Vasculature of the Back

Arterial Supply - Back's Bloodlines

• Segmental Arteries:
  • Posterior Intercostal Arteries (Thorax): Supply erector spinae, overlying skin.
  • Lumbar Arteries (Abdomen): Supply lumbar muscles, skin.
  • Lateral Sacral Arteries (Pelvis): Supply sacral canal structures, piriformis.
• Other Key Contributors:
  • Vertebral Artery: Cervical vertebrae, deep cervical muscles.
  • Subclavian Artery Branches:
    • Dorsal Scapular A.: Rhomboids, levator scapulae.
    • Suprascapular A.: Supraspinatus, infraspinatus.
    • Costocervical Trunk (Deep Cervical A.): Deep neck muscles.
• Distribution Pattern: Dorsal rami supply intrinsic back muscles & skin. Spinal branches supply vertebrae, cord.

⭐ The Artery of Adamkiewicz, usually a left posterior intercostal branch (T9-T12), is vital for lumbosacral spinal cord perfusion. Its damage causes anterior spinal syndrome.

Venous Drainage - Return Routes

• Vertebral Venous Plexuses (VVP): Primary network for the vertebral column & spinal cord.
  • Internal (Epidural) VVP: Located in the epidural space, within the vertebral canal, external to the dura mater.
  • External VVP: Surrounds the vertebral column (anteriorly & posteriorly).
  • Both plexuses anastomose freely with each other and with regional veins.
• Intervertebral Veins: Traverse intervertebral foramina.
  • Connect VVP with segmental veins of the trunk (e.g., posterior intercostal, lumbar veins).
  • Receive veins from the spinal cord and spinal nerve roots.
• Segmental Drainage Pathways:
  • To posterior intercostal veins → Azygos/hemiazygos system → SVC.
  • To lumbar veins → Ascending lumbar veins / IVC.
  • To lateral sacral veins → Internal iliac veins.
• Batson's Plexus (VVP component):
  • Valveless system; allows bidirectional blood flow (e.g., ↑ intra-abdominal pressure can reverse flow).

⭐ The valveless nature of Batson's (vertebral) venous plexus facilitates hematogenous spread of pelvic/abdominal malignancies (e.g., prostate, breast cancer) to the vertebrae, skull, and brain, bypassing pulmonary circulation.

Spinal Cord Supply - Cord's Critical Flow

• Longitudinal Arteries:
  • Anterior Spinal Artery (ASA):
    • From vertebral arteries.
    • Supplies anterior 2/3rds of cord.
  • Posterior Spinal Arteries (PSAs) (2):
    • From vertebral arteries or PICA (Posterior Inferior Cerebellar Artery).
    • Supply posterior 1/3rd of cord.
• Segmental/Reinforcing Arteries:
  • Radicular/Medullary Arteries: Enter via intervertebral foramina, anastomose with ASA/PSAs.
  • Artery of Adamkiewicz (Great Anterior Radicular Artery):
    • Largest segmental medullary artery; major supply to lumbosacral cord.
    • Typically arises T9-L2, usually on the left. Critical for lower cord perfusion.
• Venous Drainage:
  • Longitudinal (anterior/posterior spinal veins) & radicular veins.
  • Drain to Internal Vertebral Venous Plexus (Batson's - valveless, potential route for metastasis).
• Watershed Areas:
  • Mid-thoracic (e.g., T4-T8) & thoracolumbar junction; vulnerable to ischemia, particularly during systemic hypotension.

⭐ Occlusion of the Artery of Adamkiewicz can cause Anterior Cord Syndrome: characterized by bilateral motor paralysis and loss of pain/temperature sensation below the level of the lesion, with proprioception and vibration sense (posterior column functions) typically spared.

Clinical Pearls - Vascular Vulnerabilities

• Spinal Cord Ischemia:
  • Anterior Spinal Artery (ASA) syndrome: loss of motor, pain, temp; spares dorsal columns.
  • Watershed zones (mid-thoracic, T-L junction) vulnerable.
  • Risks: aortic surgery, hypotension, atherosclerosis.
• Artery of Adamkiewicz:
  • Key supply to lumbosacral cord.
  • Usually T9-L2 (left). 📌 Adam is Left at T10. Injury → ASA syndrome.
• Batson's Venous Plexus:
  • Valveless; aids metastasis (prostate, breast) & infection to spine.

⭐ Batson's plexus: direct hematogenous spread of pelvic/abdominal cancer to vertebrae, bypassing lungs.

• Spinal Epidural Hematoma:
  • Acute cord compression. Often venous origin from internal vertebral plexus.

High‑Yield Points - ⚡ Biggest Takeaways

• Arterial supply to the back: chiefly posterior intercostal and lumbar arteries.
• Spinal cord: supplied by one anterior & two posterior spinal arteries, plus segmental medullary arteries.
• Artery of Adamkiewicz: a key segmental medullary artery for lower spinal cord supply.
• Venous drainage: via internal (Batson's) and external vertebral venous plexuses.
• Batson's plexus: valveless, facilitating metastatic spread (e.g., prostate cancer to vertebrae).