Because of its relative instability, this joint is a frequent site for osteoarthritis. This joint is formed by the trapezium bone of the wrist and the first metacarpal bone of the thumb. Your trapezium is a small bone at the base of your wrist that joins your thumb to your wrist. Wear and tear within this joint can cause pain. The opponens pollicis muscle extends from the trapezium bone of the wrist and the flexor retinaculum in the heel of the hand to wrap partially around, and attaches to the first metacarpal bone. Arthrodesis eliminates pain by fusing the bones in the joint together. Trapeziometacarpal osteoarthritis, also known as osteoarthritis at the base of the thumb or as rhizarthrosis, is a reparitive joint disease affecting the first carpometacarpal joint (CMC1). Structure. 5.2). Surgeons create a socket by hollowing out the thumb’s metacarpal bone and then shaping the trapezium into a cone that fits inside the socket. If conservative treatment methods are not successful your consultant may recommend a trapeziectomy. Then, I will gently remove the small bone at the base of the thumb (the trapezium); this bone is the cause of your pain. A metal pin holds bones together to maintain proper alignment and prevent movement while the bones fuse. The trapezium is an irregular-shaped carpal bone found within the hand. Patients present with symptoms of pain and tenderness over the base of the thenar eminence and with thenar pain upon resisting wrist flexion. Occasionally if there is arthritis at the base of the trapezoid (a neighbouring carpal bone), then I will remove the arthritic part of this bone as well. It is situated at the radial side of the carpus, between the scaphoid and the first metacarpal bone (the metacarpal bone of the thumb). Surfaces. The surrounding joints are inspected at the same time. The trapezium is distinguished by a deep groove on its anterior surface. Anatomy: The adductor pollicis muscle originates in the carpometacarpal region of the index and middle fingers, to the base of the proximal phalanx of the thumb. The author retrospectively reviewed 100 CT scans of the wrist, ordered for a suspected scaphoid fracture, and in 6 cases there was a fracture of the ridge of the trapezium ( Fig. It is homologous with the first distal carpal of reptiles and amphibians..