Wrist extensor compartments (numbered).PNG

In human anatomy, the wrist is variously defined as (1) the Carpal bones, 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 bones." (2) the wrist joint or radiocarpal joint, the joint between the radius (bone), radius and the Carpal bones, carpus and; (3) the anatomical region surrounding the carpus including the distal parts of the bones of the forearm and the proximal parts of the metacarpus or five metacarpal bones and the series of joints between these bones, thus referred to as ''wrist joints''. "With the large number of bones composing the wrist (ulna, radius, eight carpas, and five metacarpals), it makes sense that there are many, many joints that make up the structure known as the wrist." This region also includes the carpal tunnel, the anatomical snuff box, bracelet lines, the Flexor retinaculum of the hand, flexor retinaculum, and the extensor retinaculum of the hand, extensor retinaculum.

As a consequence of these various definitions, fractures to the carpal bones are referred to as carpal fractures, while fractures such as distal radius fracture are often considered fractures to the wrist.

Structure

The distal radioulnar articulation, distal radioulnar joint is a pivot joint located between the bones of the forearm, the Radius (bone), radius and ulna. Formed by the head of ulna, head of the ulna and the ulnar notch of the radius, this joint is separated from the radiocarpal joint by an articular disk lying between the radius and the ulnar styloid process, styloid process of the ulna. The capsule of the joint is lax and extends from the Sacciform recess of distal radioulnar joint, inferior sacciform recess to the ulnar shaft. Together with the proximal radioulnar joint, the distal radioulnar joint permits pronation and supination.

The radiocarpal joint or wrist joint is an condyloid joint, ellipsoid joint formed by the radius and the articular disc proximally and the proximal row of carpal bones distally. The carpal bones on the ulnar side only make intermittent contact with the proximal side — the triquetrum only makes contact during ulnar abduction. The capsule, lax and un-branched, is thin on the dorsal side and can contain synovial folds. The capsule is continuous with the midcarpal joint and strengthened by numerous ligaments, including the palmar radiocarpal ligament, palmar and dorsal radiocarpal ligaments, and the ulnar collateral ligament (wrist), ulnar and Radial collateral ligament (wrist), radial collateral ligaments.

The parts forming the radiocarpal joint are the lower end of the radius (bone), radius and under surface of the articular disk above; and the scaphoid, Lunate bone, lunate, and triquetral bones below. The articular surface of the radius and the undersurface of the articular disk form together with a transversely elliptical concave surface, the receiving cavity. The superior articular surfaces of the scaphoid, lunate, and triquetrum form a smooth convex surface, the Condyle (anatomy), condyle, which is received into the concavity.

Carpal bones of the hand:
* ''Proximal:'' A=Scaphoid bone, Scaphoid, B=Lunate bone, Lunate, C=Triquetrum bone, Triquetrum, D=Pisiform bone, Pisiform
* ''Distal:'' E=Trapezium bone, Trapezium, F=Trapezoid bone, Trapezoid, G=Capitate bone, Capitate, H=Hamate bone, Hamate

In the hand proper a total of 13 bones form part of the wrist: eight carpal bones—scaphoid, lunate bone, lunate, triquetral, pisiform, trapezium (bone), trapezium, trapezoid bone, trapezoid, capitate, and hamate— and five Metacarpus, metacarpal bones—the First metacarpal bone, first, Second metacarpal bone, second, Third metacarpal bone, third, fourth metacarpal bone, fourth, and fifth metacarpal bones.

The midcarpal joint is the S-shaped joint space separating the proximal and distal rows of carpal bones. The Intercarpal articulations, intercarpal joints, between the bones of each row, are strengthened by the radiate carpal ligament, radiate carpal and pisohamate ligaments and the Palmar intercarpal ligaments, palmar, Interosseous intercarpal ligaments, interosseous, and dorsal intercarpal ligaments. Some degree of mobility is possible between the bones of the proximal row while the bones of the distal row are connected to each other and to the metacarpal bones —at the carpometacarpal joints— by strong ligaments —the pisometacarpal ligament, pisometacarpal and Palmar carpometacarpal ligament, palmar and dorsal carpometacarpal ligament— that makes a functional entity of these bones. Additionally, the joints between the bases of the metacarpal bones —the intermetacarpal articulations— are strengthened by Dorsal intermetacarpal ligament, dorsal, Interosseous intermetacarpal ligament, interosseous, and palmar intermetacarpal ligaments.

The earliest carpal bones to ossify are capitate bone and hamate bone in the first six months of an infant life.

Articulations

The radiocarpal, intercarpal, midcarpal, carpometacarpal, and intermetacarpal joints often intercommunicate through a common synovial cavity.

Articular Surfaces

It has two articular surfaces named, proximal and distal articular surfaces respectively. The proximal articular surface is made up of the lower end of the radius and a triangular articular disc of the inferior radio-ulnar joint. On the other hand, the distal articular surface is made up of proximal surfaces of the scaphoid, triquetral and lunate bones.

