The trapezium bone (greater multangular bone) is a

carpal The carpal bones are the eight small bones that make up the wrist (or carpus) that connects the hand to the forearm. The term "carpus" is derived from the Latin carpus and the Greek καρπός (karpós), meaning "wrist". In human anatomy, th ...

bone in the

hand A hand is a prehensile, multi-fingered appendage located at the end of the forearm or forelimb of primates such as humans, chimpanzees, monkeys, and lemurs. A few other vertebrates such as the koala (which has two opposable thumbs on each "h ...

. It forms the

radial Radial is a geometric term of location which may refer to: Mathematics and Direction * Vector (geometric) In mathematics, physics, and engineering, a Euclidean vector or simply a vector (sometimes called a geometric vector or spatial vector) ...

border of the

carpal tunnel In the human body, the carpal tunnel or carpal canal is the passageway on the palmar side of the wrist that connects the forearm to the hand. The tunnel is bounded by the bones of the wrist and flexor retinaculum from connective tissue. Normall ...

Structure

The trapezium is distinguished by a deep groove on its anterior surface. It is situated at the radial side of the

carpus In human anatomy, the wrist is variously defined as (1) the carpus or carpal bones, the complex of eight bones forming the proximal skeletal segment of the hand; "The wrist contains eight bones, roughly aligned in two rows, known as the carpal ...

, between the

scaphoid The scaphoid bone is one of the carpal bones of the wrist. It is situated between the hand and forearm on the thumb side of the wrist (also called the lateral or radial side). It forms the radial border of the carpal tunnel. The scaphoid bone ...

and the first

metacarpal In human anatomy, the metacarpal bones or metacarpus form the intermediate part of the skeletal hand located between the phalanges of the fingers and the carpal bones of the wrist, which forms the connection to the forearm. The metacarpal bones ...

bone (the metacarpal bone of the thumb). It is homologous with the first distal carpal of reptiles and amphibians.

Surfaces

The trapezium is an irregular-shaped

carpal bone The carpal bones are the eight small bones that make up the wrist (or carpus) that connects the hand to the forearm. The term "carpus" is derived from the Latin wikt:carpus#Latin, carpus and the Greek language, Greek wikt:καρπός#Ancient Gre ...

found within the

. The trapezium is found within the distal row of carpal bones, and is directly adjacent to the

bone of the

thumb The thumb is the first digit of the hand, next to the index finger. When a person is standing in the medical anatomical position (where the palm is facing to the front), the thumb is the outermost digit. The Medical Latin English noun for thumb ...

. On its ulnar surface are found the

trapezoid A quadrilateral with at least one pair of parallel sides is called a trapezoid () in American and Canadian English. In British and other forms of English, it is called a trapezium (). A trapezoid is necessarily a Convex polygon, convex quadri ...

and

bones. The '' superior surface'' is directed upward and medialward; medially it is smooth, and articulates with the

; laterally it is rough and continuous with the lateral surface. The '' inferior surface'' is oval, concave from side to side, convex from before backward, so as to form a saddle-shaped surface for articulation with the base of the

first metacarpal bone The first metacarpal bone or the metacarpal bone of the thumb is the first bone proximal to the thumb. It is connected to the trapezium of the carpus at the first carpometacarpal joint and to the proximal thumb phalanx at the first metacarpophala ...

. This saddle-shaped articulation is partially responsible for the

's opposable motion. The ''dorsal surface'' is smooth. The ''palmar surface'' is narrow and rough. At its upper part is a deep groove, running from above obliquely downward and medialward; it transmits the tendon of the

Flexor carpi radialis In anatomy, flexor carpi radialis is a muscle of the human forearm that acts to flex and (radially) abduct the hand. The Latin ''carpus'' means wrist; hence flexor carpi is a flexor of the wrist. Origin and insertion The flexor carpi radialis is ...

