Midcarpal joint | |
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Details | |
Identifiers | |
Latin | articulatio mediocarpalis |
TA98 | A03.5.11.102 |
TA2 | 1804 |
FMA | 35293 |
Anatomical terminology |
The midcarpal joint is formed by the scaphoid, lunate, and triquetral bones in the proximal row, and the trapezium, trapezoid, capitate, and hamate bones in the distal row. [1] The distal pole of the scaphoid articulates with two trapezial bones as a gliding type of joint. The proximal end of the scaphoid combines with the lunate and triquetrum to form a deep concavity that articulates with the convexity of the combined capitate and hamate in a form of diarthrodial, almost condyloid joint.
The cavity of the midcarpal joint is very extensive and irregular. The major portion of the cavity is located between the distal surfaces of the scaphoid, lunate, and triquetrum and proximal surfaces of the four bones of the distal row. Proximal prolongations of the cavity occur between the scaphoid and lunate and between the lunate and triquetrum. These extensions reach almost to the proximal surface of the bones in the proximal row and are separated from the cavity of the radiocarpal joint by the thin interosseous ligaments. There are three distal prolongations of the midcarpal joint cavity between the four bones of the distal row. The joint space between trapezium and trapezoid, or that between trapezoid and capitate, may communicate with cavities of the carpometacarpal joints, most commonly the second and third. The cavity between the first metacarpal and carpus is always separate from the midcarpal joint; the joint cavity between the hamate and fourth and fifth metacarpals is a separate cavity more often than not, but it may communicate normally with the midcarpal joint.
The wrist is perhaps the most complicated joint in the body. It permits movements in two planes - extension/flexion, ulnar deviation/radial deviation - and allows complex patterns of motion under significant strain.
Optimal wrist function requires stability of the carpal components in all joint positions under static and dynamic conditions.
Stability is achieved by a sophisticated geometry of articular surfaces and intricate system of ligaments, retinacula, and tendons, which also determine the relative motion of the carpal bones.
Ligamentous Apparatus of the Wrist
The carpal bones are not interlocked solely by their shapes; rather, they are held together by interosseous ligaments and by volar, dorsal, radial, and ulnar ligaments. The ligaments holding the carpal bones to each other, to the distal radius and ulna, and to the proximal ends of the metacarpals can be described as extrinsic, or capsular, and intrinsic, or interosseous (intercarpal). The function of the ligamentous system is guiding and constraining certain patterns of motion. Some portion of the ligaments are under tension in every position of the hand in relation to the forearm.
The carpal bones are the eight small bones that make up the wrist (carpus) that connects the hand to the forearm. The term "carpus" and "carpal" is derived from the Latin carpus and the Greek καρπός (karpós), meaning "wrist". In human anatomy, the main role of the carpal bones is to articulate with the radial and ulnar heads to form a highly mobile condyloid joint, to provide attachments for thenar and hypothenar muscles, and to form part of the rigid carpal tunnel which allows the median nerve and tendons of the anterior forearm muscles to be transmitted to the hand and fingers.
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; (2) the wrist joint or radiocarpal joint, the joint between the radius and the 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. This region also includes the carpal tunnel, the anatomical snuff box, bracelet lines, the flexor retinaculum, and the extensor retinaculum.
The trapezoid 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 broad end of the wedge constituting the dorsal, the narrow end the palmar surface; and by its having four articular facets touching each other, and separated by sharp edges. It is homologous with the "second distal carpal" of reptiles and amphibians.
The trapezium bone is a carpal bone in the hand. It forms the radial border of the carpal tunnel.
In human anatomy, the metacarpal bones or metacarpus, also known as the "palm bones", are the appendicular bones that form the intermediate part of the hand between the phalanges (fingers) and the carpal bones, which articulate with the forearm. The metacarpal bones are homologous to the metatarsal bones in the foot.
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. It forms the radial border of the carpal tunnel. The scaphoid bone is the largest bone of the proximal row of wrist bones, its long axis being from above downward, lateralward, and forward. It is approximately the size and shape of a medium cashew nut.
