THE FOREARM AND WRIST 75 



(a) Distal Third. At its proximal end the incision exposes 

 the extensor pollicis brevis and the abductor pollicis longus 

 as they cross the tendons of the radial extensors of the wrist. 

 The extensor digitorum communis is exposed on the ulnar side 

 of the incision and is retracted medially. When the other 

 muscles and tendons mentioned above are retracted laterally,, 

 the distal part of the radius is exposed where it is devoid of 

 muscular attachments. In tuberculous osteo-myelitis the distal 

 part of the diaphysis may then be excised by dividing it proximal 

 to the level of the disease the periosteum having been stripped 

 off and by wrenching it away from the epiphyseal cartilage, 

 which remains attached to the epiphysis. The capsule of the 

 wrist joint is uninjured (Fig. 27). 



(b) Middle Third. The extensor pollicis brevis and the 

 abductor pollicis longus are exposed at the distal end of the 

 wound and are retracted distally and to the ulnar side. The 

 radial extensors of the wrist are retracted laterally, and the 

 bone is exposed between the origin of the abductor longus and 

 the insertion of the pronator teres. 



(c) Head and Proximal Third. When the extensor digitorum 

 communis is separated from the radial extensors of the wrist at 

 this level the supinator is exposed and must be divided below 

 and parallel to the dorsal interosseous nerve (p. 73). In 

 subperiosteal resection of this part of the radius for tuberculous 

 osteo-myelitis, the bone is cut through distal to the level of 

 the disease and the proximal part is wrenched away. The 

 cartilaginous head of the radius, with the epiphysis if it has 

 developed, is wrenched away with the shaft, as it is attached 

 only to the synovial membrane of the elbow-joint and possesses 

 no special ligamentous connections (Fig. 17). In this resection, 

 therefore, the cavity of the elbow-joint is widely opened. 



The Distal Radio-Ulnar Joint. The ulna is excluded 

 from the wrist-joint by a triangular fibro-cartilage the articular 

 disc which is attached by its apex to the base of the styloid 

 process of the ulna and by its base to the medial margin of the 

 distal end of the radius. The capsule is weak and loose, to permit 

 of pronation and supination, and the synovial membrane bulges 

 proximally between the two bones beyond the level of the distal 

 epiphyseal lines. Occasionally the articular disc is perforated, 

 and the synovial membrane becomes continuous with that of 

 the wrist-joint. 



The Radio-Carpal Joint or Wrist- Joint. The proximal 



