PRACTICAL CONSIDERATIONS : THE RADIUS. 



293 



Development. — The centre for the shaft appears at the end of the second 

 month, and forms the whole bone, except the lower end and the head. The nucleus 

 for the former appears at the end of the second year and that for the head at the 



Fig. 307. 



B C 



Ossification of radius. Ay at birth ; B, at two years ; C, at five years ; D, between eighteen and nineteen years. 

 a, centre for shaft ; b, for lower epiphysis ; c, for upper epiphysis. 



end of the fifth. The latter unites at about fifteen, the lower at eighteen or nineteen. 

 A scale-like epiphysis for the bicipital tuberosity is said to appear towards eighteen 

 and to fuse very promptly. 



PRACTICAL CONSIDERATIONS. 



The radius may be absent or more or less defective, and in either case there is 

 apt to be corresponding absence or deficiency in the hand (Humphry). 



As might be expected, injuries of the upper end in the adult are extremely 

 rare. Except at one point (just below the external condyle posteriorly), the head 

 is far from the surface and deeply buried beneath the thick supinators and the long 

 and short radial extensors of the carpus. Even at that point, more prominent bony 

 processes — the external condyle and the olecranon — receive the brunt of the injury 

 in cases of falls or blows. 



The upper epiphysis does not become fully ossified until the fifteenth year, and ' 

 is united to the diaphysis at the beginning of the sixteenth year. It is, therefore, 

 among the last of the epiphyses of the long bones to ossify and the first to join its 

 diaphysis. The violence which separates it from the shaft is often direct. In cases 

 of indirect violence the force is applied usually as a combined pull and twist on the 

 forearm of a very young child. As the epiphysis is altogether intra-articular (the 

 synovial membrane lining the whole inner surface of the orbicular ligament), swelling 

 is early and marked. As there is direct communication with the larger synovial 

 cavities of the elbow, the whole joint will participate in the effusion. 



Although no ligaments or tendons are attached to the epiphysis, the orbicular 

 ligament hugs it closely and holds it in place. If any displacement occurs, the 

 upper part of the diaphysis may go either forward or backward. On movements of 

 pronation and supination, the epiphysis can be felt immovable just below the external 

 condyle. 



An injury known as "elbow-sprain," or "pulled elbow," and described as a 

 "subluxation of the orbicular ligament" and as a "subluxation of the head of the 

 radius," should be mentioned here because, although it has been known for more 

 than two hundred years, has well-defined and constant symptoms, occurs in one 



