Posterior Approach to Lumbar Spine

Indications

  • excision of herniated dsics
  • exploration of nerve roots
  • spinal fusion
  • removal of tumours

Position

  • prone
  • bolsters longitudinally under patient’s sides
    • abdomen free
      • reduces venous plexus filling around the spinal cord by permitting the venous plexous to drain directly into the vena cava
  • Mayfield head rest
  • GA

Landmarks

  • Spinous processes
  • Iliac crest = L4-5 interspace
  • Identify Level with II

Incision

  • Midline longitudinal incision
  • Start: depends on numbers of levels to be explored

Internervous Plane

  • Between 2 paraspinal muscles (erector spinae)
    • Receive segmental nerve supply from posterior primary rami of lumber nerves

Superficial Dissection

  • Inline with incision
    • Fat
    • Fascia
  • Reach spinous process
  • Detach paraspinal muscles subperiosteally using Cobb elevator
  • Dissect down the spinous process, lamina, facet joint
  • If needed
    • Strip facet joint capsule
    • Transverse process

Deep Dissection

  • Ligamentum flavum
    • Cutting attachment to the superior edge of the inferior lamina
    • Beneath it is
      • Epidural fat
      • Blue-white dura
    • Remove the rest of the ligamentum flavum & undersurface of lamina with a Kerrison Leskel
  • Stay lateral to dura
    • Identify nerve root

Dangers

  • Segmental vessels supplying paraspinal muscles
  • Posterior primary rami of lumbar nerves
  • Nerve roots
  • Venous plexus
    • Stop with gelfoam, cotton patties soaked in thrombin
    • Bipolar malis cautery
  • Iliac vessels
    • Injured if instruments pass through anterior portion of annulus fibrosus
  • Local measures
    • Remove additional portions of lamina
    • Remove portion of facet joint
    • Carry dissection far lateral onto transverse process
  • Extensile
    • From C1 to sacrum