THE HAND
BONES OF THE LOWER ROW
The Trapezium is of very irregular form. It may be distinguished by a deep groove, for the tendon of the Flexor carpi radialis muscle. It is situated at the external and inferior part of the carpus, between the scaphoid and first meta-carpal bone. The superior surface, concave and smooth, is directed upwards and inwards, and articulates with the scaphoid. Its inferior surface, directed downwards and outwards, is oval, concave from side to side, convex from before backwards, so as to form a saddle-shaped surface, for articulation with the base of the first metacarpal bone. The anterior or palmar surface is narrow and rough. At its upper part is a deep groove, running from above obliquely downwards and inwards; it transmits the tendon of the Flexor carpi radialis, and is bounded externally by a prominent ridge, the oblique ridge of the trapezium. This surface gives attachment to the Abductor pollicis, Flexor ossis metacarpi, and Flexor brevis pollicis muscles; and the anterior annular ligament. The posterior or dorsal surface is rough, and the external surface also broad and rough, for the attachment of ligaments. The internal surface presents two articular facets; the upper one, large and concave, articulates with the trapezoid; the lower one, narrow and flattened, with the base of the second metacarpal bone.
To ascertain to which hand it belongs, hold the bone with the grooved palmar surface upwards, and the external, broad, non-articular surface backwards; the saddle-shaped surface will then be directed to the side to which the bone belongs.
Articulations. With four bones: the scaphoid above, the trapezoid and second metacarpal bones internally, the first metacarpal below.
Attachment of Muscles. Abductor pollicis, Flexor ossis metacarpi, part of the Flexor brevis pollicis, and the anterior annular ligament.
Bones of the Left Hand
The Trapezoid is the smallest bone in the second row. It may be known by its wedge-shaped form; its broad end occupying the dorsal, its narrow end the palmar surface of the hand. Its superior surface, quadrilateral in form, smooth and slightly concave, articulates with the scaphoid. The inferior surface articulates with the upper end of the second metacarpal bone; it is convex from side to side, concave from before backwards, and subdivided, by an elevated ridge, into two unequal lateral facets. The posterior or dorsal, and anterior or palmar surfaces are rough, for the attachment of ligaments; the former being the larger of the two. The external surface, convex and smooth, articulates with the trapezium. The internal surface is concave and smooth below, for articulationwith the os magnum, rough above, for the attachment of an interosseous ligament. To ascertain to which side this bone belongs, let the broad dorsal surface be held upwards, and its inferior concavo-convex surface forwards; the internal concave surface will then point to the side to which the bone belongs.
Articulations. With four bones; the scaphoid above, second metacarpal bone below, trapezium externally, os magnum internally.
Attachment of Muscles. Part of the Flexor brevis pollicis.
The Os Magnum is the largest bone of the carpus, and occupies the centre of the wrist. It presents, above, a rounded portion or head, which is received into the concavity formed by the scaphoid and semi-lunar bones; a constricted portion or neck; and, below, the body. Its superior surface ib rounded, smooth, and articulates with the semi-lunar. Its inferior surface is divided, by two ridges, into three facets, for articulation with the second, third, and fourth metacarpal bones; that for the third (the middle facet) being the largest of the three. The posterior or dorsal surface is broad and rough, and the anterior or palmar narrow, rounded, but also rough, for the attachment of ligaments. The external surface articulates with the trapezoid by a small facet at its anterior inferior angle, behind which is a rough depression, for the attachment of an interosseous ligament. Above this is a deep and rough groove, which forms part of the neck, and serves for the attachment of ligaments, bounded superiorly by a smooth, convex surface, for articulation with the scaphoid. The internal surface articulates with the unciform by a smooth, concave, oblong facet, which occupies its posterior and superior parts; rough in front, for the attachment of an interosseous ligament.
To ascertain to which hand this bone belongs, the rounded head should be held upwards, and the broad dorsal surface forwards; the internal concave articular surface will point to its appropriate side.
Articulations. With seven bones: the scaphoid and semi-lunar above; the second, third, and fourth metacarpal below; the trapezoid on the radial side; and the unciform on the ulnar side.
Attachment of Muscles. Part of the Flexor brevis pollicis.
