io8 



Anatomy of Skeleton 



PS migwm 



on unciform, a postero-superior surface carrying a small facet for the fibre-cartilage, 

 but otherwise rough for ligaments, and an antero-superior (anterior) surface ligamen 

 tous, but with a facet on its inner part for the pisiform. 



Pisiform. A small nodular bone with an articular facet on its dorsal surface, 

 which rests on the front aspect of the cuneiform. Its long axis runs from above down- 

 wards and outwards, directed toward the hook of the unciform : the piso-uncinate 

 ligament is attached to the distal extremity, sometimes making a marked tubercle. 

 The tubercle is continuous with an oblique line visible on the radial aspect of the bone : 



the line gives attachment to the 

 anterior annular ligament and some 

 fibres of F. carpi ulnaris, the re- 

 mainder of the tendon running on 

 to the proximal and palmar sur- 

 faces of the bone. A slightly hol- 

 lowed surface lies between the 

 radial line and the dorsal articula- 

 tion, increasing in depth as it is 

 traced in a proximal direction, and 

 making, at this end, a characteris- 

 tic hollow on the radial side which 

 enables the observer to recognise 

 the upper end and the outer 

 aspect. The inner or ulnar surface 

 is marked by faint striations from 

 fibres of the posterior annular liga- 

 ment which reach it. In front of 

 these, between them and the 

 tubercle for the piso-uncinate liga- 

 ment, is an area for attachment of 

 piso-metacarpal fibres. The Ab- 

 ductor minimi digiti arises from 

 the front of the bone between these 

 various areas, and extends on to 

 the different ligamentous fibres 

 occupying the surrounding surfaces. 

 The deep hollow at its proximal 

 (radial) side is occupied by a fibrous pad connecting the flexor sheath with the posterior 

 annular ligament. 



Trapezium. Upper surface has facet slightly concave from before backwards for 

 scaphoid, and outside and behind this a ligamentous area for external lateral ligament. 

 An internal surface concave from above down for articulation with trapezoid. The 

 bone has its lower back and inner part prolonged down to articulate with the outer 

 side of the base of the metacarpal of index finger, so that its lower aspect shows this 

 facet looking downwards and inwards, and further out and proximally a concavo- 

 convex surface for the metacarpal of the thumb looking downwards and outwards. 



The front surface is on the whole somewhat flattened, giving attachment to 

 ligaments and to Opponens and Abductor pollicis, and insertion at its outer part to 

 Extensor ossis metacarpi. Its inner margin forms a prominent ridge for attachment 



3a Supporting radial Oft 

 paJnir iurfice 



Tuptyum 



Suphud. 



tforJdi 'surface 



FIG. 88. Upper figures, left trapezium 



external aspect ; 2, palmar aspect. To distinguish 

 left from right, hold the bone so that the deep groove 

 for Fl. carp. rad. is in front and near the proximal 

 part of the bone, running towards the index finger, 

 while the concavo-convex facet for first metacarpal 

 looks toward the thumb. Lower figures, left trapezoid : 

 I, outer and 2, inner views. To distinguish the 

 sides, place the smaller non-articular surface in front, 

 with the pointed downward prolongation from it 

 toward the outer side ; of the two articular areas 

 between which this prolongation lies the larger saddle- 

 shaped one should look toward the index finger, and 

 the smaller convex one outwards. (See text.) 



I, postero- 



