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The TMC joint is a synovial joint between the trapezium bone of the wrist and the metacarpal bone at the base of the thumb. This joint is a so-called saddle joint (articulatio sellaris), unlike the CMC joints of the other four fingers which are ellipsoid joints. [17] This means that the surfaces of the TMC joint are both concave and convex.
The carpometacarpal (CMC) joints are five joints in the wrist that articulate the distal row of carpal bones and the proximal bases of the five metacarpal bones.. The CMC joint of the thumb or the first CMC joint, also known as the trapeziometacarpal (TMC) joint, differs significantly from the other four CMC joints and is therefore described separately.
The radial collateral ligament (external lateral ligament, radial carpal collateral ligament) extends from the tip of the styloid process of the radius and attaches to the radial side of the scaphoid (formerly navicular bone of the hand), immediately adjacent to its proximal articular surface and some fibres extend to the lateral side of the trapezium (greater multangular bone).
The bones closer to the forearm (proximal) are removed: scaphoid, lunate, and triquetrum. [14] It is important that the radioscaphocapitate ligament is left intact, because if the ligament is not preserved the capitate bone will translate to the ulnar side of the wrist and move away from the distal radius. [1] [15]
The trapezium is an irregular-shaped carpal bone found within the hand. The trapezium is found within the distal row of carpal bones, and is directly adjacent to the metacarpal bone of the thumb. On its ulnar surface are found the trapezoid and scaphoid bones. [1]: 708
Isolated fractures of the trapezoid are rare, representing 0.4% of the total, thus being the least common of all carpal fractures. This is due to the bone being in a fairly protected position. Distally, it forms a stable, relatively immobile joint with the second metacarpal, radially and proximally it forms strong ligaments with the trapezium ...
In a case where there is localized tenderness within the snuffbox, knowledge of wrist anatomy leads to the speedy conclusion that the fracture is likely to be of the scaphoid. This is understandable as the scaphoid is a small, oddly shaped bone whose purpose is to facilitate mobility rather than confer stability to the wrist joint [citation ...
Optimal wrist function requires stability of the carpal components in all joint positions under static and dynamic conditions. Stability is achieved by a sophisticated geometry of articular surfaces and intricate system of ligaments, retinacula, and tendons, which also determine the relative motion of the carpal bones.