288 The Wrist Joint 



Excision of the wrist-joint is very rarely needed ; it maybe per- 

 formed by straight lateral incisions, care being taken not to wound the 

 radial artery. 



In lister's method the incision on the inner side of the joint is 

 made in the ordinary way, from two inches above the ulnar styloid 

 process down to the middle of the fifth metacarpal bone ; but the outer 

 incision is made in the line of the second metacarpal bone, and then 

 along the ulnar side of extensor secundi the oblique tendon of thumb 

 (p. 287). This tendon and the radial artery are carefully raised from 

 the wrist, and the tendons of the carpi radialis longior and brcvior are 

 severed, as is also that of the carpi ulnaris. The flexor and extensor 

 tendons of the fingers are raised, the pisiform and the hook of unci- 

 form being detached ; the trapezium requires a snip from the cutting 

 pliers. The carpal bones, being cleared and separated, are taken out ; 

 the carpal ends of the radius and ulna, and of the metacarpal bones, 

 are laid bare and sawn off. It is evident that this latter part of the 

 programme cannot be carried out unless the tendons of the special 

 wrist-extensors had been previously divided, as they are inserted at 

 the base of the metacarpus ; but, when extracting the trapezium, the 

 tendon of the flexor carpi radialis is raised and saved. Personally, I 

 should not attempt the complicated operation, which I have thus briefly 

 sketched out, without carefully reading it up just before, and I deem it 

 unfortunate that the same indulgence cannot always be extended to 

 the student. 



Much of the movement which apparently takes place at the radio- 

 carpal joint actually occurs in the mid-carpal articulation, the flexor 

 and extensors carpi radialis and extensor carpi ulnaris being inserted 

 into the metacarpal bones so that they may influence the wrist and 

 the transverse carpal joints at once. 



The transverse carpal joint and tbe synovial membranes of 

 the carpus. The lower surfaces of the scaphoid and semi-lunar bones 

 form a socket for the head of the os magnum, which articulates on 

 the outer side of the magnum with the trapezium and trapezoid, and 

 on the inner side with the cuneiform and uncifqrm, as shown in the 

 fig. on p. 286. The two rows of carpal bones are connected by anterior, 

 posterior, and lateral ligaments. 



The transverse carpal joint is lubricated by a synovial membrane 

 which is distinct from that of the radio-carpal articulation ; it sends 

 processes between the bones of the second row which extend also 

 into the articulations of the trapezoid and magnum with the middle 

 metacarpal bones. A special synovial membrane is often found for the 

 joint between the unciform and the fourth and fifth metacarp.ils. 

 There are also separate membranes for the joints between the cunei- 

 form and pisiform, and the trapezium and the first metacarpal bone. 

 (The description here given differs somewhat from that figured on 

 p. 286.) 



