Relations

Posteriorly the third portion of the axillary artery lies on the sub-scapularis, the latissimus dorsi, and teres major muscles, with the musculospiral and circumflex (axillary) nerves between the muscles and the artery.

Anteriorly it is covered by the skin and fascia, the pectoralis major above, and deep fascia of the arm below. The inner root of the median nerve crosses it and sometimes the outer vena comes.

Externally is the coracobrachial muscle (which partly overlaps it and forms its guide), the main trunk and outer head of the median, and the musculocutaneous nerves.

Internally is the axillary vein with the ulnar nerve between it and the artery.

The internal and lesser internal cutaneous nerves also lie to its inner side with the former the more anterior.

Ligation Of The Third Portion Of The Axillary Artery

The arm being placed out from the body, palm upward, the incision for ligating the axillary artery in the third portion of its course is laid along the inner border of the coracobrachial muscle, at about the junction of the anterior and middle thirds of the axilla and on a line joining the middle of the clavicle and a point at the bend of the elbow midway between the two condyles of the humerus.

The middle of the incision should be just above the lower edge of the folds of the axilla. The deep fascia having been opened, the coracobrachial muscle with the musculocutaneous nerve piercing it is pulled outward. Lying on the artery to its outer side is the median nerve; it is to be drawn outward. To the inner side lies the axillary vein with the ulnar nerve beneath it and the internal cutaneous nerve (cutaneus antebrachii medialis) in front of it close to the artery.

The needle is passed from within outward. The artery at this point may be crossed by some muscular fibres coming from the latissimus dorsi and crossing the axilla. The axillary vein is the continuation of the basilic from the lower border of the teres major upward.

Of the two venae comites of the brachial artery the inner one blends with the basilic at the lower border of the teres major; the outer one crosses the artery to empty into the axillary vein on the opposite side.

The axillary vein receives the subscapular, circumflex, long thoracic, acromiothoracic, alar, and cephalic, and contains a pair of valves opposite the lower border of the subscapularis muscle. Collateral Circulation after Ligature of the Axillary Artery. - If the first portion of the axillary is tied, the acromiothoracic artery comes off so low down (under the edge of the pectoralis minor muscle almost) that the ligature is placed above it, in which case the collateral circulation is similar to that of the subclavian (see page 149). The second portion of the axillary, lying beneath the pectoralis minor, is not subject to ligation. • In the third portion the subscapular and anterior and posterior circumflex arteries come off so close together that the ligature will be placed either just below or just above them (Fig. 274).

If below, then the collateral circulation will be between them above and the superior profunda below. If above the subscapular, then the anastomosis would be as follows:

Fig. 274.   Collateral circulation after ligation of the third portion of the axillary artery.

Fig. 274. - Collateral circulation after ligation of the third portion of the axillary artery.

Proximal Vessels.

Distal Vessels.

Acromiothoracic, acromial branch.....

with anterior and posterior circumflex

Acromiothoracic, humeral branch......

with anterior and posterior circumflex

Acromiothoracic, pectoral branch......

with subscapular

Long thoracic branch...............

with subscapular

Alar thoracic branch.................

with subscapular

Posterior scapular (branch of trans, cervical)

with subscapular and dorsalis scapulae

Suprascapular..........................

with dorsalis scapulae and posterior circumflex