326 



APPLIED ANATOMY. 



The carrying angle (page 282) formed by the line of the arm with the line of 

 the forearm, depends on the integrity of the humerus and ulna and their proper 

 articulation. If the ulna is broken high up the forearm is deprived of its support on 

 the inner side and it sags inward, thus approximating the bones, obliterating the 

 interosseous space, and diminishing the carrying angle. In treatment care should 

 be taken that the forearm be not allowed to incline toward the inner side. 



Displacement Posterior. When the displacement is posterior the lower end of 

 the upper fragment is tilted backward by the contraction of the triceps muscle. This 

 causes a marked projection on the back of the forearm below the elbow (Fig. 335). 



In treating this injury the forearm 

 should be placed in at least partial ex- 

 tension (complete extension is usually 

 not necessary) so as to relax the triceps 

 muscle. 



Displacement Anterior. When a 

 person receives a blow in the region of 

 the junction of the upper and middle 

 thirds of the ulna on its posterior sur- 

 face the fragments are pushed forward 

 and an angular deformity is produced, 

 the apex of the angle pointing toward 

 the anterior surface. The force of the 

 blow is not expended entirely on the 

 ulna but, having broken it, continues 

 and pushes or dislocates the radius for- 

 ward (Fig. 336). 



In these injuries the fracture of the 

 ulna is readily recognized, but the dis- 

 location of the head of the radius is often 

 overlooked. If the dislocation is not 

 reduced subsequent flexion of the elbow 

 will not be possible much if any beyond 

 a right angle. The contraction of the 

 biceps not only favors this luxation by 

 pulling the radius forward but tends to 

 cause it to recur after replacement. 



Reduction is to be attempted by 

 supinating and flexing the forearm to 

 relax the biceps and making direct 

 pressure anteroposteriorly on the radius 

 to force the head back into place. The radius may be kept in place by dressing 

 the arm with the elbow in a position of complete flexion. 



FIG. 336. Fracture of the upper third ot the ulna, 

 with anterior angular displacement of the fragments and 

 anterior dislocation of the head of the radius. 



AMPUTATION OF THE FOREARM. 



The lower half of the forearm is so largely tendinous that musculocutaneous 

 flaps are unsuitable ; by the time the tendons are cut short there is little tissue left 

 but skin, superficial and deep fascia, and a few muscular fibres. 



Amputation should be performed as low down as one can so as to save as much 

 as possible. Artificial appliances, so useful in the lower extremity, are, practically, 

 of little value in the upper. The preservation of the power of pronation and supi- 

 nation is to be accomplished when the condition permits. The pronator radii teres 

 has its insertion in the middle of the radius and if the division of the bone is below 

 that point rotary movements will be preserved. 



The surgeon should be acquainted with the position of the main arteries and 

 nerves. Four arteries will require ligation : the radial, ulnar, volar (anterior), and 

 dorsal (posterior) interosseous. Their position as well as that of the nerves will 

 vary accordingly to the site of the amputation. The median and ulnar are the only 

 nerves that require shortening. 



