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Introduction
  • T11-L5
  • most common approach
  • provides access to the following
    • cauda equina
    • intervertebral discs
    • posterior elements
      • spinous processes
      • laminae
      • facet joints
      • pedicles
  • Common uses
    • disc decompression
    • nerve root exploration
    • spinal fusion
    • tumor debulking
Intermuscular plane
  • Between 2 paraspinal muscles
    • each has segmental supply from posterior rami of lumbar nerves
Approach
  • Position
    • prone (most common)
    • abdomen free with bolsters
      • reduces venous plexus filling
    • avoid pressure points at hip, chest
  • Incision
    • midline incision
    • tip of superior spinous process to spinous process of affected level
  • Position
    • lateral decubitus, affected side upwards & over break
    • hip flexed
    • opens interspinous spaces
  • Incision
    • from tip of superior spinous process to spinous process of caudal affected level
    • midline incision
  • Landmarks
    • tip of iliac crest: L4/5 interspace
    • posterior superior iliac spince: S2





  • Superficial dissection
    • skin
    • subcutaneous fat
    • fascial layer (lumbodorsal)
    • spinous processes
      • cartilagious tip in pediatric patients
    • paraspinal muscles stripped off lamina (subperiosteal) 
      • superficial (erector spinae)
        • course: transverse & spinous process of inferior vertebrae to spinous processes of superior vertebrae 
        • function: extend and stabilize back
      • deep: transversospinalis (multifidis & rotators)
    • facet joint
      • dissection laterally to tip of mamillary process
    • lateral dissection taken to transverse process
      • transverse process of lower vertebra is at level of facet joint
  • Deep dissection
    • ligamentum flavum
      • travels from superior aspect of inferior lamina to midway point of superior lamina
    • removed with kerrison from leading edge of lower lamina
    • epidural fat
    • dural covering (seen as blue-white covering)
      • dissection is kept lateral to protect dura & visualize roots
  • Extension
    • proximal
      • continue midline with incision as above
      • can be taken to C1
    • distal:
      • continue with midline incision as above
      • can be taken to sacrum
Dangers
  • vascular area between transverse processes
  • venous plexus surrounding nerves
  • nerve roots
  • exiting nerve root exits foramen below the same level pedicle and above the disc
  • posterior rami
 

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