What is Bertolotti’s Syndrome?
Bertolotti’s Syndrome is a source of lower back pain that is caused by a slight difference in how the bones at the very bottom of your spine are shaped. This area, where your lower back (lumbar spine) meets your pelvis (sacrum), is called the lumbosacral junction. This variation in your spine is congenital, i.e., it was present from birth.
Think of your spine as a stack of building blocks. In most people, the last block of the lower back (called L5) is separate from the sacrum below it. In people with this condition, the L5 bone is either abnormally large and "bumps into" the sacrum, or it's partially or fully fused to it. This extra connection is called a lumbosacral transitional vertebra (LSTV).
Having a lumbosacral transitional vertebra (LSTV) is not always a problem
It's important to know that just having this bone variation (LSTV) does not mean you have Bertolotti's Syndrome.
LSTV is surprisingly common and is found in up to 3 out of every 10 people.
However, most of these people never experience any pain or symptoms from it. The LSTV is often discovered by accident when they get an X-ray or MRI for another reason.
Bertolotti’s Syndrome is diagnosed only when a doctor confirms that the LSTV is the direct cause of a person's lower back pain.
So, while many people have this anatomical variation, only a small number develop the painful symptoms that define Bertolotti's Syndrome.
How doctors classify the lumbosacral transitional vertebra (LSTV)
To help them understand and describe exactly how the wings of the L5 vertebra (i.e., the transverse process) is connected to the sacrum, doctors use a classification system. This system simply organizes the LSTV into different "types" based on what the connection looks like; for example, whether it's an enlarged transverse process (the wings of the vertebra) on one side or a complete fusion on both. This helps doctors communicate clearly about a patient's specific anatomy.
Most people have five lumbar vertebrae (L1-L5). However, some individuals are born with six. This happens when the first part of the sacrum doesn't fuse with the rest of the bone, creating an "extra" mobile segment. This variation, also known as lumbarization. In this instance, it is one or both of the transverse process of the L6 vertebra that forms a false joint (pseudo-articulation) or fuses with with the sacrum.
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.