Iliolumbar artery

The iliolumbar artery is a branch of the posterior division of the internal iliac artery. It plays a key role in supplying blood to the iliacus and psoas major muscles, as well as parts of the lower spine. The artery arises from the internal iliac artery and quickly divides into two branches: the lumbar and iliac branches, each supplying different anatomical regions.

Location

The iliolumbar artery is located in the pelvic region. It arises from the posterior division of the internal iliac artery, typically just after the internal iliac artery divides into its posterior and anterior divisions. From its origin, the artery ascends behind the psoas major muscle toward the iliac fossa, running near the iliac crest. The lumbar branch travels toward the vertebral column, supplying the lumbar vertebrae and muscles, while the iliac branch extends toward the iliacus muscle on the inner surface of the ilium.

Structure and Anatomy

The iliolumbar artery is an important artery in the pelvic region, providing blood to various muscles and bones of the lower back and pelvis. It originates from the internal iliac artery and divides into two key branches. Below is a detailed description of its anatomy.

Origin

The iliolumbar artery typically arises from the posterior division of the internal iliac artery, which is one of the primary arteries supplying the pelvic organs and structures. The posterior division usually gives rise to three branches: the iliolumbar artery, the lateral sacral arteries, and the superior gluteal artery. The iliolumbar artery is generally the first branch to emerge from this posterior division.

Course

Once it branches from the internal iliac artery, the iliolumbar artery ascends toward the iliac fossa. It runs posterior to the psoas major muscle, a large muscle that plays a role in hip flexion, and lies in close relation to the lumbar vertebrae. As it ascends, the artery travels towards the iliac crest, the curved upper border of the ilium (the largest bone in the pelvis).

Branches

The iliolumbar artery divides into two main branches as it ascends: the lumbar branch and the iliac branch.

Lumbar Branch:

• The lumbar branch ascends medially, running toward the lower lumbar vertebrae. It supplies blood to the psoas major and quadratus lumborum muscles, both of which are important muscles in the lower back. The lumbar branch also provides blood to the lumbar vertebrae, helping to nourish the bones and nearby spinal structures.
• This branch often forms anastomoses (connections) with the lumbar arteries that arise directly from the aorta, contributing to the vascular supply of the lumbar region.

Iliac Branch:

• The iliac branch extends laterally toward the iliac fossa, the concave surface on the inner side of the ilium. It primarily supplies the iliacus muscle, which is involved in hip movement and forms part of the posterior abdominal wall.
• The iliac branch also supplies the ilium, the broad upper part of the pelvic bone, ensuring adequate perfusion to the bone and surrounding tissue.

Relations to Other Structures

• Psoas Major Muscle: The iliolumbar artery runs behind the psoas major, one of the main muscles involved in flexing the hip and lumbar spine. This close proximity makes the artery important in surgical procedures involving the psoas or surrounding structures.
• Lumbar Vertebrae: As the lumbar branch ascends toward the lumbar vertebrae, it provides vascular support to the vertebrae and surrounding ligaments, particularly in the lower spine.
• Iliac Fossa and Ilium: The iliac branch runs through the iliac fossa, a region of the pelvis, where it supplies the iliacus muscle and the ilium. This relationship is significant in providing nourishment to both the bone and muscle structures involved in pelvic movement and support.

Anastomoses

The iliolumbar artery forms several important anastomoses with other arteries in the region:

• Lumbar Arteries: The lumbar branch anastomoses with the lumbar arteries from the abdominal aorta, which also supply the muscles and bones of the lower back. This network of vessels ensures that the lumbar vertebrae and muscles have a consistent blood supply.
• Deep Circumflex Iliac Artery: The iliac branch may also form connections with the deep circumflex iliac artery, which runs along the iliac crest, further contributing to the vascular network of the pelvic and lumbar regions.
• Lateral Sacral Arteries: The iliolumbar artery may also anastomose with the lateral sacral arteries, helping to supply the sacral vertebrae and nearby structures.

Variations

The iliolumbar artery may show some variations in its origin or branching pattern. In some cases, the artery may arise directly from the common iliac artery instead of the internal iliac artery. Additionally, the branching of the iliac and lumbar divisions may occur at varying levels, depending on individual anatomical differences.

Function

The iliolumbar artery serves multiple critical functions in supplying blood to the pelvic region, lower back muscles, and bones. Its role is divided among several structures, including muscles of the posterior abdominal wall, the spine, and the pelvic bones. Below is a detailed description of its functions.

Blood Supply to the Muscles of the Lower Back

The iliolumbar artery provides oxygenated blood to several important muscles in the lower back and pelvic regions. These muscles play essential roles in movement, stability, and posture.

