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here also the transverse carpal ligament is attached. The ulnar artery and nerve are in immediate relation with the lateral side of the bone.
Os Multangulum Majus (O.T. Trapezium). The greater multangular is the most lateral bone of multangular the distal row of the carpus. It may be readily recognised by the oval saddle-shaped facet on its distal surface for articulation with the metacarpal bone of the thumb. From its volar aspect there rises a prominent ridge, medial to which is a groove along which the tendon of the flexor carpi radialis muscle passes. The ridge furnishes an attachment for the transverse carpal ligament, as well as for some of the short muscles of the thumb. The proximal surface has a halfoval facet for the navicular, lateral to which it is rough, and becomes continuous with the non-articular lateral aspect, which serves for the attachment of ligaments. On its medial surface there are two facets; the proximal is a half-oval,
concave proximo-distally, and very slightly convex from volar to dorsal side, and is for articulation with the lesser multangular; the distal, small and circular, and not always present, is for articulation with the lateral side of the base of the second metacarpal bone. The dorsal surface, of irregular outline, is rough for the attachment of ligaments. The greater multangular articulates with four bones, the navicular, lesser multangular, and the first and second metacarpal bones.
FIG. 213. THE RIGHT NAVICULAR BONE.
NOTE. The bone is represented in the centre of the figure in the position which it occupies in the right hand viewed from the volar aspect. The views on either side, and above and below, represent respectively the corresponding surfaces
of the bone turned towards the reader.
Os Multangulum Minus (O.T. Trapezoid Bone).-With the exception of the pisiform, the lesser multangular is the smallest of the carpal bones. Its rough volar surface is small and pentagonal in outline. By a small oblong area on its proximal surface it articulates with the navicular. Distally, by a somewhat saddle-shaped surface, it articulates with the base of the second metacarpal. Separated from this by a rough V-shaped impression prolonged from its volar aspect, is the area on the lateral surface for articulation with the greater multangular; this is obliquely grooved from before backwards and distally. The medial facet, for articulation with the capitate, is narrow proximo-distally, and deeply curved from before backwards. The dorsal surface of the bone, which is rough and non-articular, is much larger than the volar aspect. The mass of the bone,
FIG. 214.-THE RIGHT OS LUNATUM.
NOTE.-The bone is represented in the centre of the figure in the
position which it occupies in the right hand viewed from the volar aspect. The views on either side, and above and below, represent respectively the corresponding surfaces of the bone turned towards the reader.
dorsally, is directed distally and towards the medial side. The lesser multangular articulates with four bones-the greater multangular, navicular, and capitate bones, and the second metacarpal.
Os Capitatum (O.T. Os Magnum). -This is the largest of the carpal bones. Its volar surface is rough and rounded. The proximal portion of the bone forms the head, and is furnished with convex articular facets which fit into the hollows on the medial surface of the navicular and distal surface of the os lunatum; that for the latter is medial to and separated by a slight ridge from the navicular articular area. The distal surface, narrow towards its volar border and broad dorsally, is subdivided usually into three facets by two ridges-that towards the lateral side is for the base of the second metacarpal; the intermediate facet is for the third metacarpal ; whilst the medial facet of the three, not always present, very small and placed near the dorsal side of the bone, is for the fourth metacarpal. The lateral surface of the body has an articular area for the lesser multangular, not infrequently separated from the navicular surface on the head by a rough line, to which the interosseous ligament connecting it with the navicular is attached. The medial surface of the body has an elongated articular area, usually deeply notched in front; or it may be divided anteriorly into a small circular area near the dorsal edge, and a larger posterior part. This latter articulates either singly or doubly with the os hamatum, the interosseous ligament which unites the two bones being attached either to the notch or to the surface separating the two articular facets. The dorsal surface is rough for ligaments; it is somewhat constricted below the head, the articular surface of which sweeps round its proximal border.
The capitate bone articulates with seven bones-the os hamatum, the os lunatum, the navicular, the lesser multangular, and the second, third, and fourth metacarpal bones; occasionally
NOTE.-The figure to the left represents the volar aspect of the bone; that to the right the dorsal view.
Os luna. tum
FIG. 215. THE RIGHT OS TRIQUETRUM. NOTE.-The bone is represented in the centre of the figure in the position which it occupies in the right hand viewed from the volar aspect. The views on either side, and above and below, represent respectively the corresponding surfaces of the bone turned towards the reader.
FIG. 217. THE RIGHT GREATER MULTANGULAR BONE.
in the position which it occupies in the right hand
towards the reader.
the corresponding surfaces of the bone turned Os Hamatum (O.T. Unciform Bone). The os hamatum can be readily distinguished by the hook-like process (hamulus) which projects from the distal and
medial aspect of its volar surface. To this is attached the transverse carpal
ligament as well as some of the fibres of origin of the short muscles of the little finger. The medial side of the hamulus is sometimes grooved by the deep branch of the ulnar nerve. (Anderson, W.," Proc. Anat. Soc." Journ. Anat. and Physiol. vol. xxviii. p. 11.) The volar surface, rough for ligaments, is somewhat triangular in shape Proximally and towards the medial side there is an elongated articular surface for the os triquetrum, convex proximally and concave distally. The lateral aspect of the bone is provided with a plane elongated facet, occasionally divided into two for articulation with the capitate bone (see above). Where the proximal and lateral surfaces meet, the angle is blunt, and has a narrow facet which articulates with the os lunatum. Distally there are two articular facets separated by a ridge; these are slightly concave from before backwards, and are for articulation, the lateral with the fourth, and the medial with the fifth metacarpal bone. The dorsal surface, more or less triangular in shape, is rough for liga
The os hamatum articulates with five bones-viz., the capitate, os lunatum, os triquetrum, and the fourth and fifth metacarpals.
