THE FOREARM AND WRIST 69 



fragment into line with it by flexing the elbow and supinating 

 the hand. 



In Fractures immediately Distal to the Insertion of the 

 Pronator Teres, the proximal fragment is pronated and slightly 

 flexed. The supinating action of the biceps is counteracted 

 by the pronator teres, which acts at a greater mechanical 

 advantage. The distal fragment is pronated by the pronator 

 quadratus, and its proximal end is tilted towards the ulna as 

 in the previous fracture. In this case the proximal fragment 

 is long enough to be controlled,, and the forearm is put up in the 

 mid-prone position, since the distance between the ulna and 

 radius is normally greatest in this position. Dinar flexion of 

 the hand helps to tilt the proximal end of the distal fragment 

 away from the ulna. 



The Superficial Muscles of the Forearm. The Flexor carpiradialis and 

 Palmaris longus both become tendinous about the middle of the forearm. 

 The palmaris longus tendon is rather longer and considerably narrower 

 than that of the flexor carpi radialis. Both muscles, when acting with 

 their groups, are powerful flexors of the wrist and weak flexors of the 

 elbow. When the flexor carpi radialis acts alone, it produces flexion and 

 radial deviation at the wrist ; when it acts along with the radial extensors, 

 radial deviation alone takes place. 



The Flexor digitorum sublimis (p. 84) lies deep to the preceding tendons 

 and partly to their ulnar side. The individual tendons arise in the distal 

 third of the forearm, and pass behind the transverse carpal (anterior annular) 

 ligament. It is primarily a flexor of the proximal inter-phalangeal joints, 

 and secondarily a flexor of the metacarpo-phalangeal, wrist, and elbow- 

 joints. 



The Flexor carpi ulnaris (p. 67) is the most medially placed muscle of this 

 group, and is supplied by the ulnar nerve (C. 8 and T. i). When acting 

 with its group, it helps to flex the wrist and elbow joints, but, when acting 

 with the extensor carpi ulnaris, it produces ulnar deviation of the hand. 



Ulnar Nerve. The course of the Ulnar Nerve may be 

 indicated by drawing a line from the medial epicondyle to 

 the lateral margin of the pisiform. In the proximal part of the 

 forearm the nerve is almost subcutaneous and may be rolled 

 to and fro against the ulna. It can be exposed by a vertical 

 incision through the skin and fascia behind the medial epicondyle, 

 and is found in contact with the medial side of the elbow-joint. 



As the result of sudden violent flexion of the elbow, the deep 

 fascia over it is sometimes torn and the ulnar nerve slips forwards 

 round the medial epicondyle. This dislocation of the nerve 

 may require operative interference. 



After supplying the joint, the ulnar nerve passes between 

 the two heads of the flexor carpi ulnaris and almost immediately 

 gives off branches to supply that muscle and the medial part of 



