Efficacy of Two Ultrasound-guided Intra-articular Injections of Botox® Combined With Custom-made Rigid Splinting in Painful Base-of-thumb Osteoarthritis.

Inclusion Criteria: * • Individuals aged at least 18 years; * Pain intensity of at least 30 on a self-administered 11-point pain numeric rating scale (0: no pain to 100: maximal pain); * Pain involving the base of the thumb; * X-ray evidence of trapezometacarpial osteoarthritis with at least two of the following items involving the trapezometacarpial joint: osteophytes, joint space narrowing, subchondral bone sclerosis, or subchondral cysts; * 1990 ACR classification criteria for hand osteoarthritis adapted to trapezometacarpial osteoarthritis. * Patient able to give written informed consent prior to participation in the study * Affiliation with a mode of social security (profit or being entitled). * Negative pregnancy test in women of childbearing potential Exclusion Criteria: * • Secondary osteoarthritis; * History of thumb surgery, inflammatory or crystal-associated rheumatic disease, or epilepsy; * Uncontrolled dysphagia, pneumonia, cardiovascular diseases, or clinical or subclinical signs of neuromuscular transmission disorders; * Contra-indication to onabotulinumtoxinA; * Neurological disorders involving the hands other than carpal tunnel syndrome; * Collagen disorders involving the hands; * Osteoarthritis predominating at the scaphotrapezial joint on x-ray; * Bilateral trapezometacarpial osteoarthritis without a predominant painful side; * Hand or wrist trauma for up to 2 months; * Intra-articular treatments for up to 2 months; * Use of IM, IV or oral corticosteroids for up to 2 months. * Protected adults (including individual under guardianship by court order) * Pregnant women and lactation; lack of contraception for women of childbearing potential * Patient participating in another investigational therapeutic study * Patient unable to speak and read french