What is the management plan for a patient with 5 non-rib bearing lumbar type vertebral bodies?

Management of 5 Non-Rib Bearing Lumbar Type Vertebral Bodies

This anatomical variant represents a lumbosacral transitional vertebra (LSTV) requiring accurate vertebral numbering and careful surgical planning to prevent wrong-level interventions, but does not require treatment unless symptomatic pathology develops at specific levels.

Understanding the Anatomical Variant

• Five non-rib bearing lumbar-type vertebrae indicates either a thoracolumbar transitional vertebra (TLTV) with 13 thoracic vertebrae and 5 lumbar vertebrae, or an S1 lumbarization creating 6 lumbar-type segments 1, 2.
• LSTVs occur in approximately 12.6-12.9% of patients undergoing spinal surgery and are frequently associated with TLTV (78.4% of cases) 1, 2.
• The most common configuration is T13 TLTV (67.8% of transitional cases), which when combined with normal lumbosacral anatomy, produces 5 non-rib bearing segments 2.

Critical Diagnostic Steps

Obtain whole-spine radiographs (cervical through sacrum) to establish accurate vertebral counting before any surgical or interventional planning 1, 2.

• Count vertebrae from C2 downward to the sacrum, identifying the lowest rib-bearing vertebra as the last thoracic segment 1, 2.
• On sagittal CT or MRI, examine whether the lumbosacral transitional anatomy resembles normal L5-S1 (suggesting Castellvi LSTV) or normal S1-S2 (suggesting S6 LSTV with lumbarization) 2.
• On axial imaging at the S1 upper segment level, determine if morphology appears S2-like (Castellvi LSTV) or L5-like (S6 LSTV) 2.
• Use three-dimensional CT when available, as it is most suitable for detecting transitional vertebrae 2.

Clinical Implications for Symptomatic Patients

If the patient develops low back pain, investigate three specific pain generators associated with LSTV 3:

1. The level immediately above the transitional segment (most common pain source)
2. The contralateral facet joint when unilateral transitional anatomy exists
3. The anomalous articulation itself when present

• Perform targeted physical examination with percussion over each potential pain generator to localize symptoms 3.
• Order MRI of the complete lumbosacral spine when symptomatic to identify disc degeneration, facet arthropathy, or stenosis at vulnerable levels 1, 3.

Surgical Planning Protocol

Vertebral level miscounting occurred in 54% of LSTV patients at initial outpatient evaluation, and surgical plans required alteration in 15% of cases after recognizing true spinal counts 1.

• Establish definitive vertebral numbering using whole-spine imaging before scheduling any procedure 1.
• Mark the surgical level using fluoroscopy with counting from a known landmark (typically C2 or the sacrum) rather than assuming standard anatomy 1, 2.
• Document the transitional anatomy explicitly in the operative plan, noting whether using radiographic numbering (counting actual vertebrae) versus clinical numbering (functional segments) 2.
• For Castellvi type-IIIb LSTV specifically, recognize that the vertebra below should anatomically be called S1, but clinically functions more like S2 2.

Management When Asymptomatic

• No treatment is required for asymptomatic LSTV, as it represents a normal anatomical variant 3.
• Document the variant in the medical record to prevent future surgical errors 1.
• Educate the patient that this anatomy may cause confusion in future medical care and they should inform providers 1.

Common Pitfalls to Avoid

• Never assume standard 5-lumbar, 12-thoracic anatomy without whole-spine imaging - this causes wrong-level surgery in 15% of LSTV cases 1.
• S1 lumbarization is miscounted more frequently than L5 sacralization (28 versus 10 cases in one series), so maintain higher suspicion when counting appears to show 6 lumbar segments 1.
• Overlooking coexisting TLTV compounds numbering errors, as 78.4% of LSTV patients have both anomalies 2.
• Standard lumbar-only MRI may miss the transitional anatomy if the field of view doesn't include lower thoracic spine 1.

When Intervention Becomes Necessary

If symptomatic pathology develops requiring surgery or intervention:

• Follow standard clinical guidelines for the specific pathology (disc herniation, stenosis, fracture, infection, malignancy) as outlined in disease-specific protocols 4.
• Apply the same treatment algorithms used for standard anatomy, but with meticulous attention to correct level identification 1.
• Consider that the level above the transitional segment experiences increased biomechanical stress and may develop earlier degenerative changes 3.