Limbs : Upper Limb 



1 1 1 



they are, moreover, attached to each other at their distal ends by the transverse meta- 

 carpal ligament, which lies on the palmar aspect of the heads of the inner four bones 

 and is attached to them through the capsule of the metacarpo-phalangeal joint. They 

 are arranged in a somewhat radiating fashion, and make a palmar concavity, and the 

 intervals between them are filled up by the interosseous muscles : the concavity con- 

 tains the flexor sheath and, deep to this in the outer part of the palm, the adductors 

 of the thumb, while the deep palmar vessels and nerve cross it near the bases of the 

 bones. Their dorsal surfaces are covered by the plane of extensor tendons, and the 

 dorsal interosseous fascia extends from bone to bone between them. 



The different metacarpals can be easily recognised, but it is well first to observe 

 the general distinctions in appearance 



between the metacarpals and meta- pa .lma.r. 



tarsals, as shown in Fig. 85. The 

 proximal ends of the metacarpals are 

 distinctive. 



First, or Thumb, Metacarpal (Fig. 

 90). Sometimes confounded with 

 phalanges : distinguished by its 

 simple rounded head and its basal 

 concavo-convex surface for articula- 

 tion with trapezium. Shaft is broad 

 and rather flattened. A small facetted 

 tubercle on the outer side of the 

 proximal end is for insertion of 

 Extensor ossis metacarpi, and may 

 be used to aid in placing the bone on 

 its proper side ; but the tubercle is 

 often indistinct, and there may be a 

 large Jigamentous tubercle on the inner 

 side. The saddle-shaped surface for 

 trapezium is divided by a low ridge 

 running anterc-posteriorly, and the 

 Fig. 90. 



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 ridge V 



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.iu.tt: 



FIG. 90. First right metacarpal. The side to which 

 the bone belongs can be ascertained by looking 

 at the proximal articular surface ; the outer slope 

 of the saddle-shaped surface is larger, x, origin of 

 deep head of F. brevis pollicis. 



larger subdivision is external, as shown in 



Second, or Index, Metacarpal. Recognised at once by the deep cleft or groove 

 running antero-posteriorly across its carpal surface, as shown* in Fig. 91, for articula- 

 tion with the trapezoid : it is very apparent when looked yat from the dorsal side. 

 The bone touches the middle metacarpal, and therefore has a metacarpal facet on its 

 inner side, and this is separated from the basal surface by a bevelled-off area for the 

 os magnum. On the outer side there is no metacarpal facet, but a small rounded 

 or four-sided surface looking forwards, outwards and upwards for the trapezium : 

 immediately behind this is a roughened facetted dorsal area fcr the insertion of 

 Extensor carpi radialis longior. 



Third, or Middle-Finger, Metacarpal. Recognised by its styloid process, which 

 also is on the outer side of its basal end behind : from this the bone can be placed 

 on its proper side. There is only one carpal facet, but metacarpal facets are on both 

 sides. Observe that these are divided into anterior and posterior parts, partly on 



