Carpal bones

Carpal bones . The carpus is made up of eight small bones in two transverse rows, one superior or antebrachial row and one row or metacarpal . The first comprises four bones: the scaphoid, the lunate, the pyramidal, and the pisiform. The second also includes four: the trapezoid, the trapezoid, the large and the hook bone.

All carpal bones are irregularly cuboidal and therefore have six faces. Of these 6 expensive faces , two, the anterior or palmar and the posterior or dorsal are rough and are related to the soft parts of the palmar and dorsal region. The other four, superior or brachial, inferior or metacarpal , external or radial and internal or ulnar, are smooth and covered with cartilage.

Summary

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  • 1 Scaphoid
    • 1 Articular faces
    • 2 Non-articular faces
  • 2 Half Moon
    • 1 Articular veneers
    • 2 Non-articular veneers
  • 3 Pyramid
    • 1 Articular veneers
    • 2 Non-articular veneers
    • 3 Pisiform
    • 4 Extremes
    • 5 Veneers
  • 4 Trapezium
    • 1 Articular veneers
  • 5 Non-articular veneers
  • 6 Trapezoid
    • 1 Articular veneers
    • 2 Non-articular veneers
  • 7 Large bone
  • 8 articular veneers
  • 9 Non-articular veneers
  • 10 Hook bone
  • 11 articular veneers
  • 12 Non-articular veneers
  • 13 Sources

Scaphoid

It is the most voluminous bone in the first row, which takes its name from its shape similar to a basket or skiff. Of the six faces of the scaphoid, three are articular and the other three are non-articular.

Joint faces

The three articular faces are: the upper, the lower and the internal. The upper, or better, the upper, external face is highly convex and articulates with the radius. The lower face, also convex, articulates with the first two bones of the second row, the trapezium and the trapezoid. The internal face is divided into two secondary faces by a small semicircular obtuse crest; the facet that is higher is flat and articulates with the lunate; the facet that is lower, much excavated, corresponds to the external part of the head of the large bone.

Non-articular faces

The three non-articular faces are the external, the anterior and the posterior. The external face is formed by a thick tubercle, which protrudes forward and out: it is the scaphoid tubercle, in which the external lateral ligament of the wrist joint comes to be inserted. The posterior or dorsal aspect is very narrow and is represented by a rough channel that runs obliquely down and out. The anterior or palmar face, narrow at the top, widens considerably at the bottom where it corresponds to the scaphoid tubercle .

The navicular is articulated with five bones

  • the radio
  • the semi-mole
  • the big bone
  • the trapezoid
  • the trapezoid.

Semilunar

Named because it has the shape of a crescent with the concavity facing downward, the crescent has four articular veneers for the immediate bones and two non-articular veneers.

Articular veneers

The four articular faces are: a top face, convex in shape, for the radius; a lower facet, concave from front to back (lunate face), for the head of the large bone and the upper extremity of the hook; an external face, flat and very small, for the scaphoid and an internal face, flat as well, but much larger, for the pyramid.

Non-articular veneers

Of the two non-articular veneers of the lunate, the anterior is convex and the posterior flat. Both are rough, but no muscle is inserted into them.

The lunate is articulated with five bones

  • the radio
  • the scaphoid
  • the pyramid
  • the hooky
  • the big bone

Pyramidal

The pyramid is shaped like a pyramid, the base of which faces up and out. Features four articular and two non-articular veneers

Articular veneers

The articular facets are a superior, convex and irregular facet, in relation to the triangular ligament of the inferior radioulnar joint; a lower, concave facet for the hook bone; a flat, external facet for the lunate; and a rounded antero-internal facet, for the pisiform, which is sometimes flat and other times slightly convex.

Non-articular veneers

The two non-articular veneers of the pyramid are the anterior and the posterior. The anterior or palmar face is narrow, rough and prolonged from top to bottom and from outside to inside. The posterior or dorsal face is very wide and has a transverse ridge, the crest of the pyramidal one, destined for ligament insertions. The crest of the pyramidal ends inside the pyramidal tubercle in which the posterior fascicle of the internal lateral ligament of the wrist joint is inserted. Above and below the ridge there are grooves with numerous vascular holes.

The pyramidal bone is articulated with four bones:

  • the ulna
  • the pisiform
  • the lunate
  • hook bone

Pisiform

Vertically elongated bone slightly flattened from the outside to the inside, with two ends and four faces

Extremes

The upper end, ordinarily the larger of the two, is directed upward and slightly outward. This limb does not exceed the level of the articular facet. The lower end extends more or less, in the form of a thick mamelon or pyramidal eminence, beyond the lower level of the facet. This end serves as an insertion to ligamentous fascicles that are inserted partly in the hook bone and partly in the fifth metacarpal

Veneers

The four faces of the pisiform, generally poorly determined, are divided into posterior, anterior, internal and external. The posterior aspect, in articular relation with the pyramidal bone, presents a small facet, rounded or oval, flat or slightly excavated. The internal face, convex and more or less rough, provides an insertion to the internal lateral ligament of the wrist joint. The external face presents most of the times a longitudinal channel that, very pronounced in the upper part of the one seen by its bone part, gradually lengthens as it approaches the lower end. This channel corresponds to the ulnar artery and the deep branch of the ulnar nerve. On the anterior side, the adductor of the little finger and the anterior ulnar are inserted.

