The circulatory system in the upper limb is a highly organized network of arteries and veins that supply muscles, bones, and soft tissues with essential nutrients and oxygen. One of the key vessels in this region is thevasa circumflexa humeri posterior, also known as the posterior circumflex humeral artery. This artery plays an important role in maintaining blood flow to the shoulder joint and surrounding muscles, particularly the deltoid. Understanding the anatomy, origin, course, and clinical significance of this artery is essential for students, clinicians, and professionals working in the fields of anatomy, orthopedics, and surgery.
Overview of the Posterior Circumflex Humeral Artery
Definition and Terminology
The posterior circumflex humeral artery is a branch of the axillary artery. It is paired with the anterior circumflex humeral artery, and together they form an arterial circle around the surgical neck of the humerus. The Latin name,vasa circumflexa humeri posterior, reflects its circular path and anatomical location around the humerus.
Origin of the Artery
This artery typically originates from the third part of the axillary artery, which is the segment located distal to the pectoralis minor muscle. The axillary artery itself is a continuation of the subclavian artery and becomes the brachial artery after passing the lower border of the teres major muscle.
Course and Distribution
Anatomical Pathway
After originating from the axillary artery, the posterior circumflex humeral artery passes posteriorly through the quadrangular space. This space is defined by the following boundaries:
- Superiorly: Teres minor muscle
- Inferiorly: Teres major muscle
- Medially: Long head of the triceps brachii
- Laterally: Surgical neck of the humerus
Alongside this artery travels the axillary nerve, which also passes through the quadrangular space. Once it emerges from this space, the artery winds around the surgical neck of the humerus and enters the deltoid region.
Structures Supplied
The posterior circumflex humeral artery provides branches that supply the following structures:
- Deltoid muscle
- Teres major and teres minor muscles
- Long head of the triceps brachii
- Glenohumeral (shoulder) joint
- Skin overlying the deltoid area
It forms anastomoses with the anterior circumflex humeral artery and other nearby arteries, contributing to the collateral circulation of the shoulder region. This collateral supply is essential in case of arterial occlusion or trauma.
Relation to Surrounding Structures
Axillary Nerve
One of the most important anatomical relationships of the posterior circumflex humeral artery is with the axillary nerve. Both structures pass through the quadrangular space and are closely associated throughout their course. Injury or compression in this area can affect both the artery and the nerve, leading to clinical symptoms such as deltoid weakness or impaired shoulder movement.
Quadrangular Space Syndrome
This syndrome occurs when the structures passing through the quadrangular space, including the posterior circumflex humeral artery and the axillary nerve, become compressed. Causes may include trauma, hypertrophy of nearby muscles, or fibrous bands. Symptoms typically include posterior shoulder pain, weakness in shoulder abduction, and, in some cases, diminished blood flow to the upper limb.
Clinical Relevance
Injury and Trauma
Fractures involving the surgical neck of the humerus can endanger the posterior circumflex humeral artery. Due to its close relationship with the bone, a fracture can lead to arterial rupture or hematoma formation, which may compromise blood supply to the shoulder or result in neurovascular damage.
Surgical Considerations
During surgical procedures involving the shoulder, such as open reduction of fractures, shoulder arthroscopy, or muscle repair, knowledge of the artery’s location is vital. Surgeons must avoid damaging this artery to prevent excessive bleeding or complications involving the axillary nerve.
Imaging and Diagnosis
Advanced imaging techniques such as MRI, CT angiography, and Doppler ultrasound can visualize the posterior circumflex humeral artery. These methods are useful in diagnosing vascular compression, aneurysms, or damage following trauma.
Comparison with the Anterior Circumflex Humeral Artery
Path and Distribution
While both arteries arise from the axillary artery and contribute to the arterial network around the humerus, there are notable differences:
- The posterior circumflex humeral artery is usually larger in diameter than the anterior counterpart.
- The anterior circumflex artery passes anteriorly around the humerus, while the posterior circumflex artery goes through the quadrangular space to reach the posterior region.
- The anterior branch primarily supplies the anterior portion of the shoulder joint and surrounding soft tissues, while the posterior artery is more responsible for the deltoid and posterior structures.
Clinical Implications
Because of its size and deeper location, the posterior circumflex humeral artery is less likely to be injured during superficial trauma but may be more susceptible to complications in shoulder dislocation or proximal humerus fractures.
Anatomical Variations
Variations in Origin
Although the posterior circumflex humeral artery typically arises from the third part of the axillary artery, anatomical variations may occur. In some individuals, it may branch off more proximally or share a common trunk with the anterior circumflex humeral artery or the subscapular artery.
Implications of Variation
Understanding these variations is important for vascular surgeons, radiologists, and clinicians performing invasive procedures in the shoulder area. Misidentification can lead to ineffective treatment or surgical complications.
Importance in Collateral Circulation
Maintaining Blood Flow
The shoulder region has a rich network of arteries that ensures blood supply even in the presence of occlusions or vascular injury. The posterior circumflex humeral artery contributes to this network by anastomosing with other arteries, including:
- Anterior circumflex humeral artery
- Subscapular artery
- Suprascapular artery
- Thoracoacromial artery
This extensive anastomotic system helps maintain tissue perfusion and is particularly vital in cases where the axillary artery is compromised.
Thevasa circumflexa humeri posterior, or posterior circumflex humeral artery, is a significant vascular structure in the upper limb. Originating from the axillary artery, it supplies the deltoid muscle, shoulder joint, and surrounding soft tissues. Its anatomical relationship with the axillary nerve and its passage through the quadrangular space make it clinically important, particularly in trauma, surgical procedures, and diagnostic imaging. Understanding its course, variations, and functions is essential for health professionals, contributing to safer practices and improved patient outcomes in orthopedic and vascular medicine.