Shoulder Girdle Blood Supply Basins
To understand the pathways of collateral blood flow, one must clearly visualize the list of key vessels supplying the scapular region and shoulder joint. Branches of two major trunks meet in this zone: the subclavian artery (a. subclavia) and the axillary artery (a. axillaris).
The subclavian artery system gives rise to the thyrocervical trunk (truncus thyrocervicalis), which gives off the suprascapular artery (a. suprascapularis), as well as the transverse cervical artery (a. transversa colli) with its deep branch (ramus profundus a. transversae colli).
The axillary artery, which provides the primary blood supply to the upper extremity, gives off the large subscapular artery (a. subscapularis). It gives rise to the circumflex scapular artery (a. circumflexa scapulae) and the thoracodorsal artery (a. thoracodorsalis). In addition, the anterior and posterior circumflex humeral arteries (a. circumflexa humeri anterior et posterior) and the thoracoacromial artery (a. thoracoacromialis) branch directly from the axillary artery.
Distal to the axillary region, blood flow continues into the brachial artery (a. brachialis), a branch of which is the deep brachial artery (a. profunda brachii), giving off the deltoid branch (ramus deltoideus).
Scapular Arterial Circle
Scapular network (Rete scapulare) is a vital anastomotic node located in the infraspinous tissue and directly within the thickness of the infraspinatus muscle. This collateral circle is formed by the joining of branches from three vessels originating from different main arterial basins:
- Suprascapular artery (a. suprascapularis) is a branch of the thyrocervical trunk, which originates from the subclavian artery.
- Deep branch of the transverse cervical artery (ramus profundus a. transversae colli) also originates from the subclavian artery system.
- Circumflex scapular artery (a. circumflexa scapulae) is a branch of the subscapular artery, which in turn branches off the axillary artery.
Multiple connections between these three arteries in the infraspinous fossa create a reliable bypass pathway when main blood flow is disrupted.
Hemodynamics in Axillary Artery Occlusion
The clinical significance of the scapular circle is most evident when blood flow through the main axillary artery (a. axillaris) is hindered or completely blocked. A critically important condition for successful compensation is the level of occlusion: the blockage must be located proximally (above) the origin of its main collateral trunk from the axillary artery — the subscapular artery (a. subscapularis).
In this situation, the blood supply to the entire upper extremity is preserved through shunting via the scapular circle. The pathway of collateral blood flow is as follows:
- Blood from the subclavian artery system is directed through its branches: the suprascapular artery and the transverse cervical artery.
- Through these vessels, a powerful blood flow reaches the infraspinous fossa.
- Through a ramified network of anastomoses, blood flows into the circumflex scapular artery.
- Next, retrograde flow occurs: blood moves against its normal direction through the circumflex scapular artery and enters the subscapular artery.
- From the subscapular artery, the blood volume flows back into the axillary artery, but distally (below) the site of occlusion.
- After this, blood flow naturally distributes to all arteries of the upper extremity, preventing severe tissue ischemia.
Acromiadeltoid Network
The second important collateral system of the shoulder girdle is the acromiadeltoid network (Rete acromiale). It is formed by anastomoses of vessels supplying the shoulder joint and the deltoid muscle.
This functional network comprises:
- The acromial branch arising from the thoracoacromial artery (a. thoracoacromialis).
- The deltoid branch, also originating from the thoracoacromial artery.
- Both circumflex humeral arteries (anterior and posterior — a. circumflexa humeri anterior et posterior).
These blood vessels actively interact with each other, forming an additional collateral bed that contributes to the adequate blood supply of the articular complex and the surrounding muscle mass.
Briefly: answers to topical questions
Which arteries participate in the formation of the acromiadeltoid network (rete acromiale)?
The formation of the acromiadeltoid network involves:
- Acromial branch (r. acromialis) of the thoracoacromial artery (a. thoracoacromialis).
- Deltoid branch (r. deltoideus) of the thoracoacromial artery (a. thoracoacromialis).
- Anterior and posterior circumflex humeral arteries (aa. circumflexae humeri anterior et posterior).
Which branches arise from the thyrocervical trunk?
The thyrocervical trunk (truncus thyrocervicalis) usually gives off four branches.
- Inferior thyroid artery (a. thyroidea inferior) ascends to the level of the sixth cervical vertebra and supplies the thyroid gland.
- Superficial cervical artery (a. cervicalis superficialis).
- Ascending cervical artery (a. cervicalis ascendens).
- Suprascapular artery (a. suprascapularis) participates in the formation of the scapular arterial collateral circle.
Which arteries are direct branches of the axillary artery?
The direct branches of the axillary artery (a. axillaris) in its various segments are the following vessels:
- Superior thoracic artery (a. thoracica superior) — branches off in the clavipectoral triangle.
- Thoracoacromial artery (a. thoracoacromialis) — branches off in the clavipectoral triangle.
- Lateral thoracic artery (a. thoracica lateralis) — branches off in the pectoral triangle.
- Subscapular artery (a. subscapularis) — the largest branch, originating on the posterior wall.
- Anterior and posterior circumflex humeral arteries (aa. circumflexae humeri anterior et posterior) — originate on the posterior wall.
With which vessels does the thoracodorsal artery anastomose?
The thoracodorsal artery (a. thoracodorsalis) forms anastomoses with branches of the transverse cervical artery.
- Transverse cervical artery (a. transversa cervicis) — its branches connect with the thoracodorsal artery in the area of the back muscles.
The thoracodorsal artery itself is the terminal branch of the subscapular artery, descends along the lateral border of the scapula, and acts as the main vessel supplying the latissimus dorsi muscle.
Through which topographic opening does the circumflex scapular artery pass to the posterior surface of the scapula?
The circumflex scapular artery (a. circumflexa scapulae) passes to the posterior surface of the scapula through the triangular space (foramen trilaterum).
- Triangular space (foramen trilaterum) is located on the posterior wall of the axillary fossa, medial to the quadrangular space.
Having passed through this opening from the axillary region into the scapular region, the artery pierces the fascial sheath of the teres minor muscle, curves around the lateral border of the scapula, and branches within the muscles of the infraspinous fossa, participating in the formation of the scapular arterial circle.
Class and exam questions
Which arteries form the scapular collateral circle?
Three main vessels participate in the formation of the scapular circle: the suprascapular artery (a. suprascapularis), the deep branch of the transverse cervical artery (ramus profundus a. transversae colli), and the circumflex scapular artery (a. circumflexa scapulae). The first two belong to the subclavian artery basin, and the third belongs to the axillary artery basin.
Where exactly are the anastomoses of the scapular network located?
The anastomoses of the scapular arterial circle are localized in the infraspinous fossa. They run directly in the loose infraspinous tissue and are also densely distributed within the thickness of the infraspinatus muscle itself.
At what level of occlusion is the scapular circle able to compensate blood flow?
Adequate compensation of upper limb circulation is possible only if the occlusion of the axillary artery occurs proximally (above) the origin of the subscapular artery.
What does retrograde blood flow in the scapular circle mean?
Retrograde flow is the movement of blood in a direction opposite to normal physiology. During occlusion, blood flows from the circumflex scapular artery back into the subscapular artery to re-enter the main trunk distal to the site of blockade.
What else to study on this topic
- Topography and branches of the thoracodorsal artery (a. thoracodorsalis)
- Blood supply to the shoulder joint and the role of the humeral circumflex arteries
- Branches of the deep brachial artery (a. profunda brachii) and the deltoid branch
- Topographic landmarks and surgical approaches for ligation of the axillary artery
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