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Wrist Bones by A.Griguolo

Generality

The bones of the wrist are the bony elements used to constitute the important articulation located between the forearm and the hand (articulation of the wrist).

The bones of the wrist include the 8 bones of the carpus (proximal bones of the skeleton of the hand) and the final ends of the ulna and radius (bones of the forearm).

Short review of what is the Wrist?

Pulse is the term that, in human anatomy, indicates:

  • The even region of the body that marks the end of the forearm and the beginning of the hand, e
  • The joint that joins the forearm to the hand.

What are the Bones of the Wrist?

The bones of the wrist are the bone grouping that gives life to the even region of the human body placed at the border between the forearm and the hand, and which contributes in a decisive way to the constitution of the joint present in the aforementioned region ( articulation of the wrist ).

Anatomy

According to most human anatomy manuals, the bones of the wrist are the 8 bones of the carpus (or carpal bones) and the bones of the ulna and radius forearm, with their respective distal epiphyses .

Brief review of the proximal-distal terms

" Proximal " means "closer to the center of the body" or "closer to the point of origin"; " distal ", instead, means "farther from the center of the body" or "farther from the point of origin.

Examples:

  • The femur is proximal to the tibia, which is distal to the femur.
  • In the femur, the extremity bordering the trunk is the proximal end, while the extremity bordering the knee is the distal end.

The 8 bones of the carpus are the scaphoid, the lunate, the triquatum, the pisiform, the trapezoid, the trapezoid, the capitate and the uncinate .

From the irregular shape (irregular bones ), these bony elements together constitute the proximal portion of the skeleton of the hand.

Including between the metacarpals (group of bones constituting the intermediate portion of the skeleton of the hand) and the bones of the forearm, the carpal bones are arranged equally on two rows: a row near ulna and radius, called proximal row and including scaphoid, semilunare, triquetro and pisiforme, and a row behind the 5 metacarpal bones, called distal row and composed of trapezoid, trapezoid, capitate and hooked.

NEXT ROW

Observing the skeleton of a hand from the side of the palm, it is possible to note that the latero-medial disposition (that is from the outside towards the inside) of the carpal bones of the proximal row is: scaphoid, semilunar, triqueter and pisiform.

  • Scafoide: it is one of the two carpal bones that come into direct contact with the distal end of the radius; moreover, it houses part of the distal (or carpal) end of three ligaments of the wrist - the radial collateral, the palmar radiocarpal and the dorsal radiocarpal - as well as one of the two radial (or lateral) ends of the transverse carpal ligament, ie the band of tissue fibrous connective tissue constituting the carpal tunnel .

    As a wrist bone, it borders: the radio, proximally; semi-lunar and happened, medially; trapezoid and trapezoid distally.

  • Semilunare: it is the other of the two bones of the carpus that join directly in the distal end of the radium; in addition, it houses part of the distal (or carpal) end of two ligaments of the wrist, the palmar radiocarpal and the dorsal radiocarpal.

    As a wrist bone, it borders: the radio, proximally; scaphoid, laterally; triquetro, medially; happened, distally.

  • Triqueter: it is the bone of the carpus that looks at the distal end of the ulna, without however entering it in direct contact; moreover, it offers attachment to part of the distal (or carpal) end of three ligaments of the wrist: the ulnar collateral, the palmar radiocarpal and the dorsal radiocarpal.

    As a wrist bone, it borders on: the so-called articular disc of the wrist, proximally; the lunate, laterally; the pisiform, medially; the hamate, distally.

  • Pisiform: it is one of the two bones of the carpus on which one of the two ulnar (or medial) extremities of the transverse carpal ligament is attached; moreover, it is an insertion site for part of the distal (or carpal) end of the ligament of the ulnar collateral wrist.

    As a wrist bone, it borders only on the tris, laterally.

Brief review of the medial-lateral terms

Recalling that the sagittal plane is the anteroposterior division of the human body from which two equal and symmetrical halves are derived, " medial " means "near" or "closer" to the sagittal plane, while " lateral " means "far" or " farther "from the sagittal plane.

Examples:

  • The second toe is lateral to the big toe, but is medial to the third toe.
  • The tibia is medial to the fibula, which is lateral to the tibia.

DISTAL ROW

Still observing the skeleton of a hand from the palm side, it is possible to ascertain that the latero-medial arrangement of the carpal bones of the distal row is: trapezoid, trapezoid, capitate and hooked.

  • Trapezoid: it is the second bone of the carpus (after the scaphoid) on which the other radial end of the transverse carpal ligament (carpal tunnel ligament) finds insertion; in addition, it houses part of the distal (or carpal) end of the radial collateral ligament.

