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What Is the Trapezium?

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  • Written By: Mike Howells
  • Edited By: Michelle Arevalo
  • Last Modified Date: 14 April 2014
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The trapezium is a bone located in the wrist of each arm on the human body. It is situated between the wrist and the finger bones in the hand, which are called the first metacarpals. The trapezium, or greater multangular bone as it is referred to in Gray's Anatomy, is itself is about the size of a pebble and roughly quadrilateral in shape, with a large groove on one side.

With the hand and wrist second only to the foot in terms of bone complexity, the trapezium is one of a number of small bones that are known as the carpal bones. Each of the carpal bones must function correctly to ensure proper hand strength, flexibility, and pain-free articulation. The rest of the carpal bones include the scaphoid, the lunate, the triquetral, the pisiform, the trapezoid, the capitate, and the hamate. The first four of these bones are known as the proximal carpal bones, since they are located closer to the wrist joint. The last three, as well as the trapezium, are called the distal carpal bones, and are closer to the hand.

The trapezium articulates directly with the scaphoid and the trapezoid bones close to the wrist, and also with the first metacarpal bone of the thumb, towards the hand. Given its hinge-like nature, it is an important bone, despite its small size. Specifically, the trapezium bone is notable in that it is the subject of a somewhat controversial medical procedure that involves its removal to alleviate severe arthritis pain.

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The joint between the first metacarpal of the thumb and the greater multangular bone is known as the carpometacarpal joint (CMC). It allows the thumb to swivel, bend, and clasp things. Given its heavy use, it is not uncommon for the CMC joint to wear out relatively early in life, even in people who do not otherwise suffer from arthritis. A worn CMC joint causes pain and loss of strength, as the previously cushioned bones begin scraping against one another.

If more conservative treatment, such as anti-inflammatory drug prescriptions, regular icing, and splints, do not resolve the pain, some doctors may authorize surgery to remove the trapezium. Tendons are grafted in to the space vacated by the bone, which then serve as a cushion between the CMC joint and the rest of the hand. Following four to six weeks of wearing a splint, and then roughly another six months of rehabilitation, many patients recover full strength in the affected hand. Critics of this technique say it is a bad idea, given that it permanently alters the biomechanics of the hand, despite what pain relief may initially result.

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