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