THE HAND 91 



thickened portion of the deep fascia on the back of the wrist. 

 It is attached to the volar (anterior) border and styloid process 

 of the radius, and it passes obliquely across the dorsum of the 

 wrist, to be attached to the styloid process of the ulna and the 

 medial border of the carpus. Septa unite its deep surface to 

 the dorsal aspect of the radius, and form complete osteo-fascial 

 tunnels for the extensor tendons. 



Synovial Sheaths of Extensor Tendons. Synovial sheaths 

 invest the extensor tendons as they lie under cover of the dorsal 

 carpal ligament. They extend for a short distance proximal 

 to the ligament and distally for an inch or more beyond it. Six 

 sheaths are present at the back of the wrist, and they surround 

 the tendons of : 



1. Abductor pollicis longus (Ext. oss. metacarp) and Ext. pollicis brevis. 



2. Ext. carpi radialis longus and brevis. 



3. Ext. pollicis longus. At the point where this tendon crosses the radial 

 extensors of the wrist, the two synovial sheaths communicate freely. 



4. Ext. digitorum communis and indicis proprius. 



5. Ext. digiti quinti proprius. 



6. Ext. carpi ulnaris. 



The characteristic " new leather creaking " of teno-synovitis 

 in this region is due to friction between the inflamed " visceral " 

 and parietal layers of the tendon sheaths. The tendons of the 

 radial extensors are most commonly affected. 



Carpal Ganglion, which usually occurs in relation to the 

 tendons of the radial extensors of the wrist, may or may not be 

 continuous with their sheaths. According to some authorities 

 it may arise from a degeneration of the ligaments in this region 

 or from the bursae which are situated immediately beneath the 

 insertions of these tendons. 



The Dorsal Subaponeurotic Space. On the dorsum of the 

 hand the extensor tendons of the ringers are united to one 

 another by oblique bands in such a way as to form with the deep 

 fascia an aponeurotic sheet, which is attached, on each side, 

 to the borders of the second and fifth metacarpals. The dorsal 

 subaponeurotic space (Kanavel) lies between this sheet and the 

 dorsal surfaces of the medial four metacarpals and interosseous 

 muscles. Septic infection of the space is generally primary, 

 following wounds on the dorsum. It may be involved secondarily 

 to infections of the middle palmar space (p. 90), but it is never 

 infected from the thenar space (p. 90). When pus collects in 

 this situation it is limited distally at the metacarpo-phalangeal 



