Discussion of Transitional vertebra
- Transitional vertebrae are frequently encountered developmental variants of the spine.
- They are found in approximately 20% of human skeletons
- Often involve the sacrococcygeal and lumbosacral junctions.
- The L5 vertebra can be incorporated into the sacrum ("sacralized") or the S1 vertebra can be incorporated into the lumbar spine ("lumbarized").
- The transitional vertebra retains partial features of the segments above and below it so that the total number of vertebrae in the spinal column remains relatively constant.
- Transitional vertebrae are usually incidental findings during radiologic evaluation but rarely, when an enlarged transverse process irritates adjacent tissues, can be symptomatic.
- The most clinically important aspect of transitional vertebrae is the potential for confusion over the labeling or assignment of vertebral levels during medical or surgical treatment planning.
 Imaging Findings for Transitional vertebra
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 References for Transitional vertebra
- Jack Diel, Orlando Ortiz, Richard A. Losada, Donald B. Price, Michael W. Hayt, and Douglas S. Katz. The Sacrum: Pathologic Spectrum, Multimodality Imaging, and Subspecialty Approach. RadioGraphics 2001 21: 83-104.