    As a wrist bone, it borders on: the scaphoid, proximally; the trapeze, medially; the first and second metacarpals, distally.

  • Trapezoid: it is the smallest bone in the distal row of the carpus.

    As a wrist bone, it borders on: the scaphoid, proximally; trapeze, laterally; happened, medially; the second metacarpal, distally.

  • Capitato: it is the central bone of the carpus, on which it finds insertion, sometimes, part of the distal (or carpal) end of the palmar radiocarpal ligament.

    Like wrist bone, it borders: the scaphoid and the lunate, proximally; the trapezoid, laterally; the hamato, medially; a part of the second, the third and fourth metacarpal.

  • Uncinato: it is the second bone of the carpus (after the pisiform) on which the other ulnar end of the transverse carpal ligament is inserted.

    As a wrist bone, it borders on: the triqueter and the lunate proximally; the capitate, laterally; the fourth and fifth metacarpal, distally.

Radio and Distal Epiphysis of the Radio

Assuming that the upper limb is extended along the body and with the palm facing towards the observer, the radium is the lateral bone of the forearm.

Radium is a long bone, therefore it is developed in length and is characterized by:

  • A narrow central portion, which takes the name of body or diaphysis ;
  • Two bulky ends, called proximal epiphysis and distal epiphysis .

Located on the opposite side to the proximal epiphysis, the distal epiphysis of the radius is the end of the bone in question closest to the hand and the bones of the carpus.

The distal epiphyses of the radius invest in the role of the wrist bone:

  • The two facet joints, present on the bony surface that looks towards the carpus and hand, and deputed to join the scaphoid, one, and the lunate, the other;

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  • The areas hosting the proximal (or radial ) end of three ligaments of the wrist : the radial collateral, the palmar radiocarpal and the dorsal radiocarpal.

Did you know that ...

The distal end of the radium enters into relationship with the scaphoid through the articular facet placed in a more lateral position (lateral articular facet), while it articulates with the semilunar through the articular facet located in a more medial position (medial articular facet).

Ulna and Distal End of the Ulna

Always assuming that the upper limb is extended along the body and with the palm of the hand facing the observer, the ulna is the medial bone of the forearm.

Like radium, the ulna belongs to the category of long bones, therefore three portions are recognizable on it: the proximal end, the diaphysis and the distal end.

Located on the side opposite the proximal epiphysis, the distal epiphysis of the ulna is the end of the bone in question closest to the hand and the carpus bone group.

To make the distal epiphysis of the ulna a bone of the wrist is the bone projection present on the inferior margin, in medial position, since on this the proximal (or ulnar) end of the ulnar collateral ligament is attached.

Did you know that ...

  • The bone projection of the distal epiphysis of the ulna, which houses the proximal end of the ulnar collateral ligament, is called the styloid process ;
  • Between the distal end of the ulna and the carpus bones (to be precise, the trisum) there is a fibrocartilaginous structure, called the articular disk of the wrist, whose purpose is to act as an anti-friction pad.

    Function aside, the presence of the articular disc of the wrist is important, because it prevents direct contact between the distal extremity of the ulna and the carpus (NB: the latter is only the aforementioned ulnar collateral ligament).

Function

The wrist bones have the important task of forming the wrist joint. This articulation is fundamental for the functionality of the hand; in fact, it allows the movements of:

  • Hand bending . It is the movement that allows you to bring the palm of your hand closer to your arm. Imagining to observe an upper limb completely extended forward, the flexion of the wrist is the movement that bends the hand downwards.
  • Hand extension . It is the movement that allows the back of the hand to be brought closer to the arm. Imagining to observe an upper limb completely extended forward, the extension of the wrist is the movement that bends the hand upwards.
  • Radial deviation of the hand . It is the movement that allows the side of the hand to be brought closer with the thumb to the radio.
  • Ulnar deviation of the hand . It is the movement that allows the side of the hand to be approached with the little finger to the ulna.
  • Hand surround . It is the rotation movement of the hand.

diseases

Like all bones in the human body, wrist bones can also be subject to fractures.

In most cases, at the origin of a fracture of the wrist bones there is a traumatic event (eg: violent impact of the hand with the ground, after an accidental fall); more rarely, there is the continuous repetition of a movement of the hand harmful to the integrity of the carpus or of the distal extremities of ulna and radius (example of stress fracture to the wrist bones).

Traumatic fractures of the wrist bones are more serious, from a clinical point of view, than stress fractures.