The pisiform articulates only with the pyramidal bone

Trapeze

The trapezius, located between the scaphoid and the first metacarpal, has three articular faces and three non-articular faces.

Articular veneers

Articular veneers are a slightly concave, triangular upper veneer for the scaphoid; a lower facet, concave in the transverse direction and convex in the anteroposterior direction (saddle-shaped), for the upper extremity of the first metacarpal; an internal facet, concave at the top for the trapezoid, flat at the bottom for the external part of the second metacarpal; a small obtuse ridge, of transverse direction, indicates the limit of these two secondary faces.

Non-articular veneers

The anterior face is relatively narrow, especially in its internal part. In its external part, a deep channel is observed, destined for the passage of the palmaris major tendon. This canal is bounded on the outside by a strong linear process that runs obliquely forward and inward, called the trapezius tubercle. The back face is uneven, rough and with numerous holes. At its two ends, there are two small tubers intended for ligament insertions. The external face is quadrilateral and rough, and also lends insertion to ligaments.

The trapezium is articulated with four bones:

  • the scaphoid
  • the trapezoid
  • the first metacarpal
  • the second metacarpal.

Trapezoid

The trapezoid is located between four bones, the scaphoid at the top, the second metacarpal at the bottom, the trapezius on the outside and the large bone on the inside, therefore presenting four articular faces. In addition, it has two non-articular veneers

Articular veneers

Triangular and slightly concave upper facet for articulation with the navicular; Lower facet convex in the transverse direction and markedly prolonged from front to back for articulation with the second metacarpal; for the trapezoid, it has an external face, convex; for the large bone, finally, an irregularly flat internal veneer

Non-articular veneers

The anterior or palmar aspect, corresponding to the palm of the hand, and the posterior or dorsal aspect. Both are rough, and the ridge is also much more extensive than the palmar

The trapezoid articulates with four bones

  • above, with the scaphoid;
  • below, with the second metacarpal
  • outside, with the trapezoid
  • inside, with the big bone

Big bone

The large bone is the most voluminous of all the carpal bones. It is made up of three parts: a superior, rounded part, the head; a lower portion, very bulky, the body, and another middle portion, more or less narrow, the neck. Also features articular veneers and non-articular veneers

Articular veneers

In all its perimeter it articulates with the immediate bones, having the following veneers: on its upper face, a convex and semilunar articular veneer; on its external face, a first, convex facet, located upwards, for the concavity of the scaphoid and a second, smaller, flat facet, located downwards, for the trapezoid; on its internal face, an extensive facet, to which a smaller one is frequently added, for the articulation of this face with the hook bone; on its lower face, three contiguous veneers, but separated by generally very visible ridges, for the second, third, and fourth metacarpals; of these three metacarpal veneers, the middle veneer, destined for the third metacarpal, is wide and triangular, with a posterior base; the external facet, intended for the second metacarpal, is narrow and prolonged from front to back; finally, the internal veneer, destined for the fourth metacarpal, is very small and is limited to the posterior part of the bone.

Non-articular veneers

The non-articular veneers also occupy the palmar aspect and the dorsal aspect of the bone here. These two veneers have a transverse channel above the neck, and below this channel, a rough surface in which there are numerous vascular holes . Finally, in the posterior and external part of the large bone is the process of the large bone, which leads obliquely towards the fourth metacarpal articulating with the

The large bone is articulated with seven bones

  • the scaphoid
  • the lunate
  • the trapezoid
  • hook bone
  • the three central metacarpals

Hook bone

The hook bone is the last bone in the second row of the carpus. Much wider at the bottom than at the top, it looks rather like a pyramid, the base of which is in relation to the last two metacarpals.

Articular veneers

These articular veneers occupy the entire circumference of the bone. The underside or base has two juxtaposed articular faces, both concave. The external one is in relation to the fourth metacarpal; the internal one, with the fifth. These two veneers together are shaped like a saddle. The upper limb or vertex is shaped like an obtuse edge directed from front to back; on this the moon is placed. On each side of this edge and gaining the lateral faces of the bone, two articular facets extend one internal, very oblique, that looks up and in, for the pyramidal, and another vertical external, that looks out, for the large bone .

Non-articular veneers

They are the anterior and posterior faces. The dorsal face is very broad, rough, strewn with holes. From the anterior face or palm a long process is born, the uncinate process. This transversely flattened process curves like a hook. Of these two faces, the external one is part of the carpal canal and the internal one has a caru that extends over the inferior border and through which the cubitopalma artery runs. The apex of the uncinate process, rounded and obtuse, gives insertion to the anterior ligament of the carpus

The hook bone is articulated with five bones

  • the pyramid
  • the big bone
  • the lunate
  • the last two metacarpals.

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