VASCULAR ANATOMY OF SHOULDER
The blood supply to the upper extremity is derived from the subclavian artery,
which travels with the brachial plexus between the anterior and middle scalene
muscles. The first important branch relevant to shoulder anatomy is the
thyrocervical trunk, which gives rise to the transverse cervical and
suprascapular arteries. The next branch encountered is the dorsal scapular
artery, which occasionally comes off the transverse cervical artery, as opposed
to the subclavian artery.
The axillary artery is the continuation of the subclavian artery beyond
the lateral border of the first rib. The artery is divided into three sections
based on the position of the pectoralis minor tendon. The first division is
proximal to the tendon and has only one branch, the superior thoracic. It
descends behind the axillary vein to the intercostal muscles of the first and
second intercostal spaces and to the upper portion of the serratus anterior
muscle. The second division is deep to the tendon and has two branches, the
thoracoacromial artery and the lateral thoracic artery. The thoracoacromial
branch gives off four branches: acromial, deltoid, pectoral, and clavicular.
The acromial branch passes lateralward across the coracoid process to the
acromion. It gives branches to the deltoid muscle and participates with
branches of the anterior and posterior circumflex humeral and suprascapular vessels in the formation of the acromial
network of small vessels on the surface of the acromion. The deltoid branch
(often arising not separately but as a branch of the acromial artery) occupies
the interval between the deltoid and pectoralis major muscles in company with
the cephalic vein. It sends branches into these muscles. The pectoral branch is
large and descends between the pectoralis major and minor muscles. It gives
branches to these muscles, anastomoses
with intercostal and lateral thoracic arteries, and, in the female, supplies
the mammary gland in its deep aspect. The clavicular branch is a slender vessel
ascending medialward to supply the subclavius muscle and the sternoclavicular
joint. The lateral thoracic artery is variable. It may arise directly from the
axillary artery, from the thoracoacromial artery, or from the subscapular
artery; it is frequently represented by several vessels. Typically (in 65% of
cases), it arises from the axillary
artery, descends along the lateral border of the pectoralis minor muscle, and
sends branches to the serratus anterior and pectoral muscles and axillary lymph
nodes.
The third division of the axillary artery is distal to the pectoralis
minor tendon and gives off three branches: the subscapular, anterior humeral
circumflex, and posterior humeral circumflex arteries. The sub- scapular artery
is the largest branch of the axillary artery. It divides into the circumflex
scapular and thoracodorsal branches. The circumflex scapular artery, the larger
branch, passes posteriorly through the triangular space, turns onto the dorsum
of the scapula, and ramifies in the infraspinatous fossa. Here, it supplies the
muscles of the dorsum of the scapula and anastomoses with the dorsal scapular artery
and the terminals of the suprascapular artery. By branches given off in the
triangular space, it supplies the subscapularis and the two teres muscles. The
thoracodorsal artery is the principal supply of the latissimus dorsi muscle,
entering it on its deep surface in company with the thoracodorsal nerve. It
frequently has a thoracic branch that substitutes for the inferior portion of
the distribution of the lateral thoracic
artery.
The two circumflex humeral arteries branch next. The anterior vessel gives
off an ascending branch that continues to become the arcuate artery. This
vessel provides the majority of the blood supply to the humeral head. The
posterior circumflex artery passes posteriorly with the axillary nerve through
the quadrangular space. It encircles the surgical neck of the humerus and anastomoses
with the anterior circumflex humeral artery.
The axillary artery becomes the brachial artery as it crosses the
inferior limit of the axilla at the lower border of the teres major. It enters
the arm accompanied by two brachial veins as well as the median, ulnar, and
radial nerves. The axillary vein is anterior and inferior to the artery in
normal posture but rises and is more completely anterior to the artery when the
arm is abducted.