FIG. 218. THE RIGHT LESSER MULTANGULAR BONE.
NOTE.-The bone is represented in the centre of the figure in the position which it occupies in the right hand viewed from the volar aspect. The views on either side, and above and below, represent respectively the corresponding
surfaces of the bone turned towards the reader.
The Carpus as a
When the carpal bones are articulated together they form a bony mass, the dorsal surface of which is convex from side to side. Anteriorly they present a grooved appearance, concave from side to side. This arrangement is further emphasised by the forward projection, onthe medial side, of the pisiform and hamulus of the os hamatum, whilst laterally the tuberosity of the navicular and the ridge
of the greater multangular help to deepen the furrow'by their elevation. To these
Lesser multangular bone
FIG. 219.-THE RIGHT CAPITATE BONE.
The bone is represented in the centre of the figure in the position which it occupies in the right hand viewed from the volar aspect. The views on either side, and above and below, represent respectively the corresponding surfaces of the bone turned towards the reader.
four points the transverse carpal ligament is attached, which stretches across from
side to side, and thus converts the furrow into a canal through which the flexor tendons pass to reach
IV. Metacarpal the fingers.
FIG. 220.-THE RIGHT OS HAMATUM.
NOTE.-The bone is represented in the centre of the figure in the position which it occupies in the right hand viewed from the volar aspect. The views on either side, and above and below, represent respectively the corresponding surfaces of the bone turned towards the reader.
Ossification. At birth the carpus is entirely cartilaginous. An exceptional case is figured by Lambertz, in which the centres for the capitate and triquetral bones were already present. The same authority states that it is not uncommon to meet with these centres in the second month after birth. According to Debierre (Journ. de l'Anat. et de la Physiol. vol. xxii. 1886, p. 285), ossification takes place approximately as follows:
It will be noticed that whilst the primary centres for the metacarpus and phalanges are well ossified, the carpus is still entirely cartilaginous. Compare this with the tarsus at birth, in which the tarsus is shown in part already ossified.
11 to 12 months.
12 to 14 months.
5 to 6 years.
6 to 7 years.
10 to 12 years.
The same observer failed to note the appearance of a separate centre for the hamulus of the os hamatum, and records the occurrence of two centres for the pisiform.
The metacarpal bones form the skeleton of the palm, articulating proximally with the carpus, whilst by their distal extremities or heads they support the bones of the digits. Five in number, one for each digit, they lie side by side and slightly divergent from each other, being separated by intervals, termed interosseous spaces. Distinguished numerically from the lateral to the medial side, they all display certain common characters; each possesses a body or shaft, a base or carpal extremity, and a head or phalangeal end.
The bodies, which are slightly curved towards the volar aspect, are narrowest towards their middle. The dorsal surface of each is marked by two divergent lines which pass distally from the dorsum of the base to tubercles on either side of the
head. The surface included between the two lines is smooth and of elongated triangular form. On either side of these lines two broad shallow grooves wind spirally on to the volar surface, where they are separated by a sharp ridge which is continuous with a somewhat triangular surface which corresponds to the volar aspect of the base. The grooved surfaces on either side of the shaft furnish origins for the interossei muscles. Close to the volar crest is the opening of the nutrient canal, which is directed towards the proximal extremity, except in the case of the first metacarpal bone.
The capitulum (head) is provided with a surface for articulation with the proximal phalanx. This area curves farther over its volar than its dorsal aspect. Convex from before backwards and from side to side, it is wider anteriorly than posteriorly; notched on its volar aspect, its edges form two prominent tubercles, which are sometimes grooved for the small sesamoid bones which may occasionally be found on the volar surface of the joint. On either side of the head of the bone there is a deep pit, behind which is a prominent tubercle; to these are attached the collateral ligaments of the metacarpo-phalangeal joints.
all more or less wedge-shaped in form, articulate with the carpus; they differ in size and shape according to their articulation.
Of the five metacarpal bones, the first, viz., that of the thumb, is the shortest and stoutest, the second is the longest, whilst the third, fourth, and fifth display a gradual reduction in length.
The medial four bones articulate by their bases with each other, and are united at their distal extremities by ligaments. They are so arranged as to conform to the hollow of the palm, being concave from side to side anteriorly, and convex posteriorly. The first metacarpal differs from the others in being free at its distal extremity, whilst its proximal end possesses only a carpal articular facet.
The first metacarpal bone is the shortest and stoutest of the series. Its body is compressed from before backwards. Its head, of large size, is but slightly convex from side to side, and is grooved on its volar aspect for the sesamoid bones. The base is provided with a saddle-shaped surface for articulation with the greater multangular, and has no facets on its sides. Laterally there is a slight tubercle to which the abductor pollicis
FIG. 223.-SECOND RIGHT METACARPAL BONE.
NOTE.-The bone is represented in the centre of the figure in the position which it occupies in the right hand viewed from the volar aspect. The views on either side, and below, represent respectively the corresponding surfaces of the bone turned towards the reader.