, and is bounded laterally by an oblique ridge. This surface gives origin to the

Opponens pollicis The opponens pollicis is a small, triangular muscle in the hand, which functions to oppose the thumb. It is one of the three thenar muscles. It lies deep to the abductor pollicis brevis and lateral to the flexor pollicis brevis. Structure The opp ...

and to the Abductor and

Flexor pollicis brevis The flexor pollicis brevis is a muscle in the hand that flexes the thumb. It is one of three thenar muscles. It has both a superficial part and a deep part. Origin and insertion The muscle's superficial head arises from the distal edge of the fl ...

; it also affords attachment to the

transverse carpal ligament The flexor retinaculum (transverse carpal ligament, or anterior annular ligament) is a fibrous band on the palmar side of the hand near the wrist. It arches over the carpal bones of the hands, covering them and forming the carpal tunnel. Structur ...

. The ''lateral surface'' is broad and rough, for the attachment of ligaments. The ''medial surface'' presents two facets; the upper, large and concave, articulates with the

trapezoid bone The trapezoid bone (lesser multangular bone) is a carpal bone in tetrapods, including humans. It is the smallest bone in the distal row of carpal bones that give structure to the palm of the hand. It may be known by its wedge-shaped form, the bro ...

; the lower, small and oval, with the base of the

second metacarpal The second metacarpal bone (metacarpal bone of the index finger) is the longest, and its base the largest, of all the metacarpal bones.''Gray's Anatomy'' (1918). See infobox. Human anatomy Its base is prolonged upward and medialward, forming a ...

Tubercle of trapezium

The tubercle of trapezium is a

tubercle In anatomy, a tubercle (literally 'small tuber', Latin for 'lump') is any round nodule, small eminence, or warty outgrowth found on external or internal organs of a plant or an animal. In plants A tubercle is generally a wart-like projection ...

found on the anterior surface of the bone. It is where sometimes

abductor pollicis brevis muscle The abductor pollicis brevis is a muscle in the hand that functions as an abductor of the thumb. Structure The abductor pollicis brevis is a flat, thin muscle located just under the skin. It is a thenar muscle, and therefore contributes to the ...

attaches.

Function

The carpal bones function as a unit to provide a bony superstructure for the

. The trapezium is the most radial of the bones surrounding the

. It is important in thumb movement.

Clinical relevance

The trapezium is susceptible to arthritis at the joint with the

bone of the thumb, due to overuse.

History

The etymology derives from the Greek ''trapezion'' which means "a little table", from ''trapeza'' meaning "table", itself from ''(te)tra-'' "four" and ''pod-'' "foot". The bone was first documented in 1840.

Additional images

File:Trapezium bone (left) - animation01.gif, Position of trapezium (shown in red). Left hand. Animation. File:Trapezium bone (left) - animation02.gif, Trapezium of the left hand. File:Trapezium bone.jpg, Trapezium bone. File:RightHumanPosteriorDistalRadiusUlnaCarpals - Trapezium bone.png, Right hand posterior view (dorsal view). Thumb on bottom. File:RightHumanAnteriorDistalRadiusUlnaCarpals - Trapezium bone.png, Right hand anterior view (palmar view). Thumb on top. File:Gray219 - Trapezium bone.png, Bones of the left hand. Palmar surface. Trapezium shown in yellow. File:Gray220 - Trapezium bone.png, Bones of the left hand. Dorsal surface. Trapezium shown in yellow. File:Ospoignet - Trapezium.png, Cross section of wrist (thumb on left). Trapezium shown in red (labelled as "''Greater Multang''"). File:Gray422 - Trapezium.png, Transverse section across the wrist and digits. Trapezium is shown in yellow (labelled as "''Greater Multang''"). File:Gray334.png, Ligaments of wrist. Anterior view File:Gray416.png, Tendons of forefinger and vincula tendina.

References

{{DEFAULTSORT:Trapezium (Bone) Skeletal system Wrist Bones of the hand Carpal bones