Posterolateral Lumbar Fusion

Posterior view of the lower lumbar spine and sacrum with pedicle screws and rods from L4 to S1, and bone graft laid on the decorticated transverse processes
Posterolateral lumbar fusion, L4 to S1. Pedicle screws and rods with bone graft laid on the decorticated transverse processes. Original schematic drawn for orthofracs.com.

Indications

  • Degenerative spondylolisthesis with stenosis needing decompression
  • Isthmic spondylolisthesis with persistent symptoms after conservative care
  • Iatrogenic instability after wide decompression or facetectomy
  • Degenerative scoliosis, and reconstruction after tumour, infection or fracture

Position

  • Prone on a radiolucent Jackson or Wilson frame with the abdomen hanging free
  • Free abdomen lowers epidural venous pressure and blood loss
  • Hips extended to preserve lumbar lordosis
  • Pad eyes, ulnar nerves and anterior superior iliac spines, and confirm fluoroscopic access

Operative Steps

  1. Localise the level with fluoroscopy and make a midline incision
  2. Dissect subperiosteally along spinous processes and laminae to the facets, preserving the capsule of the cranial adjacent facet
  3. Continue laterally to the tips of the transverse processes, coagulating segmental vessels at the lateral border
  4. Entry point lies at the junction of the transverse process midline and the lateral border of the superior facet
  5. Open cortex with an awl, probe the pedicle and palpate for four intact walls with a ball-tip feeler
  6. Medial angulation increases caudally and is greatest at L5. Tap, then insert screws under fluoroscopy
  7. Decorticate transverse processes, pars and lateral facets with a burr until bleeding bone shows
  8. Pack graft over the decorticated bed bilaterally. Iliac crest autograft has the highest fusion rate but causes donor site pain
  9. Local laminectomy bone is a standard supplement. Extenders include allograft chips, demineralised bone matrix and ceramics
  10. BMP-2 is off label in the posterolateral gutter. Risks include ectopic bone, radiculitis, swelling and osteolysis
  11. Contour rods to lordosis, seat, lock and compress across the segment, then confirm with final imaging

Postoperative Care

Complications

  • Dural tear, repaired primarily with sealant and a period of flat bed rest
  • Pseudarthrosis, more likely with smoking, diabetes, osteoporosis and multilevel fusion
  • Adjacent segment disease above the construct, worsened by violation of the cranial facet
  • Screw malposition, with medial breach threatening the nerve root and anterior S1 breach threatening iliac vessels
  • Deep infection and epidural haematoma

Reviewed by Professor Phong Tran, Head of Orthopaedic Surgery, Western Health. Last updated 20 October 2026.