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Carpometacarpal Articulation of the Thumb
This is a joint of reciprocal reception between the first metacarpal and the trapezium; it enjoys great freedom of movement on account of the configuration of its articular surfaces, which are saddle-shaped.
The joint is surrounded by a capsule, which is thick but loose, and passes from the circumference of the base of the metacarpal bone to the rough edge bounding the articular surface of the greater trapezium; it is thickest laterally and dorsally, and is lined by synovial membrane.
In this articulation the movements permitted are flexion and extension in the plane of the palm of the hand, abduction and adduction in a plane at right angles to the palm, circumduction, and opposition.
It is by the movement of opposition that the tip of the thumb is brought into contact with the volar surfaces of the slightly flexed fingers.
This movement is effected through the medium of a small sloping facet on the anterior lip of the saddle-shaped articular surface of the greater multangular.
The flexor muscles pull the corresponding part of the articular surface of the metacarpal bone on to this facet, and the movement of opposition is then carried out by the adductors.
Flexion of this joint is produced by the flexor pollicis longus and brevis, assisted by the opponens pollicis and the adductor pollicis.
Extension is effected mainly by the abductor pollicis longus, assisted by the Extensores pollicis longus and brevis.
Adduction is carried out by the Adductor; abduction mainly by the abductor pollicis longus and brevis, assisted by the extensors.
Articulations of the Other Four Metacarpal Bones with the Carpus
The joints between the carpus and the second, third, fourth, and fifth metacarpal bones are arthrodial.
The bones are united by dorsal, volar, and interosseous ligaments.
The Interosseous Ligaments
The interosseous ligaments consist of short, thick fibers, and are limited to one part of the carpometacarpal articulation; they connect the contiguous inferior angles of the capitate and hamate with the adjacent surfaces of the third and fourth metacarpal bones.
The synovial membrane is a continuation of that of the intercarpal joints. Occasionally, the joint between the hamate and the fourth and fifth metacarpal bones has a separate synovial membrane.
The synovial membranes of the wrist and carpus are thus seen to be five in number.
Occasionally the fourth and fifth carpometacarpal joints have a separate synovial membrane.
The movements permitted in the carpometacarpal articulations of the fingers are limited to slight gliding of the articular surfaces upon each other, the extent of which varies in the different joints.
This article was originally based on an entry from a public domain edition of Gray's Anatomy. As such, some of the information contained herein may be outdated. Please edit the article if this is the case, and feel free to remove this notice when it is no longer relevant.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Carpometacarpal_joint". A list of authors is available in Wikipedia.|