Lumbarized sacrum as a relative contraindication for lateral transpsoas interbody fusion at L5-6

J Spinal Disord Tech. 2012 Jul;25(5):285-91. doi: 10.1097/BSD.0b013e31821e262f.


Study design: Retrospective review.

Objective: To determine if lumbarized sacra at the L5-6 level (functional L4-5) are a contraindication to a lateral transpsoas approach.

Summary of background data: Transitional vertebrae at the lumbosacral junction present mechanical and morphologic changes, though these changes have not been characterized with respect to the feasibility of a lateral transpsoas approach.

Methods: Three hundred fifty-one patients were scheduled for lumbar interbody fusion using a mini-open lateral transpsoas approach (XLIF) at L4-5 from 2004 to 2008 at a single institution. In patients with 6 lumbar vertebrae, accessibility, based on neuromonitoring, of the L5-6 level (functional L4-5) was reviewed. Qualitative assessments using axial magnetic resonance imaging (MRI) were performed and compared with a sample of patients with normal anatomy treated at L4-5.

Results: Of the 351 patients scheduled for treatment at L4-5, 10 (2.8%) were determined to have 6 lumbar vertebrae with the symptomatic level at L5-6. Of those 10, 2 (20%) could be treated using a lateral transpsoas approach, and 8 (80%) were converted to another approach after a corridor through the psoas muscle was not found, based on neuromonitoring feedback. Review of axial MRI showed a teardrop-shaped psoas detached from the lateral border of the disc space in patients with transitional anatomy unapproachable at L5-6, resemblant of L5-S1 in normal anatomy. In the 2 patients who could be safely approached, the psoas anatomy at L5-6 was similar to a normal L4-5 level, with a domed/helmet shape, attached laterally to the disc space.

Conclusions: Treating the L5-6 level using a lateral transpsoas approach in individuals with lumbarized sacra can be challenging due to anatomy more similar to the L5-S1 level in normal patients. Preoperative planning using axial MRI and intraoperative adherence to advanced neuromonitoring can aid in identifying and avoiding injury in these rare patients.

MeSH terms

  • Contraindications
  • Female
  • Humans
  • Lumbar Vertebrae / abnormalities
  • Lumbar Vertebrae / diagnostic imaging
  • Lumbar Vertebrae / surgery*
  • Male
  • Monitoring, Intraoperative / methods
  • Monitoring, Intraoperative / standards
  • Musculoskeletal Abnormalities / diagnosis*
  • Musculoskeletal Abnormalities / epidemiology
  • Postoperative Complications / etiology
  • Postoperative Complications / physiopathology
  • Postoperative Complications / prevention & control
  • Predictive Value of Tests
  • Preoperative Care / methods
  • Preoperative Care / standards
  • Prospective Studies
  • Psoas Muscles / abnormalities
  • Psoas Muscles / diagnostic imaging
  • Psoas Muscles / surgery*
  • Radiography
  • Retrospective Studies
  • Risk Factors
  • Sacrum / abnormalities*
  • Sacrum / diagnostic imaging
  • Sacrum / surgery*
  • Spinal Fusion* / methods