• Psoas Major Muscle: One of the primary muscles supplied by the iliolumbar artery is the psoas major, which is crucial for hip flexion and lumbar spine stability. The psoas major connects the lumbar spine to the femur, aiding in leg movement and stabilization of the trunk.
• Quadratus Lumborum Muscle: Another muscle supplied by the iliolumbar artery is the quadratus lumborum, which plays a role in lateral flexion of the spine and supports spinal stabilization. It helps maintain posture and assists in breathing by stabilizing the lower ribs during respiration.
• Iliacus Muscle: The iliac branch of the iliolumbar artery supplies the iliacus muscle, which, along with the psoas major, forms the iliopsoas complex. This complex is involved in hip flexion and helps with lower limb movement.

By supplying these muscles, the iliolumbar artery ensures that the lower back and hip regions remain functional and well-perfused during movement and weight-bearing activities.

Blood Supply to the Lumbar Vertebrae and Spine

Another essential function of the iliolumbar artery is to provide blood to the lumbar vertebrae and surrounding spinal structures. The artery helps maintain the health and integrity of the bones and tissues that form the lower spine.

• Lumbar Vertebrae: The lumbar branch of the iliolumbar artery ascends toward the lumbar vertebrae and provides blood to these bones. This supply is vital for the nourishment of the vertebral bodies, which support much of the body’s weight and facilitate movement in the lower back.
• Intervertebral Discs and Ligaments: The blood supply from the iliolumbar artery may also contribute to the nourishment of the intervertebral discs and ligaments between the vertebrae. These structures are essential for spinal flexibility and shock absorption during movement.

The contribution of the iliolumbar artery to the spinal vascular network ensures that the bones and connective tissues in the lumbar region remain healthy and capable of supporting both movement and load-bearing.

Blood Supply to the Ilium and Pelvic Bones

The iliac branch of the iliolumbar artery is responsible for supplying blood to the iliac fossa and the ilium, the large bone that forms the upper part of the pelvis. This supply is crucial for the structural integrity of the pelvic bones and the surrounding muscles.

• Ilium: The iliac branch provides blood to the ilium, the broad, fan-shaped bone that is part of the hip structure. By nourishing the iliac bone, the artery ensures that this key component of the pelvis remains strong and functional.
• Periosteum of the Iliac Bone: The periosteum, a dense layer of vascular connective tissue covering the bones, also receives blood from the iliac branch. This supply supports bone health, particularly during growth or healing processes after injury or surgery.

By providing blood to the pelvic bones, the iliolumbar artery contributes to the structural support needed for standing, walking, and other movements involving the pelvis and lower limbs.

Contribution to the Pelvic and Lumbar Vascular Network

The iliolumbar artery forms important anastomoses (connections) with other arteries in the pelvic and lumbar regions, helping to establish a redundant and flexible blood supply for critical structures.

• Anastomosis with Lumbar Arteries: The lumbar branch of the iliolumbar artery connects with the lumbar arteries that originate from the abdominal aorta. These connections ensure that the muscles, bones, and tissues of the lower back have multiple sources of blood, creating a robust vascular network that can compensate in the event of arterial blockage or injury.
• Anastomosis with Deep Circumflex Iliac Artery: The iliac branch forms connections with the deep circumflex iliac artery, further supporting the blood supply to the iliac crest and iliacus muscle.
• Anastomosis with Lateral Sacral Arteries: The artery also anastomoses with the lateral sacral arteries, which supply blood to the sacral vertebrae and surrounding tissues, contributing to the vascular supply of the sacral and lower lumbar regions.

These anastomotic connections ensure that the iliolumbar artery plays a central role in maintaining adequate blood flow to the pelvic and lumbar regions, even in cases of injury or vascular disease affecting other arteries.

Support for Postural Stability and Movement

By supplying blood to key muscles, bones, and connective tissues, the iliolumbar artery indirectly supports postural stability and movement. The muscles it supplies, particularly the psoas major and iliacus, are involved in maintaining balance and allowing for efficient movement of the legs and torso. Additionally, by nourishing the lumbar vertebrae and pelvic bones, the artery helps maintain the structural integrity necessary for supporting body weight and facilitating motion.

Clinical Significance

The iliolumbar artery is clinically significant due to its role in supplying blood to the lower back muscles, lumbar vertebrae, and iliac bone. Its close proximity to important structures, such as the psoas major muscle and lumbar vertebrae, makes it a key consideration during surgical procedures involving the lower spine or pelvis. Injuries to the iliolumbar artery during surgeries, such as spinal surgery or pelvic fracture repairs, can lead to significant bleeding due to its vascular supply to the lower back and pelvic regions.

The artery’s contribution to the lumbar and pelvic vascular network, particularly through anastomoses with the lumbar and sacral arteries, is important for maintaining adequate blood flow to the region. In some cases, its branches may become involved in collateral circulation if there are blockages or vascular diseases in other pelvic or lumbar arteries. It is also a landmark in procedures such as spinal fusion or hip surgery, where the preservation of blood supply is crucial for healing and recovery.