation during ADLs. TMC OA of the thumb can cause pain, decreased thumb strength, impaired hand function, and difficulty performing ADLs. Understanding muscle activation patterns during these activities is essential to comprehend how this condition affects hand function and to guide more specific and effective rehabilitation strategies. Participants will perform six ADLs: turning a key to open, turning a key to close, picking up a coin, writing, squeezing a tube of toothpaste, and holding a glass of water. Muscle activity will be recorded using surface electromyography (sEMG) during all tasks. Adults aged 30 years and older, both men and women, with TMC osteoarthritis and healthy controls without osteoarthritis will be invited to participate. Researchers will measure the activation patterns of the FDI and APL muscles during the ADLs, with the aim of identifying differences between both groups and providing evidence to guide the rehabilitation of patients with thumb base osteoarthritis.

Inclusion criteria for the TMC OA group: \- Clinical diagnosis of thumb TMC osteoarthritis. Inclusion criteria for the healthy group: \- Participants with no history of musculoskeletal or neurological disorders affecting the dominant hand were included. Exclusion Criteria : * Presence of numbness, tingling, or other sensory disturbances * Cardiac pacemaker implantation * Upper limb entrapment neuropathy or cervical radiculopathy * History of neuromuscular disease, polyneuropathy, or plexopathy * Systemic diseases such as diabetes, hypothyroidism, or chronic liver or kidney disease * History of cancer, rheumatoid arthritis, active anticoagulation therapy, chemotherapy, or exposure to neurotoxins * Recent upper limb soft tissue or bone injury (trauma, fracture, or surgery of the arm or neck).