THE HAND. 



3 6 3 



The joint has two lateral ligaments and an anterior or glenoid ligament. These 

 are more firmly attached to the phalanx than to the metacarpal bone, so that in 

 dislocation they are torn from the latter. 



Inserting into the outer side of the base of the proximal phalanx are the tendons 

 of the abductor and outer head of the flexor brevis pollicis. They blend with the 

 lateral ligament and have developed in them a sesamoid bone which rides on the 

 tubercle. 



Inserting into the inner side of the base of the proximal phalanx are the inner 

 head of the flexor brevis and the adductor obliquus and transversus pollicis muscles. 

 They blend with the lateral ligament and contain a sesamoid bone which rides on the 



Abductor pollicis 

 Flexor brevis pollicis 



Flexor longus pollicis 



Fin. 377. Dorsal luxation of the proximal phalanx of the thumb: Division of the tendons of the abductor and 



flexor brevis pollicis muscles. 



inner tubercle. The flexor longus pollicis tendon passes between the two tubercles 

 and sesamoid bones. 



When the thumb is hyperextended the glenoid and lateral ligaments are torn 

 loose from the metacarpal bone and carry with them the tendons and sesamoid bones 

 already described. The head of the metacarpal bone projects forward in the palm 

 and can be felt beneath the skin ; the flexor longus pollicis tendon slips to the inner 

 side of the bone. As the head pierces the capsule the latter, strengthened by the 

 tendons of the short muscles of the thumb, 

 contracts behind it like a collar and pre- 

 vents reduction. 



Reduction is to be attempted by ex- 

 tending the phalanx until it is at right 

 angles with the metacarpal bone and drag- 

 ging its base forward over the head of the 

 metacarpal bone and then flexing. 



If this is not successful, then by means 

 of a narrow knife, either through an open 

 wound or subcutaneously, the lateral ligament and tendons on one side (the radial) 

 are loosened from the base of the phalanx, which can then be brought forward. 

 This, of course, divides the tendinous collar which prevents reposition (Fig. 377). 



Dislocations of the Middle and Distal Phalanges. These frequently 

 occur in playing ball games. In attempting to catch the ball the tip of the finger 

 may be struck and the phalanx hyperextended and thereby luxated (Fig. 378). 



These luxations are usually readily reduced by simple traction and flexion. 

 Sometimes, however, reduction is not complete, or there is a concomitant fracture, 

 hence the crippled and deformed fingers so often seen in the case of base-ball players. 



A tearing loose of the attachment of the extensor tendon allows the distal 

 phalanx to fall, producing what Stern has called drop phalangette. 



FIG. 378. Dislocation of the terminal phalanx, show- 

 ing the position of the bones. (From author's sketch.) 



