362 



APPLIED ANATOMY. 



DISLOCATIONS OF THE HAND. 



The carpal bones are so firmly held in place by their ligaments that they are 

 rarely luxated. Dislocations of the scaphoid and semilunar however are sometimes 

 encountered. 



Dislocations of the Bases of the Metacarpal Bones. Dislocations 

 sometimes occur toward the dorsal surface. The bases of the second and third met- 

 acarpal bones in the uninjured hand form a bony prominence on the dorsum of the 



FIG. 375. Dislocation of proximal phalanx of little finger. (From author's sketch.) 



hand which may be mistaken for a luxation. This prominence lies in a direct 

 line with the posterior radial (or thecal) tubercle and about 4 cm. (i^ in.) below it. 



The bases of the metacarpal bones and carpometacarpal joints are best recog- 

 nized by following up the interosseous spaces by making firm pressure with the 

 fingers between the bones ; when the upper limit of the space is reached the joints 

 can be located 1.25 cm. (^ in.) above. 



Dislocations of the Phalanges on the Metacarpal Bones. These dislo- 

 cations occur with moderate frequency. Dislocation of the thumb occurs most 

 frequently and is well known. The little finger is next in frequency, while the other 



FIG. 376. Dorsal luxation of the proximal phalanx of the thumb, showing the position of the bones. 



three are rarely luxated. When luxation of the proximal phalanx of the little finger 

 occurs it acts precisely as does that of the thumb (as I have seen in one case, Fig. 

 375). As the thumb dislocation is the most troublesome it alone will be described. 

 Dislocation, of the Proximal Phalanx of the Thumb. This displacement occurs 

 when the thumb is hyperextended on its metacarpal bone (Figs. 376 and 377), and it 

 is often impossible to reduce it without division of the resisting structures. The 

 head of the metacarpal bone is much larger than the shaft immediately behind it and 

 projects especially on its palmar surface toward each side, forming two tubercles. 



