The Forearm. 83 



attached to it, while the lower fragment is drawn for- 

 wards by the biceps and inwards by the pronator radii 

 teres. The biceps cannot draw it forward to any great 

 extent, since the supinator brevis would tend to prevent 

 such displacement, nor, is the lower fragment materially 

 rotated since the supinating action of the biceps, and of 

 that part of the supinator brevis attached, is about neut- 

 ralized by the pronating power of the pronator radii teres. 



Fracture of the shaft between the biceps and the pro- 

 nator radii teres. In this fracture the upper fragment is 

 flexed by the biceps and supinated by the combined action 

 of this muscle and of the supinator brevis, whereas the 

 lower fragment is drawn inwards towards the ulna and 

 pronated by the pronator radii teres and pronator quad- 

 ratus. The knowledge of the actions of these muscles is 

 of importance in the treatment of this fracture, for, were 

 the forearm put up in the usual manner, i.e., in a position 

 midway between supination and pronation, the union that 

 would result would seriously interfere with the future 

 usefulness of the limb, since the upper fragment, already 

 supinated by the biceps, would be too short to be influ- 

 enced by the splints and if the arm were put up in the 

 position referred to, the splints would partially pronate 

 the lower fragment, hence, a partially pronated lower 

 fragment would be united to a supinated upper fragment 

 with the result that when union occurred the power of 

 supination would be materially lessened. 



The proper method of treating this fracture would be 

 to put it up with superior and inferior splints, rather than 

 with interns 1 and external ones, because, since it is im- 

 possible to control the upper fragment by means of splints 

 it being too short, and, since the upper fragment is supi- 

 nated, it will be necessary to bring the lower fragment 

 into a position of supination also, so that the supinated 



