256 SI'KGICAL APPLIED ANATOMY. [Chap, xiv, 



the two opposed forces represented by the biceps and 

 brachialis anticus above and the weight of the loaded 

 shovel in the hand below. When both bones are 

 broken and the fractures are oblique, shortening may 

 be produced by the united action of the flexors and 

 extensors. The displacement varies greatly, and de- 

 pends rather upon the direction of the violence than 

 upon muscular action. Thus Hamilton says : " I have 

 seen the fragments deviate slightly in almost every 

 direction." If union be delayed, the delay is usually 

 in the radius, since it is the more mobile of the two 

 bones. When the radius alone is broken (1) between 

 the insertions of the biceps and pronator teres, the 

 upper fragment is flexed by the biceps and fully 

 supinated by that muscle and the small supinator. 

 The lower fragment will be pronated by the two pro- 

 nators, and drawn in towards the ulna by means 

 of those muscles. If such a fracture be put up 

 with the hand midway between the prone and supine 

 position, the following evils result : the upper frag- 

 ment is fully supinated by the muscles ; the lower 

 fragment is placed in the mid-position by the splints. 

 It follows that the proper axis of the bone is not repro- 

 duced, and the use of the biceps and supinator brevis 

 as supinators is entirely lost. Thus patients so treated 

 usually recover with great loss in the power of 

 supination ; and to avoid this ill result, it is advised 

 to put the limb up in full supination, so that the two 

 fragments may unite in their proper axis, the upper 

 fragment being supinated by the muscles, the lower 

 by the splints. (2) When the fracture is between the 

 insertions of the two pronators, the upper fragment 

 may be carried a little forwards by the biceps and pro- 

 nator teres, and drawn towards the ulna by the latter 

 muscle. The bone will probably be in the mid-position, 

 the two supinators (biceps and supinator brevis) 

 attached to the fragment being more or loss 



