| Metacarpal bones | |
|---|---|
_01_palmar_view_with_label.png) Metacarpals shown in red. Left hand, anterior (palmar) view. | |
 The five metacarpal bones, numbered. Left hand, anterior (palmar) view. os primum metacarpale / os metacarpale I os secundum metacarpale / os metacarpale II os tertium metacarpale / os metacarpale III os quartum metacarpale / os metacarpale IV os quintum metacarpale / os metacarpale V | |
| Details | |
| Origins | Carpal bones ofwrist |
| Insertions | Proximalphalanges |
| Articulations | Carpometacarpal,intermetacarpal,metacarpophalangeal |
| Identifiers | |
| Latin | os metacarpale pl. ossa metacarpalia |
| MeSH | D050279 |
| TA98 | A02.4.09.001 |
| TA2 | 1264 |
| FMA | 9612 |
| Anatomical terms of bone | |
Inhuman anatomy, themetacarpal bones ormetacarpus, also known as the "palm bones", are theappendicularbones that form the intermediate part of thehand between thephalanges (fingers) and thecarpal bones (wrist bones), whicharticulate with theforearm. The metacarpal bones arehomologous to themetatarsal bones in thefoot.
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The metacarpals form a transverse arch to which the rigid row of distal carpal bones are fixed. The peripheral metacarpals (those of the thumb and little finger) form the sides of the cup of the palmar gutter and as they are brought together they deepen this concavity. The index metacarpal is the most firmly fixed, while the thumb metacarpal articulates with the trapezium and acts independently from the others. The middle metacarpals are tightly united to the carpus by intrinsic interlocking bone elements at their bases. The ring metacarpal is somewhat more mobile while the fifth metacarpal is semi-independent.[1]
Each metacarpal bone consists of a body or shaft, and two extremities; thehead at the distal or digital end (near the fingers), and thebase at the proximal or carpal end (close to the wrist).
Thebody (shaft) isprismoid in form, and curved, so as to be convex in the longitudinal direction behind, concave in front. It presents three surfaces: medial, lateral, and dorsal.
Thebase (basis) orcarpal extremity is of a cuboidal form, and broader behind than in front. It articulates with thecarpal bones and with the adjoining metacarpal bones while its dorsal and volar surfaces are rough, for the attachment ofligaments.[2]
Thehead (caput) ordigital extremity presents an oblong surface markedly convex from before backward, less so transversely, and flattened from side to side; it articulates with theproximal phalanx. It is broader, and extends farther upward, on the volar than on the dorsal aspect, and is longer in the antero-posterior than in the transverse diameter. On either side of the head is a tubercle for the attachment of the collateral ligament of themetacarpophalangeal joint.
The dorsal surface, broad and flat, supports the tendons of theextensor muscles.
The volar surface is grooved in the middle line for the passage of the flexor tendons, and marked on either side by an articular eminence continuous with the terminal articular surface.[2]
The neck, orsubcapital segment, is the transition zone between the body and the head.
Besides themetacarpophalangeal joints, the metacarpal bonesarticulate bycarpometacarpal joints as follows:
Extensor Carpi Radialis Longus/Brevis: Both insert on the base of metacarpal II; Assist with wrist extension and radial flexion of the wrist
Extensor Carpi Ulnaris: Inserts on the base of metacarpal V; Extends and fixes wrist when digits are being flexed; assists with ulnar flexion of wrist
Abductor Pollicis Longus: Inserts on the trapezium and base of metacarpal I; Abducts thumb in frontal plane; extends thumb at carpometacarpal joint
Opponens Pollicis: Inserts on metacarpal I; flexes metacarpal I to oppose the thumb to the fingertips
Opponens digiti minimi: Inserts on the medial surface of metacarpal V; Flexes metacarpal V at carpometacarpal joint when little finger is moved into opposition with tip of thumb; deepens palm of hand.[3]
The fourth and fifth metacarpal bones are commonly "blunted" or shortened, inpseudohypoparathyroidism andpseudopseudohypoparathyroidism.
A blunted fourth metacarpal, with normal fifth metacarpal, can signifyTurner syndrome.
Blunted metacarpals (particularly the fourth metacarpal) are a symptom ofnevoid basal-cell carcinoma syndrome.
The neck of a metacarpal is a common location for aboxer's fracture, but all parts of the metacarpal bone (including head, body and base) are susceptible to fracture. During their lifetime, 2.5% of individuals will experience at least one metacarpal fracture.Bennett's fracture (base of the thumb) is the most common.[4] Several types of treatment exist ranging from non-operative techniques, with or without immobilization, to operative techniques using closed oropen reduction and internal fixation (ORIF). Generally, most fractures showing little or no displacement can be treated successfully without surgery.[5] Intraarticular fracture-dislocations of the metacarpal head or base may require surgical fixation, as fragment displacement affecting the joint surface is rarely tolerated well.[5]
In four-legged animals, the metacarpals form part of the forefeet, and are frequently reduced in number, appropriate to the number of toes. Indigitigrade andunguligrade animals, the metacarpals are greatly extended and strengthened, forming an additional segment to the limb, a feature that typically enhances the animal's speed. In bothbirds andbats, the metacarpals form part of the wing.
The GreekphysicianGalen used to refer to themetacarpus as μετακάρπιον.[6][7] The Latin formmetacarpium[6][8][9][10] more truly resembles[6] its Ancient Greek predecessor μετακάρπιον than metacarpus.[11][12]Meta– is Greek for beyond and carpal from Ancient Greekκαρπός (karpós, “wrist”).In anatomic Latin, adjectives likemetacarpius,[13]metacarpicus,[14]metacarpiaeus,[15]metacarpeus,[16]metacarpianus[17] andmetacarpalis[12] can be found. The formmetacarpius is more true[9][13] to the later Greek form μετακάρπιος.[13]Metacarpalis, as inossa metacarpalia in the current official Latin nomenclature,Terminologia Anatomica[12] is a compound consisting of Latin and Greek parts.[14] The usage of such hybrids in anatomic Latin is disapproved by some.[9][14]
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This article incorporates text in thepublic domain frompage 227 of the 20th edition ofGray's Anatomy(1918)
