PRACTICAL CONSIDERATIONS : MUSCLES AND FASCIA. 589 



2. Anconeus (Fig. 581). 



Attachments. — The anconeus is a short muscle which arises from the posterior 

 surface of the external condyle of the humerus. Its fibres diverge to form a triangu- 

 lar sheet which is i7iserted into the upper part of the posterior surface of the ulna and 

 into the outer surface of the olecranon process. 



Nerve-Supply. — By the musculo-spiral nerve from the seventh and eighth 

 cervical nerves. 



Action. — To assist the triceps in extending the arm. 



PRACTICAL CONSIDERATIONS : MUSCLES AND FASCIA OF THE 



ARM. 



The deep fascia of the arm, continuous above with that over the deltoid and with 

 the clavi-pectoral fascia, closely embraces all the muscular structures and resists the 

 outward passage of subfascial collections of blood or pus, which therefore, under the 

 influence of gravity, tend for a time to follow the intermuscular spaces downward. 

 CEdema and swelling above the elbow are thus not uncommon as a result of disease 

 or injury at a higher level. Blood or pus may reach the surface by following the 

 structures that pierce the fascia, — viz., the basilic vein and the internal and external 

 cutaneous nerves. The ecchymosis after fracture sometimes takes this course. The 

 intermuscular septa (page 585) divide the space enclosed by the brachial aponeurosis 

 into an anterior and a posterior compartment extending from the level of the deltoid 

 and coraco-brachialis insertions to that of the two condyles. They, too, have some 

 effect in limiting effusions, but the latter, especially if due to infection, can readily 

 pass from one space to the other by following the musculo-spiral nerve or the superior 

 profunda artery through the outer septum, or the ulnar nerve, inferior profunda artery, 

 or anastomotica magna through the inner septum. 



In selecting a method of amputation through the arm it should be remembered 

 that above the middle most of the muscles that it would be necessary to divide are 

 free to retract, — i.e., the deltoid, the long head of the triceps, the coraco-brachialis, 

 and the biceps. Below the middle the biceps is the only muscle unattached. In 

 the former situation, therefore, the circular method is apt to lead to a " conical 

 stump' ' from the too free retraction of the flaps and from the activity of the upper 

 humeral epiphysis (page 272). In amputation just above the elbow the circular 

 method is applicable, but the incision should be a little lower at the antero-internal 

 aspect of the limb to allow for the greater retraction in the bicipital region. 



Inward dislocation of the tendon of the long head of the biceps muscle has 

 probably occurred from direct violence as an uncomplicated lesion in a few cases. 

 The symptoms are said to be (White) : (<?) the recognition of the bicipital groove 

 empty ; (^) inward rotation due to the pressure of the tendon on the lesser tuberosity 

 and on the tendon of the subscapularis ; (<:) adduction of the humeral head, leaving 

 a slight depression beneath the tip of the acromion ; (af) obvious tension along the 

 inner edge of the biceps muscle when the forearm is extended ; (<?) diminution in the 

 vertical circumference of the shoulder ; and (/") shortening of the distance between 

 the acromion and external condyle ; both of the last two symptoms are due to the 

 elevation of the humeral head under the influence of the deltoid, the sup.raspinatus, 

 and the clavicular fibres of the pectoralis major, that of the biceps tendon being with- 

 drawn. These and other symptoms of this lesion (although it is extremely rare) 

 should be studied in connection with the anatomy of the muscles involved, as an aid 

 in elucidating their action.^ 



Rupture of the biceps tendon has always been caused by violent muscular action, 

 and is usually accompanied either by the sudden appearance of a more or less firm 

 tumor on the front of the arm or by complete relaxation and fiabbiness of the whole 

 muscle. The symptoms mentioned as characteristic of dislocation of the tendon 

 have not been noted in any recorded case of rupture, with the exception of those due 

 to the elevation of the head of the humerus. 



^ J. William White : American Journal of the Medical Sciences, January, 1884. 



