What are the different types of lumbosacral vertebra variations?
To understand exactly how your lower back is different, doctors use a classification system to describe the connection between your last lumbar vertebra (L5) and your sacrum. Think of it like a "map" that helps them pinpoint the source of your pain and decide on the best treatment.
The system was originally created by Dr. Castellvi and later updated by Dr. Arthur Jenkins to be more detailed. Here’s a simple breakdown:
Type 1: Almost touching
In this type, the wings of your last lumbar vertebra (usually L5), called transverse processes, are larger than normal and get very close to the sacrum, but they don't actually form a joint or fuse with it. Type 1A is when the transverse process of the L5 vertebra nearly touches the sacrum. Type 1B is when both sides nearly touch the sacrum.
Type 2: A false joint (i.e., pseudo-articulation)
Here, the enlarged transverse process (i.e., wing) of the last lumbar segment is so close to the sacrum that it forms a "false joint" (a pseudo-articulation). This isn't a true joint like your knee or elbow, but it creates a point of contact and movement that can cause inflammation and pain. Type 2A is when a false joint is formed when one side only. Type 2B is when the false joint is formed on both sides. Type 2C is when one side forms a false joint and the other nearly touches the sacrum.
Type 3: A solid fusion
In this type, the transverse processes of the last vertebra are completely fused to the sacrum on both sides, creating one solid bone structure. There is no movement at this connection point. This anatomy is not known to cause any pain. Therefore, this anatomy cannot be the source of backpain in patients with Type 3 LSTV.
Type 4: A mix of types
This is a combination type where the two sides of the L5 vertebra are different.
Type 4A - One side is completely fused (like Type 3), while the other is "nearly touching" (like Type 1).
Type 4B - One side is completely fused (like Type 3), while the other has a "false joint" (like Type 2).
Type 4C - One side is completely fused (like Type 3), while the other side is completely normal.
References:
Alonzo, F., Cobar, A., Cahueque, M., & Prieto, J. A. (2018). Bertolotti’s syndrome: An underdiagnosed cause for lower back pain. Journal of Surgical Case Reports, 2018(10), rjy276. https://doi.org/10.1093/jscr/rjy276
Castellvi, A. E., Goldstein, L. A., & Chan, D. P. K. (1984). Lumbosacral Transitional Vertebrae and Their Relationship With Lumbar Extradural Defects. Spine, 9(5), 493.
Jenkins, A. L., O’Donnell, J., Chung, R. J., Jenkins, S., Hawks, C., Lazarus, D., McCaffrey, T., Terai, H., & Harvie, C. (2023). Redefining the Classification for Bertolotti Syndrome: Anatomical Findings in Lumbosacral Transitional Vertebrae Guide Treatment Selection. World Neurosurgery, 175, e303–e313. https://doi.org/10.1016/j.wneu.2023.03.077
Kapetanakis, S., Chaniotakis, C., Paraskevopoulos, C., & Pavlidis, P. (2017). An Unusual Case Report of Bertolotti’s Syndrome: Extraforaminal Stenosis and L5 Unilateral Root Compression (Castellvi Type III an LSTV). Journal of Orthopaedic Case Reports, 7(3), 9–12. https://doi.org/10.13107/jocr.2250-0685.782
McGrath, K., Schmidt, E., Rabah, N., Abubakr, M., & Steinmetz, M. (2021). Clinical assessment and management of Bertolotti Syndrome: A review of the literature. The Spine Journal, 21(8), 1286–1296. https://doi.org/10.1016/j.spinee.2021.02.023
Zhu, W., Ding, X., Zheng, J., Zeng, F., Zhang, F., Wu, X., Sun, Y., Ma, J., & Yin, M. (2023). A systematic review and bibliometric study of Bertolotti’s syndrome: Clinical characteristics and global trends.