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Lumbosacral transitional vertebrae (LSTV) are congenital segmentation anomalies at the lumbosacral junction, where the lowest lumbar vertebra shows features of sacralization, or the uppermost sacral segment shows lumbarization.

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They are common incidental findings with important biomechanical and procedural implications.

Epidemiology

• Prevalence: 4–30% in the general population
• Often asymptomatic
• When symptomatic, associated with Bertolotti syndrome (low back pain attributable to LSTV)

Embryologic Basis

• Result from abnormal cranio-caudal segmentation of the lumbosacral spine
• Leads to partial or complete assimilation or separation at L5–S1

Clinical Importance

• Prevents wrong-level spine surgery
• Guides targeted injections and surgical planning
• Explains atypical patterns of degeneration and radiculopathy

Bertolotti Syndrome

• Low back pain attributed to LSTV
• Pain generators:
  • Pseudo-articulation (Type II)
  • Contralateral facet overload (unilateral LSTV)
  • Adjacent level disc degeneration
• Diagnostic confirmation: image-guided anesthetic injection into pseudo-joint

Complications