328 APPLIED ANATOMY. 



OPERATIONS ON THE BONES AND OTHER STRUCTURES OF THE 



FOREARM. 



The forearm may require to be operated on for disease or injuries of the bones, 

 tumors, foreign bodies, wounds, etc. In operating on this region of the body it is to 

 be constantly borne in mind that it contains a multitude of structures each of which 

 is essential to the proper performance of some special function. Injury to these 

 structures is followed by a corresponding functional disability. Attempts at brilliant 

 operating are out of place and the surgeon should be exact, careful, and even tender 

 in his handling of the various structures. 



The forearm is mainly nourished by the volar and dorsal interosseous arteries ; the 

 radial and ulnar pass through it to nourish the hand. These latter are to be avoided. 



The nerves that supply the forearm are given off high up near the elbow, hence 

 they are, not usually in danger of injury. The median, ulnar, and superficial branch 

 of the radial nerve pass to the hand and they, if possible, are to be avoided. 



It is therefore evident that as far as the arteries and nerves are concerned oper- 

 ations in the lower part of the forearm are less dangerous than those in the upper. 

 With the muscles it is just the opposite. In the lower half the muscles become ten- 

 dinous and soon form groups or masses of tendons. These tendons are separated by 

 thin connective-tissue sheaths or synovial membrane which allow them to move freely 

 as the muscles contract. Any interference with these sheaths or their contents 

 causes an outpouring of inflammatory material that binds them together and fetters 

 their action. As healing takes place contraction sets in and the patient is left with a 

 useless claw-like hand. For these reasons large incisions and displacements and 

 interference with tendons are to be avoided whenever possible. 



As the muscles mostly run longitudinally the incisions should also be longitu- 

 dinal. Division of the superficial veins is not liable to cause trouble, but the large 

 radial, median, or ulnar veins on the anterior surface may be plainly visible and then 

 the incision should be made so as to avoid wounding them. 



The only superficial nerve to be so avoided is the superficial branch of the 

 radial. It is alongside of the radial artery in its middle third, but about 7 or 8 cm. 

 (3 in.) above the wrist it leaves the artery and winds under the brachioradialis to go 

 down the outer and posterior surface of the radius. It is here to be looked for and 

 avoided, as it furnishes sensation to the thumb, index, middle, and half of the ring 

 fingers. 



If it is desired to penetrate the muscles their direction is to be remembered. 

 The superficial flexor muscles arise from the internal condyle, hence the incision 

 should point upward toward it. The direction of the pronator radii teres is from 

 the internal condyle to the middle of the radius. The deep flexors are parallel with 

 the bones. 



Posteriorly the extensor group of muscles tends toward the external condyle. 

 A third group on the radial side comprises the brachioradialis and the extensor carpi 

 radialis longior and brevior. The tendon of the first lies on the outer surface of the 

 radius with the other two immediately posterior to it. Crossing the posterior and 

 outer surface of the radius in its lower third are the extensor ossis metacarpi pollicis 

 and extensor brevis pollicis tendons. 



If it is desired to reach the bones the ulna can be exposed posteriorly where it 

 is subcutaneous in its entire length by an incision between the flexor carpi ulnaris 

 and extensor carpi ulnaris. The deep fascia is attached to the bone at this point. 



If it is desired to expose the radius, H. Morris {Clin. Soc. Trans., vol. x, p. 138) 

 has advised going in between the brachioradialis and the extensor carpi radialis 

 longior. He used the superficial branch of the radial nerve as a guide to the desired 

 interspace. 



If an incision were made upward from the outer surface of the styloid process of 

 the radius one would first encounter the tendons of the extensor brevis pollicis and 

 extensor ossis metacarpi pollicis muscles. These being displaced posteriorly would 

 reveal the brachioradialis tendon crossing from beneath the posterior border of the 

 radius; 5 to 7 cm. (2 to 3 in.) above the styloid process would be the superficial 