The capitate bone is a bone in the human wrist found in the center of the carpal bone region, located at the distal end of the radius and ulna bones. It articulates with the third metacarpal bone and forms the third carpometacarpal joint. The capitate bone is the largest of the carpal bones in the human hand. It presents, above, a rounded portion or head, which is received into the concavity formed by the scaphoid and lunate bones; a constricted portion or neck; and below this, the body. The bone is also found in many other mammals, and is homologous with the "third distal carpal" of reptiles and amphibians.
The hamate bone, or unciform bone, Latin os hamatum and occasionally abbreviated as just hamatum, is a bone in the human wrist readily distinguishable by its wedge shape and a hook-like process ("hamulus") projecting from its palmar surface.
The lunate bone is a carpal bone in the human hand. It is distinguished by its deep concavity and crescentic outline. It is situated in the center of the proximal row carpal bones, which lie between the ulna and radius and the hand. The lunate carpal bone is situated between the lateral scaphoid bone and medial triquetral bone.
The radius or radial bone is one of the two large bones of the forearm, the other being the ulna. It extends from the lateral side of the elbow to the thumb side of the wrist and runs parallel to the ulna. The ulna is longer than the radius, but the radius is thicker. The radius is a long bone, prism-shaped and slightly curved longitudinally.
The triquetral bone is located in the wrist on the medial side of the proximal row of the carpus between the lunate and pisiform bones. It is on the ulnar side of the hand, but does not directly articulate with the ulna. Instead, it is connected to and articulates with the ulna through the Triangular fibrocartilage disc and ligament, which forms part of the ulnocarpal joint capsule. It connects with the pisiform, hamate, and lunate bones. It is the 2nd most commonly fractured carpal bone.
The upper limbs or upper extremities are the forelimbs of an upright-postured tetrapod vertebrate, extending from the scapulae and clavicles down to and including the digits, including all the musculatures and ligaments involved with the shoulder, elbow, wrist and knuckle joints. In humans, each upper limb is divided into the shoulder, arm, elbow, forearm, wrist and hand, and is primarily used for climbing, lifting and manipulating objects. In anatomy, just as arm refers to the upper arm, leg refers to the lower leg.
Kienböck's disease is a disorder of the wrist. It is named for Dr. Robert Kienböck, a radiologist in Vienna, Austria who described osteomalacia of the lunate in 1910.
The carpometacarpal (CMC) joints are five joints in the wrist that articulate the distal row of carpal bones and the proximal bases of the five metacarpal bones.
The palmar radiocarpal ligament is a broad membranous band, attached above to the distal end of the radius, and passing downward to the scaphoid, lunate, triquetrum and capitate of the carpal bones in the wrist.
The intercarpal joints can be subdivided into three sets of joints : Those of the proximal row of carpal bones, those of the distal row of carpal bones, and those of the two rows with each other.
In the human body, the carpal tunnel or carpal canal is a flattened body cavity on the flexor (palmar/volar) side of the wrist, bounded by the carpal bones and flexor retinaculum. It forms the passageway that transmits the median nerve and the tendons of the extrinsic flexor muscles of the hand from the forearm to the hand. The median artery is an anatomical variant. When present it lies between the radial artery, and the ulnar artery and runs with the median nerve supplying the same structures innervated.
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 are often described as having "hands" instead of paws on their front limbs. The raccoon is usually described as having "hands" though opposable thumbs are lacking.
Wrist osteoarthritis is gradual loss of articular cartilage and hypertrophic bone changes (osteophytes). While in many joints this is part of normal aging (senescence), in the wrist osteoarthritis usually occurs over years to decades after scapholunate interosseous ligament rupture or an unhealed fracture of the scaphoid. Characteristic symptoms including pain, deformity and stiffness. Pain intensity and incapability are notably variable and do not correspond with arthritis severity on radiographs.
The muscles of the thumb are nine skeletal muscles located in the hand and forearm. The muscles allow for flexion, extension, adduction, abduction and opposition of the thumb. The muscles acting on the thumb can be divided into two groups: The extrinsic hand muscles, with their muscle bellies located in the forearm, and the intrinsic hand muscles, with their muscles bellies located in the hand proper.
This article incorporates text in the public domain from page 328 of the 20th edition of Gray's Anatomy (1918)