THE FOREARM AND WRIST 79 



joint of the thumb (p. 84) and the joint between the pisiform 

 and the os triquetrum cuneiform), all the inter-carpal, carpo- 

 metacarpal, and inter-metacarpal joints have a common joint 

 cavity lined with a single synovial membrane. Their volar 

 (palmar) and dorsal ligaments are continuous with the corre- 

 sponding ligaments of the radio-carpal joint (p. 76). 



Ossification of the Carpus. At the end of the first year 

 centres appear for the capitate (os magnum) and hamate 

 (unciform) bones. These are followed by centres for the 

 triquetrate (cuneiform), third year ; the lunate (semilunar), 

 fifth year ; the greater multangular (trapezium), sixth year ; 

 the navicular (scaphoid), sixth year ; the lesser multangular 

 (trapezoid), seventh year ; and the pisiform about the tenth 

 year. 



Spread of Tuberculous Disease in the Wrist Region. 

 The capsules of the distal radio-ulnar and the radio-carpal 

 joints do not encroach on the diaphyses, and, consequently, 

 tuberculous disease in the distal ends of the diaphyses of the 

 radius and ulna is extra- cap sular . When it breaks out under 

 the periosteum, it does not commonly spread distally to the 

 joints, unless it erupts in the region where the synovial membrane 

 of the distal radio-ulnar joint pouches proximally between the 

 two bones (p. 75). 



The carpal bones are really within the capsule of the wrist- 

 joint, and tuberculous disease arising in them is intra-capsular 

 and readily reaches the joint by penetrating the articular 

 cartilage. If the disease spreads forwards or backwards, 

 perforating the ligaments, the synovial sheaths of the tendons 

 become affected ; but a sympathetic effusion may occur into the 

 sheaths while the disease is still confined to the joint, and it 

 may set up adhesions, which limit the movements of the muscles 

 concerned. 



Surgical Approach to the Wrist - Joint. Pyogenic 

 infections of the wrist- joint tend to point on the dorsal aspect, 

 to the radial or ulnar side of the tendon of the extensor quinti 

 digiti proprius. An incision immediately to the ulnar side of 

 the tendon of the extensor carpi ulnaris affords the best drainage 

 when the forearm is subsequently placed in the mid -prone 

 position. 



In extensive tuberculous disease the Dorso-Ulnar Incision 

 (Kocher) offers the best approach, and little damage is done to 

 the tendons if the subperiosteal or the subcortical method is 



