320 HUMAN ANATOM\. 



apt to be near the distal end, although the thinnest and weakest parts of the bones 

 are just above the middle and they sometimes break there. The proximal fragment 

 is held iirmly by its ligamentous attachments and is less movable than the phalangeal 

 portion ; its distal end may project on the dorsum. The knuckle of the affected 

 finger sinks and partially disappears. The lumbricales and the interossei aid in 

 producing this deformity, and may cause the proximal end of the distal fragment to 

 become prominent on the dorsum of the hand. In examining for these fractures it 

 should be remembered that the metacarpal bones of the index- and middle fingers are 

 bound tightly to the carpus and possess but little power of independent movement. 

 The others are more movable. In the treatment of these fractures the normal palmar 

 concavity of the metacarpal bones should never be forgotten. 



The Phalanges. — Epiphyseal separation of the phalanges is extremely rare. 

 The epiphyses are all at the upper ends of the bones. The diagnosis from severe 

 sprain or from fracture will usually be made by the X-rays. It is now thought that not 

 a few of the cases of necrosis of the proximal end of a phalanx following acute inflam- 

 mation or whitlow are the result of epiphyseal sprain or disjunction. Of course, 

 necrosis is often the sequel of the spread of infection from the superficial structures 

 of the hand to the closely applied fibro-cellular tissue over the terminal phalanges. 



Fractures occur most frequently in the proximal and most rarely in the ter- 

 minal phalanges. The relation of the tendons on the dorsal and palmar surfaces 

 usually prevents any marked displacement. Occasionally an anterior angular de- 

 formity of the proximal phalanx is seen after fracture. It is believed to be favored 

 by the action of the interossei. 



The frequency with which both tuberculous and syphilitic inflammations affect 

 the phalanges is probably due to their exposure to slight injury. They are, how- 

 ever, not often the subject of post-typhoidal infection. The cause of whitlow has 

 already been mentioned, and will be recurred to. The reason for the over- 

 growth of the bony structures of the hand in acromegaly and in hypertrophic pul- 

 monary osteo-arthropathy is not known. In the latter case it has been suggested 

 that the enlargement of the terminal phalanges, like the " clubbing" of the fingers in 

 phthisical patients, may be due to an osteogenetic stimulus derived from the pres- 

 ence in the circulation of the secondary products of the pulmonary infection. This 

 would be analogous to the increased rapidity of growth observed in adolescents 

 during convalescence from typhoid. 



Landmarks. — On the inner side of the hand, below the wrist, the pisiform 

 bone can be felt, and when grasped firmly can be given slight lateral movement. 

 Lower and more externally the hook of the unciform can be made out. On the 

 outer side the tuberosity of the scaphoid just below and internal to the radial sty- 

 loid and still lower the ridge of the trapezium may both be felt. With the hand 

 in full flexion, the dorsal prominence of the scaphoid and semilunar and the curved 

 line of their articulation with the radius may be felt ; the anterior and posterior 

 lips of the articular surface of the latter bone can be palpated and the groove or 

 depression beneath them recognized. The projection of the os magnum on the 

 back of the hand, and occasionally of the base of the third metacarpal at its articu- 

 lation with the OS magnum, may easily be felt. When an unusual prominence of these 

 bones exists, and is first noticed after a fall or strain, it sometimes leads to a mis- 

 taken diagnosis of exostosis or of ganglion. 



The metacarpal bones, their concavity, their expanded anterior extremities form- 

 ing the knuckles, the shape and size of the shafts and ends of the phalanges, and of 

 their articulations with the metacarpus and with each other, can all readily be made 

 out through or between the overlying tendons. 



The surface markings of the hand and of its joints will be considered later (page 

 621.) 



LIGAMENTS OF THE WRIST AND METACARPUS. 



The ligaments and joints of the wrist include three articulations, the radio- 

 carpal, the intracarpal, and the carpo-metacarpal, which often receive detailed 

 separate description. The simpler and in many ways more desirable conception of 

 these joints is to regard them as parts of a common articulation consisting of a 



