Lumbosacral Transitional Vertebrae

Description

Ferguson radiograph in a 35-year-old man. AP radiograph angled cranially at 30° allows better characterization of the transverse processes of L5. LSTVs have been classically described as best imaged by using Ferguson radiographs.

Castellvi classification

Name

• Lumbosacral Transitional Vertebrae (LSTV)

General

• Relatively common variant seen in approximately 25% of the population
• Must be recognized by radiologist/ spine surgeon to avoid incorrect/ erroneous procedures/ operations
• Can be thought of as "lumbarized S1" or "sacralized L5" segment
• The degree of transition can vary from partial to complete fusion
• One of the accessory bones of the spine

Lumbarization of S1

• Considered assimilation of S1 to lumbar spine
• Less common than sacralization, seen in 2% of the population
• Characterized by the presence of six rib-free lumbar type vertebrae

Sacralization of L5

• Considered assimilation of the L5 level into the sacrum
• More common than lumbarization, found in approximately 17% of the population
• Characterized by the presence of 4 rib-free lumbar type vertebrae

Classification

• Castellvi classification of lumbosacral transitional vertebrae

Plain Radiographs

• Ferguson projection and lateral projection have been used
• Largely replaced by cross sectional imaging on CT and MRI

MRI

• The most accurate method is to count the vertebrae from C2 down to the sacrum, however uncommonly done
• Iliolumbar Ligament can be used as an anatomic landmark at L5

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Clinical Significance

• Bertolottis Syndrome

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See Also

• Accessory Bones Main
• Back Anatomy Main
• Radiology Main

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