Function

Movement

The extrinsic hand muscles are located in the forearm where their bellies form the proximal fleshy roundness. When contracted, most of the tendons of these muscles are prevented from standing up like taut bowstrings around the wrist by passing under the flexor retinaculum of the hand, flexor retinaculum on the palmar side and the extensor retinaculum of the hand, extensor retinaculum on the dorsal side. On the palmar side the carpal bones form the carpal tunnel, through which some of the flexor tendons pass in tendon sheaths that enable them to slide back and forth through the narrow passageway (see carpal tunnel syndrome).

Starting from the mid-position of the hand, the Anatomical terms of location#Relative motions, movements permitted in the wrist proper are (muscles in order of importance):

* Marginal movements: radial deviation (abduction, movement towards the thumb) and ulnar deviation (adduction, movement towards the little finger). These movements take place about a dorsopalmar axis (back to front) at the radiocarpal and midcarpal joints passing through the capitate bone.
** Radial abduction (up to 20°): Extensor carpi radialis longus muscle, extensor carpi radialis longus, Abductor pollicis longus muscle, abductor pollicis longus, Extensor pollicis longus muscle, extensor pollicis longus, Flexor carpi radialis muscle, flexor carpi radialis, Flexor pollicis longus muscle, flexor pollicis longus
** Ulnar adduction (up to 30°): Extensor carpi ulnaris muscle, extensor carpi ulnaris, Flexor carpi ulnaris muscle, flexor carpi ulnaris, Extensor digitorum muscle, extensor digitorum, Extensor digiti minimi muscle, extensor digiti minimi
* Movements in the plane of the hand: flexion (palmar flexion, tilting towards the palm) and extension (dorsiflexion, tilting towards the back of the hand). These movements take place through a transverse axis passing through the capitate bone. Palmar flexion is the most powerful of these movements because the flexors, especially the finger flexors, are considerably stronger than the extensors.

* Extension (up to 60°): Extensor digitorum muscle, extensor digitorum, Extensor carpi radialis longus muscle, extensor carpi radialis longus, Extensor carpi radialis brevis muscle, extensor carpi radialis brevis, Extensor indicis muscle, extensor indicis, Extensor pollicis longus muscle, extensor pollicis longus, Extensor digiti minimi muscle, extensor digiti minimi, extensor carpi ulnaris
* Palmar flexion (up to 70°): Flexor digitorum superficialis muscle, flexor digitorum superficialis, Flexor digitorum profundus muscle, flexor digitorum profundus, Flexor carpi ulnaris muscle, flexor carpi ulnaris, Flexor pollicis longus muscle, flexor pollicis longus, Flexor carpi radialis muscle, flexor carpi radialis, Abductor pollicis longus muscle, abductor pollicis longus
* Intermediate or combined movements

However, movements at the wrist can not be properly described without including movements in the distal radioulnar joint in which the rotary actions of supination and pronation occur and this joint is therefore normally regarded as part of the wrist.

Clinical significance

Wrist pain has a number of causes, including carpal tunnel syndrome, ganglion cyst, Tendinopathy, tendinitis, and Wrist osteoarthritis, osteoarthritis. Tests such as Phalen's test involve palmarflexion at the wrist.

The hand may deviate at the wrist in some conditions, such as rheumatoid arthritis.

Ossification of the bones around the wrist is one indicator used in taking a Bone age#Methods, bone age.

A ''wrist fracture'' usually means a fracture of the Distal radius fracture, distal radius.

History

Etymology

The English language, English word "wikt:wrist, wrist" is Etymology, etymologically derived from the ancient German language, German word ''wristiz'' from which are derived modern German '':de:rist, rist'' ("wikt:instep, instep", "wrist") and modern Swedish language, Swedish ''wikt:vrist, vrist'' ("instep", "wikt:ankle, ankle"). The base ''writh-'' and its variants are associated with Old English words "wikt:wreath, wreath", "wikt:wrest, wrest", and "wikt:writhe, writhe". The ''wr-'' sound of this base seems originally to have been symbolic of the action of twisting.

See also

* Brunelli procedure, related to instability in the wrist, caused by a torn scapholunate ligament.
* Knuckle-walking, a kind of quadrupedal locomotion involving wrist bone specialization
* Wristlocks use movement extremes of the wrist for martial applications.
* Glossary of bowling#Wrist, Glossary of bowling § Wrist, a measure of wrist position in bowling ball deliveries

Additional images

File:Dissection of the human hand - 02.jpg, Wrist joint. Deep dissection. Posterior view.
File:Slide5kaka.JPG, Wrist joint. Deep dissection. Posterior view.
File:Slide2dsds.JPG, Wrist joint. Deep dissection.Anterior, palmar, view.
File:Slide3dsds.JPG, Wrist joint. Deep dissection.Anterior, palmar, view.

References

Sources

*
*

External links

*

{{Authority control

Wrist,
Joints, *Wrist
Upper limb anatomy