Obturator artery

The obturator artery is a branch of the anterior division of the internal iliac artery, responsible for supplying blood to the muscles and structures in the pelvic region and the medial compartment of the thigh. It is part of the vascular network that nourishes the hip joint, obturator muscles, and other tissues in the pelvic area.

Location

The obturator artery is located in the pelvic region. It typically arises from the anterior division of the internal iliac artery, though in some cases, it can originate from the external iliac artery or the inferior epigastric artery. After its origin, it travels along the lateral pelvic wall, passing through the obturator canal, an opening in the pelvic bone, to enter the thigh. Once it reaches the medial thigh, it divides into anterior and posterior branches, which supply the surrounding muscles, the hip joint, and the obturator externus muscle.

Structure and Anatomy

The obturator artery is an important vessel that supplies blood to the pelvic region, hip joint, and medial compartment of the thigh. It follows a distinct course from its origin in the pelvis to its distribution in the thigh, passing through several key anatomical structures. Below is a detailed description of the anatomy of the obturator artery.

Origin

The obturator artery most commonly originates from the anterior division of the internal iliac artery, one of the major vessels supplying the pelvic organs and lower limb. However, variations in its origin are not uncommon. In some cases, the obturator artery may arise from the external iliac artery or the inferior epigastric artery, a branch of the external iliac artery. This variant is referred to as an aberrant obturator artery, occurring in about 20% of individuals.

Course

Once the obturator artery originates from the internal iliac artery (or in rare cases from the external iliac or inferior epigastric arteries), it travels along the lateral pelvic wall. It follows a curved path, running parallel to the pelvic brim and underneath the obturator fascia, which covers the obturator internus muscle. The artery then passes through the obturator canal, a small opening formed by the obturator membrane and pelvic bones, to exit the pelvis and enter the thigh.

Obturator Canal: The obturator canal is an important passageway through which the obturator artery, vein, and nerve pass. It is located in the superior part of the obturator foramen, a large opening in the pelvic bone.

Branches

After passing through the obturator canal, the obturator artery divides into anterior and posterior branches that supply different regions of the thigh and pelvis.

• Anterior Branch:The anterior branch descends along the anterior surface of the obturator membrane, traveling between the adductor muscles in the medial thigh. It supplies blood to the adductor longus, adductor brevis, gracilis, and pectineus muscles, which are responsible for the movement of the thigh. The anterior branch also contributes to the blood supply of the hip joint by sending small branches to the acetabulum and surrounding structures.
• Posterior Branch:The posterior branch of the obturator artery passes behind the obturator externus muscle, supplying it and the adductor magnus muscle. It also sends a small branch through the acetabular notch, called the acetabular branch, which supplies the ligament of the head of the femur (ligamentum teres). This branch helps provide blood to the head of the femur, contributing to its nourishment and function.

Relations to Other Structures

The obturator artery runs in close proximity to several important anatomical structures in both the pelvic and thigh regions.

• Obturator Nerve and Vein: The obturator artery is accompanied by the obturator nerve and obturator vein as it passes through the obturator canal. These structures run together along the lateral pelvic wall and through the obturator canal, where they continue to supply the medial thigh.
• Pelvic Structures: In the pelvis, the obturator artery runs adjacent to the obturator internus muscle and pelvic fascia. As it travels toward the obturator canal, it is positioned near the pelvic brim and along the lateral pelvic wall, making it an important artery in pelvic anatomy.
• Adductor Muscles: In the thigh, the anterior and posterior branches of the obturator artery run between the muscles of the medial compartment, including the adductor longus, adductor brevis, adductor magnus, and gracilis muscles. These muscles are primarily involved in the adduction and stabilization of the thigh.

Anastomoses

The obturator artery forms important anastomoses (connections) with other arteries, ensuring a rich blood supply to the pelvis and thigh.

• Inferior Epigastric Artery: In cases where the obturator artery originates from the inferior epigastric artery (aberrant obturator artery), it forms an anastomosis with the typical internal iliac-derived obturator artery, ensuring collateral blood flow in the pelvic region.
• Medial Circumflex Femoral Artery: In the thigh, the obturator artery anastomoses with the medial circumflex femoral artery, which also supplies blood to the muscles of the medial thigh and the hip joint.
• Superior and Inferior Gluteal Arteries: In the pelvic region, the obturator artery may also form anastomoses with the superior and inferior gluteal arteries, both of which are branches of the internal iliac artery that supply the gluteal region.

Variations

The obturator artery shows considerable anatomical variability, particularly in its origin and branching patterns.

• Aberrant Obturator Artery: As mentioned, the obturator artery may arise from the external iliac artery or the inferior epigastric artery in some individuals. This variation is important in surgical procedures, as the artery’s course may differ from its typical path along the internal iliac artery.
• Additional Branches: Occasionally, the obturator artery may give rise to additional branches, including those supplying adjacent muscles and the pelvic wall. The size and distribution of these branches can vary between individuals.

Function

The obturator artery plays a crucial role in supplying oxygenated blood to a variety of structures in the pelvic and thigh regions. Below is a detailed description of the functions of the obturator artery.

Blood Supply to the Medial Compartment of the Thigh

One of the primary functions of the obturator artery is to provide blood to the medial compartment of the thigh, which consists of muscles responsible for adducting the thigh (moving the leg toward the midline). These muscles are vital for maintaining balance, stabilizing the hip joint, and facilitating walking and running.

