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 multCapitate angular is the most lateral bone of Greater multangular the distal row of the carpus. It Lesser multangular may be readily recognised by the oval saddle-shaped facet on its distal surface for articulation with Capitate 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 Radius passes. The ridge furnishes an attachment for the transverse Radius carpal ligament, as well as for some of the short muscles of the thumb. Os lunatum The proximal surface has a halfoval facet for the navicular, lateral to which it is rough, and becomes Fig. 213.—THE RIGHT NAVICULAR BONE. continuous with the non-articular Note. —"The bone is represented in the centre of the figure lateral aspect, which serves for from the volar aspect . The views on either side, and above the attachment of ligaments. On and below, represent respectively the corresponding surfaces its medial surface there are two of the bone turned towards the reader. 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. Thegreater multangular articulates with Capitate Os triquetrum four bones, the navicular, lesser multangular, and the first and second metacarpal bones. Os hamatum Os hamatum 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 Radius and pentagonal in outline. Navicular 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. Fig. 214. - The Right Os LUNATUM. Separated from this by a rough Nore.—The bone is represented in the centre of the figure in the V-shaped impression prolonged position which it occupies in the right hand viewed from the from its volar aspect, is the volar aspect. The views on either side, and above and below, represent respectively the corresponding surfaces of the bone area on the lateral surface for turned towards the reader. 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, dorsally, is directed distally and towards the medial side. The lesser multangular articulates with four bones—the greater multangular, navicular, and capitate Os hamatum Os lunatum bones, and the second metacarpal. Os Capitatum (O.T. Os Magnum). Pisiform Pisiform Os hamatum wards its volar border and broad dorsally, is subdivided usually into three facets by two ridges—that towards the lateral side Articular disc is for the base of the second metacarpal; of wrist Os luna the intermedia te facet is for Fig. 215.—THE Right Os TRIQUETRUM. the third Note: - The bone is represented in the centre of the figure in the position which it occupies in the right hand metacarpal ; viewed from the volar aspect. The views on either Os triquetrum whilst the side, and above and below, represent respectively the corresponding surfaces of the bone turned FIG. 216.—THE RIGHT PISIFORM medial facet towards the reader. Bone. of the three, NOTE.— The figure to the left repre- not always present, very small and placed near the dorsal sents the volar aspect of the side of the bone, is for the fourth metacarpal. The lateral bone; that to the right the dorsal view. surface of the body has an articular area for the lesser multangular, not infrequently separated from the navic ular surface on the head by a rough line, to which the interosseous ligament connecting it with the navicular is atSmall tached. The medial surface of the body multangular I. Metacarpal has an elongated articular area, usuII. Metac. II Metac. ally 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 articu lar facets. The dorsal surface is rough Navicular Ridge 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 multFig. 217.—THE RIGHT GREATER MULTANGULAR BONE. angular, and the second, third, and NOTE.—The bone is represented in the centre of the figure in the position which it occupies in the right hand fourth metacarpal bones; occasionally viewed from the volar aspect. The views on either the fourth metacarpal does not arside, and above and below, represent respectively ticulate with the capitate. the corresponding surfaces of the bone turned Os Hamatum (O.T. Unciform towards the reader. Bone).—The os hamatum can be readily distinguished by the hook-like process (hamulus) which projects from the distal and Greater Navicular 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 Capitate bone II. Metacarpal 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 elonmultangular gated facet, occasionally divided into two for articulation with the capitate bone (see above). Where the proximal and lateral surfaces Fig. 218.–The Right LESSER MULTANGULAR BONE. Note. — The bone is represented in the centre of the figure in meet, the angle is blunt, and has the position which it occupies in the right hand viewed a narrow facet which articulates from the volar aspect. The views on either side, and with the os lunatum. Distally above and below, represent respectively the corresponding there are two articular facets surfaces of the bone turned towards the reader. 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 II. Metacarpal bone. The dorsal surface, more or less triangular in IV. Metacarpal II. Metacarpal shape, is rough for ligaments. The os hamatum articulates with five bones-viz., III. Metacarpal the capitate, os lunatum, os 111. Metacarpal triquetrum, and the fourth and fifth metacarpals. Os hamatum IV, Metacarpal Lesser multangular bone The Carpus as a Whole. are Os lunatum Navicular When the carpal bones articulated together they form a bony mass, the -Os lunatum dorsal surface of which is convex from side to side. Anteriorly they present a grooved appearance, con Os hamatum cave from side to side. This arrangement is further emphasised by the forward Fig. 219.–The Right CAPITATE BONE. projection, onthe medialside, of the pisiform and hamulus Note..--The bone is represented in the centre of the figure in the position which it occupies in the right hand viewed from the of the os hamatum, whilst volar aspect. The views on either side, and above and below, laterally the tuberosity of represent respectively the corresponding surfaces of the bone turned the navicular and the ridge towards the reader. of the greater multangular help to deepen the furrow'by their elevation. To these 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 V. Metacarpal IV. Metacarpal the fingers. Fig. 221.-RADIOGRAPH OF THE Os lunatum HAND AT BIRTH. It will be noticed that whilst the FI 220.—THE RIGHT Os HAMATUM, primary centres for the metacarpus and phalanges are well ossified, the NOTE.— The bone is represented in the centre of the figure in the position carpus is still entirely cartilaginous. which it occupies in the right hand viewed from the volar aspect. Compare this with the tarsus at The views on either side, and above and below, represent respectively birth, in which the tarsus is shown the corresponding surfaces of the bone turned towards the reader. in part already ossified. . 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 :Capitate bone 11 to 12 months. Os hamatum 12 to 14 months. Os triquetrum 3 years. 6 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. 5 to 6 years. 6 years. A The Metacarpus. 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, wbich 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 Shaft Base Head Tubercle 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. The bases, all more or less wedge-shaped in Fig. 222.- FIRST RIGHT form, METACARPAL BONE. 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, Lesser and convex posteriorly. The multangular first metacarpal differs from Greater the others in being free at Capitate bone multangular its distal extremity, whilst its proximal end possesses only a carpal articular facet. The first metacarpal bone is the shortest and Lesser multangular stoutest of the series. Its Fig. 223.-SECOND RIGHT METACARPAL BONE. body is compressed from Note. — The bone is represented in the centre of the figure in the before backwards. Its head, position which it occupies in the right hand viewed from the volar aspect. The views on either side, and below, represent respectively of large size, is but slightly the corresponding surfaces of the bone turned towards the reader. 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 Shaft III. Metac. Base Medial side Lateral side |
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