488 



THE MUSCLES AND FASCIAE 



of tendons, with the exception of those of the thumb and little finger; in each 

 of these two digits the diverticulum is continued on, and communicates with the 

 synovial sheath of the tendons in the fingers. In the other three fingers the syno- 

 vial sheath of the tendons begins as a blind pouch without communication with 

 the large synovial sac (Fig. 365). 



Applied Anatomy. This arrangement of the synovial sheaths explains the fact that thecal 

 abscess in the thumb or little finger is liable to be followed by abscesses of the forearm, from 

 extension of the inflammation along the continuous synovial . sheaths. Tuberculous inflamma- 

 tion is liable to occur in this situation, 

 constituting compound palmar ganglion; it 

 presents an hour-glass outline, with a 

 swelling in front of the wrist and in the 

 palm of the hand, and a constriction corre- 

 sponding to the annular ligament between 

 the two. The fluid can be forced from the 

 one swelling to the other under the liga- 

 ment. 



Bursse about the Hand and Wrist. 

 Bursse usually exist between the distal ex- 

 tremities of the metacarpal bones (bursae 

 intermetacarpophalangeae), and a subcuta- 

 neous bursa often exists over the dorsal 

 surface of4hejiead of the fifth metacarpal 

 bone. Subcutaneous digital dorsal bursse 

 occur "almost constantly in the first finger- 

 joints (between the first and second pha- 

 lanx), occasionally in the second joint of 

 the second and fourth fingers" 1 (bursae sub- 

 cutaneae digitorum dorsales). A bursa exists 

 between the tendon of the Extensor carpi 

 radialis brevior and the base of the third 

 metacarpal bone; another between the 

 Flexor carpi ulnaris and the pisiform bone; 

 another between the Flexor carpi radialis 

 and the base of the second metacarpal bone. 



Fie. 365. Diagram showing-the arrangement of the 

 synovial sheaths of the palm and fingers. 



The Posterior Annular Ligament 

 (ligamentum carpi dorsale) is a strong 

 fibrous band extending obliquely 

 downward and inward across the 

 back of the wrist, and consisting of 

 the deep fascia of the back of the 

 forearm, strengthened by the addition 

 of some transverse fibres. It binds 

 down the Extensor tendons in their 

 passage to the fingers, being attached, 

 internally, to the styloid process of 

 the ulna, the cuneiform and pisiform 

 bones; externally, to the margin of the 

 radius; and, in its passage across the 

 wrist, to the ridges on the posterior 

 surface of the radius. It presents six 

 compartments for the passage of ten- 

 dons, each of which is lined with a separate synovial membrane (Fig. 366). These 

 are, from without inward: (1) On the outer side of the styloid process, for the 

 tendons of the Extensor ossis metacarpi and Extensor brevis pollicis. (2) Behind 

 the styloid process, for the tendons of the Extensor carpi radialis longior and 



FIG. 366. Transverse section through the wrist, show- 

 ing the annular ligaments and the canals for the passage 

 of the tendons. 



1 Hand Atlas of Human Anatomy. By Werner Spalteholz. Translated and edited by Lewellys F. Barker. 