• Adductor Muscles: The anterior branch of the obturator artery supplies the adductor longus, adductor brevis, gracilis, and pectineus muscles. These muscles are involved in thigh adduction and are critical for the stability and movement of the lower limb.
• Adductor Magnus Muscle: The posterior branch of the obturator artery supplies the adductor magnus muscle, the largest muscle in the adductor group, which also helps stabilize the pelvis during walking and standing.

By ensuring the medial thigh muscles are well-vascularized, the obturator artery supports key lower limb movements and the overall function of the hip joint.

Blood Supply to the Hip Joint

Another significant function of the obturator artery is to supply blood to the hip joint, particularly through the acetabular branch of the posterior division. This branch plays an important role in nourishing the structures that support and stabilize the hip joint.

• Acetabular Branch: The acetabular branch of the posterior obturator artery passes through the acetabular notch to supply the ligamentum teres (ligament of the head of the femur). This ligament helps anchor the head of the femur to the acetabulum (hip socket), and the artery provides oxygenated blood to support its function.
• Femoral Head: The acetabular branch indirectly contributes to the blood supply of the head of the femur, a critical region for maintaining the integrity and function of the hip joint. The femoral head relies on a robust blood supply to prevent conditions like avascular necrosis, where a lack of blood flow leads to the death of bone tissue.

By supplying the hip joint, the obturator artery plays an essential role in supporting hip stability, movement, and the overall function of the lower limb.

Blood Supply to the Pelvic Muscles and Structures

The obturator artery also supplies blood to several pelvic muscles and structures, particularly during its course within the pelvis before it enters the obturator canal. Its role in nourishing these pelvic structures is crucial for maintaining their health and functionality.

• Obturator Externus Muscle: The obturator artery provides blood to the obturator externus muscle, which plays a role in laterally rotating the thigh. This muscle is important for stabilizing the head of the femur in the acetabulum, helping maintain hip joint stability during walking and running.
• Pelvic Fascia and Muscles: The artery also contributes to the vascular supply of the pelvic fascia and nearby muscles, including the obturator internus muscle. These structures are involved in the stability and movement of the pelvis and lower limbs.

By supplying the obturator externus muscle and nearby structures, the obturator artery ensures that these muscles remain functional, supporting proper movement and stability in the pelvic region.

Contribution to the Blood Supply of the Femoral Head

In addition to its role in the acetabular branch, the obturator artery also contributes to the overall blood supply of the head of the femur, particularly through its connections with other arteries in the pelvic and thigh regions.

• Acetabular Branch: The acetabular branch of the posterior obturator artery enters the hip joint through the acetabular notch, where it supplies blood to the ligamentum teres. This ligament plays a key role in maintaining the health of the femoral head by supplying blood to the surrounding bone and cartilage.
• Medial Circumflex Femoral Artery Anastomosis: The obturator artery forms an important anastomosis with the medial circumflex femoral artery, which is another significant contributor to the blood supply of the femoral head. These anastomotic connections ensure that the femoral head remains well-vascularized, even if one artery is compromised.

The obturator artery’s role in femoral head vascularization is vital for maintaining joint health, preventing conditions such as avascular necrosis, and ensuring proper hip function.

Contribution to the Pelvic Vascular Network

The obturator artery forms part of a larger vascular network within the pelvis and thigh, contributing to the collateral circulation that supplies various structures. This network helps ensure consistent blood flow, even in cases of injury or blockage to other vessels.

• Anastomosis with Medial Circumflex Femoral Artery: The obturator artery anastomoses with the medial circumflex femoral artery, which supplies the thigh and hip joint. This connection ensures that the muscles of the medial thigh and the hip joint receive sufficient blood supply, even if one artery is compromised.
• Anastomosis with Inferior Epigastric Artery: In cases where the obturator artery originates from the inferior epigastric artery (aberrant obturator artery), it forms an anastomosis with the typical internal iliac-derived obturator artery, ensuring collateral blood flow in the pelvic region.
• Anastomosis with Superior and Inferior Gluteal Arteries: The obturator artery may also form anastomoses with the superior and inferior gluteal arteries, providing additional blood flow to the pelvic region and contributing to the vascularization of the gluteal muscles.

These anastomoses ensure that the obturator artery is part of a well-developed vascular network that supports the pelvic and lower limb regions.

Support for Pelvic Stability and Movement

The obturator artery indirectly supports pelvic stability and lower limb movement by supplying the muscles and joints that contribute to these functions. Its branches ensure that the muscles responsible for adduction and rotation of the thigh, as well as the hip joint, are well-nourished, maintaining proper movement and function.

• Adductor Muscle Support: The artery’s supply to the adductor muscles helps stabilize the pelvis during walking, running, and other weight-bearing activities.
• Hip Joint Stability: The acetabular branch’s contribution to the hip joint supports the movement and stability of the femoral head, essential for proper lower limb function.

Clinical Significance

The obturator artery is clinically significant due to its role in supplying blood to the pelvic region, hip joint, and medial compartment of the thigh. Its proximity to the pelvic brim and obturator canal makes it an important vessel during pelvic surgeries, such as hernia repairs, particularly in cases of obturator hernia, where the artery may be at risk of damage. Injury to the artery during surgery can lead to excessive bleeding and compromised blood flow to the medial thigh muscles and hip joint.

The presence of an aberrant obturator artery (originating from the external iliac or inferior epigastric artery) is a common anatomical variation, occurring in about 20% of individuals. Surgeons need to be aware of this variation during procedures like hernia repairs to avoid inadvertent injury. Additionally, the artery’s role in supplying the femoral head makes it critical in the context of hip surgeries or trauma to the region, where damage to the artery can lead to complications such as avascular necrosis.