The Unciform bone may be readily distinguished by its wedge-shaped form, and the hook-like process that projects from its palmar surface. It is situated at the inner and lower angle of the carpus, with its base downwards, resting on the two inner metacarpal bones, and its apex directed upwards and outwards. Its superior surface, the apex of the wedge, is narrow, convex, smooth, and articulates with the semi-lunar. Its inferior surface articulates with the fourth and fifth metacarpal bones, the concave surface for each being separated by a ridge, which runs from before backwards. The posterior or dorsal surface is triangular and rough, for ligamentous attachment. The anterior or palmar surface presents at its lower and inner side a curved, hook-like process of bone the unciform process, directed from the palmar surface forwards and outwards. It gives attachment, by its apex, to the annular ligament; by its inner surface, to the Flexor brevis minimi digiti, and the Flexor ossis metacarpi minimi digiti; and is grooved on its outer side, for the passage of the Flexor tendons into the palm of the hand. This is one of the four eminences on the front of the carpus, to which the anterior annular ligament is attached; the others being the pisiform internally ; the oblique ridge of the trapezium and the tuberosity of the scaphoid externally. The internal surface articulates with the cuneiform by an oblong surface, cut obliquely from above downwards and inwards. Its external surface articulates with the os magnum by its upper and posterior part, the remaining portion being rough, for the attachment of ligaments.
To ascertain to which hand it belongs, hold the apex of the bone upwards, and the broad dorsal surface backwards; the concavity of the unciform process will be directed to the side to which the bone belongs.
Articulations. With five bones: the semi-lunar above, the fourth and fifth metacarpal below, the cuneiform internally, the os magnum externally.
Attachment of Muscles. To two: the Flexor brevis minimi digiti, the Flexor ossis metacarpi minimi digiti; and to the anterior annular ligament.
THE METACARPUS
The Metacarpal bones are five in number; they are long cylindrical bones, presenting for examination a shaft and two extremities.
COMMON CHARACTERS OF THE METACARPAL BONES
The shaft is prismoid in form, and curved longitudinally, so as to be convex in the longitudinal direction behind, concave in front. It presents three surfaces; two lateral, and one posterior. The lateral surfaces are concave, for the attachment of the Interossei muscles, and separated from one another by a prominent line. The posterior or dorsal surface is triangular, smooth, and flattened below, and covered, in the recent state, by the tendons of the Extensor muscles. In its upper half, it is divided by a ridge into two narrow lateral depressions, for the attachment of the Dorsal interossei muscles. This ridge bifurcates a little above the centre of the bone, and its branches run to the small tubercles on each side of the digital extremity.
The carpal extremity, or base, is of a cuboidal form, and broader behind than in front: it articulates, above, with the carpus; and on each side with the adjoining metacarpal bones; its dorsal and palmar surfaces being rough, for the attachment of tendons and ligaments.
The digital extremity, or head, presents an oblong surface, flattened at each side, for articulation with the first phalanx; it is broader and extends farther forwards in front than behind; and longer in the antero-posterior, than in the transverse diameter. On either side of the head is a deep depression, surmounted by a tubercle, for the attachment of the lateral ligament of the metacarpo-phalan-geal joint. The posterior surface, broad and flat, supports the Extensor tendons; and the anterior surface presents a median groove, bounded on each side by a tubercle, for the passage of the Flexor tendons.
PECULIAR METACARPAL BONES
The metacarpal bone of the thumb is shorter and wider than the rest, diverges to a greater degree from the carpus, and its palmar surface is directed inwards towards the palm, The shaft is flattened and broad on its dorsal aspect, and does not present the bifurcated ridge peculiar to the other metacarpal bones; concave from before backwards on its palmar surface. The carpal extremity, or base, presents a concavo-convex surface, for articulation with the trapezium, and has no lateral facets. The digital extremity is less convex than that of the other metacarpal bones, broader from side to side than from before backwards, and terminates anteriorly in a small articular eminence on each side, over which play two sesamoid bones.
The metacarpal bone of the index finger is the longest, and its base the largest of the other four. Its carpal extremity is prolonged upwards and inwards; and its dorsal and palmar surfaces are rough, for the attachment of tendons and ligaments. It presents four articular facets: one "*t the end of the bone, which has an angular depression for articulation with v. o trapezoid; on the radial side, a flat quadrilateral facet, for articulation with the trapezium; its ulnar side being prolonged upwards and inwards, to articulate above with the os magnum, internally with the third metacarpal bone.
The metacarpal bone of the middle finger is a little less in size than the preceding; it presents a pyramidal eminence on the radial side of its base (dorsal aspect), which extends upwards behind the os magnum. The carpal-articular facet is concave behind, flat and horizontal in front, and corresponds to the os magnum. On the radial side is a smooth, concave facet, for articulation with the second metacarpal bone; and on the ulnar side two small oval facets, for articulation with the third metacarpal.
The metacarpal bone of the ring-finger is shorter and smaller than the preceding, and its base small and quadrilateral; its carpal surface presenting two facets, for articulation with the unciform and os magnum. On the radial side are two oval facets, for articulation with the third metacarpal bone; and on the ulnar side a single concave facet, for the fifth metacarpal.
The metacarpal bone of the little finger may be distinguished by the concavo-convex form of its carpal surface, for articulation with the unciform, and from having only one lateral articular facet, which corresponds with the fourth metacarpal bone. On its ulnar side, is a prominent tubercle for the insertion of the tendon of the Extensor carpi ulnaris. The dorsal surface of the shaft is marked by an oblique ridge, which extends from near the inner side of the upper extremity, to the outer side of the lower. The outer division of this surface serves for the attachment of the fourth Dorsal interosseous muscle; the inner division is smooth, and covered by the Extensor tendons of the little finger.
Articulations. The first, with the trapezium; the second, with the trapezium, trapezoides, os magnum, and third metacarpal bones; the third, with the os magnum, and second and fourth metacarpal bones; the fourth, with the os magnum, unciform, and third and fifth metacarpal bones; and the fifth, with the unciform and fourth metacarpal.
Attachment of Muscles. To the metacarpal bone of the thumb, three: the Flexor ossis metacarpi pollicis, Extensor ossis metacarpi pollicis, and first Dorsal inter-osseous. To the second metacarpal bone, five: the Flexor carpi radialis, Extensor carpi radialis longior, first and second Dorsal interosseous, and first Palmar inter-osseous. To the third, five: the Extensor carpi radialis brevior, Flexor brevis pollicis, Adductor pollicis, and second and third Dorsal interosseous. To the fourth, three: the third and fourth Dorsal interosseous and second Palmar. To the fifth, four: the Extensor carpi ulnaris, Flexor carpi ulnaris, Flexor ossis metacarpi minimi digiti, and third Dorsal interosseous.
PHALANGES
The Phalanges are the bones of the fingers; they are fourteen in number, three for each finger and two for the thumb. They are long bones, and present for examination a shaft, and two extremities. The shaft tapers from above downwards, is convex posteriorly, concave in front from above downwards, flat from side to side, and marked laterally by rough ridges, which give attachment to the fibrous sheaths of the Flexor tendons. The metacarpal extremity or base, in the first row, presents an oval concave articular surface, broader from side to side, than from before backwards; and the same extremity in the other two rows, a double concavity separated by a longitudinal median ridge, extending from before backwards. The digital extremities are smaller than the others, and terminate, in the first and second row, in two small lateral conclyles, separated by a slight groove, the articular surface being prolonged farther forwards on the palmar, than on the dorsal surface, especially in the first row.
The Ungual phalanges are convex on their dorsal, flat on their palmar surfaces, they arc recognised by their small size, and from their ungual extremity presenting, on its palmar aspect, a roughened elevated surface of a horse-shoe form, which serves to support the sensitive pulp of the finger.
Articulations. The first row with the metacarpal bones, and the second row of phalanges; the second row, with the first and third; the third, with the second row.
Attachment of Muscles. To the base of the first phalanx of the thumb, four muscles: the Extensor primi internodii pollicis, Flexor brevis pollicis, Abductor pollicis, Adductor pollicis. To the second phalanx, two: the Flexor longus pollicis, and the Extensor secundi internodii. To the base of the first phalanx of the index finger, the first Dorsal and the first Palmar interosseus; to that of the middle finger, the second and third Dorsal iuterosseous; to the ring finger, the fourth Dorsal and the second Palmar interosseous; and to that of the little finger, the third Palmar interosseous, the Flexor brevis minimi digiti, and Abductor minimi digiti. To the second phalanges, the Flexor sublimis digitorum, Extensor com-munis digitorum; and, in addition, the Extensor indicis, to the index finger; the Extensor minimi digiti, to the little finger. To the third phalanges, the Flexor profundus digitorum and Extensor communis digitorum.
The Carpal bones are each developed by a single centre; at birth they are all cartilaginous. Ossification proceeds in the following order; in the os magnum and unciform an ossific point appears during the first year, the former preceding the latter; in the cuneiform, at the third year; in the trapezium and semi-lunar, at the fifth year, the former preceding the latter; in the scaphoid, at the sixth year; in the trapezoid, during the eighth year; and in the pisiform, about the twelfth year.
The Metacarpal bones are developed each by two centres: one for the shaft, and one for the digital extremity, for the four inner metacarpal bones; one for the shaft and one for the base, for the metacarpal bone of the thumb, which, in this respect, resembles the phalanges. Ossification commences in the centre of the shaft about the sixth week, and gradually proceeds to either end of the bone; about the third year the digital extremity of the four inner metacarpal bones and the base of the first metacarpal, commence to ossify, and they unite about the twentieth year.
The Phalanges are each developed by two centres: one for the shaft and one for the base. Ossification commences in the shaft, in all three rows, at about the sixth week, and gradually involves the whole of the bone excepting the upper extremity. Ossification of the base commences in the first row between the third and fourth years, and a year later in those of the second and third row. The two centres become united between the eighteenth and twentieth years.
Development of Hand
