What is Bertolotti’s Syndrome?
What is Bertolotti’s Syndrome?
Bertolotti’s Syndrome (BSy) is a spinal condition that arises from a congenital (present at birth) anatomical variation in the lower spine, known as a lumbosacral transitional vertebra (LSTV). This variation alters the normal structure and function of the junction between the lumbar spine and the sacrum—the base of the spine that connects to the pelvis.
In simple terms, this means that the last lumbar vertebra (usually L5) or the top part of the sacrum (S1) doesn't look or behave the way it typically should. These structural anomalies can place unusual stress on the spine and surrounding tissues, sometimes leading to chronic lower back pain, which is referred to as Bertolotti’s Syndrome when LSTV is the primary source of pain.
Not all LSTV causes BSy
It’s essential to understand that having an LSTV does not automatically mean someone has Bertolotti’s Syndrome.
LSTV is a relatively common anatomical variant, observed in 4–30% of the general population (Alonzo et al., 2018).
However, only about 4–8% of people with chronic lower back pain are found to have symptoms clearly linked to LSTV—qualifying as true Bertolotti’s Syndrome (Kapetanakis et al., 2017).
This means that many people with LSTV are completely symptom-free, and LSTV is often discovered incidentally during imaging for other issues.
Clinically, it is crucial for healthcare providers to determine whether the LSTV is actually the source of the patient's pain, or merely an incidental finding.
To better understand and categorize the anatomical variations seen in lumbosacral transitional vertebrae (LSTV), radiologist Alberto Castellvi developed a classification system that is widely used in both clinical practice and research. This system divides LSTVs into four main types (I–IV) based on how the transverse processes of L5 interact with the sacrum (sacral ala). Please see the next section for further details.
You can read more about spinal anatomy at this website: https://spinehealth.org/article/spine-anatomy/
We also have educational videos included in the “Podcasts and Videos” page
What is Castellvi classification of BSy?
Original classification by Dr. Antonio Castellvi
The modern classification of LSTV anatomy was introduced by Castellvi et al in 1984 to characterize the different types of transitional anatomy observed in patients (Castellvi et al., 1984). There are 4 broad categories of LSTV:
Modified classification by Dr. Arthur Jenkins
Dr. Jenkins and his team performed a retrospective cohort study of 150 patients to revise the Castellvi classification. Based on the teams findings, this revised classification better describes functional anatomy, identify uncaptured anatomy (namely, type I anatomy) and identify optimal surgical treatment (Jenkins et al., 2023). Based on Jenkins’ classification, there are 9 types of LSTV:
Type 1:
Type I: Overgrowth of one or both transverse processes of the measuring at least 19mm in width
Type II: One or both transverse processes are enlarged enough to form a pseudo-articulation (i.e., false joint) with the sacral ala.
Type III: There is complete fusion of both transverse processes to the sacral ala, i.e., a complete sacralization of the last lumbar segment.
Type IV: Mixed anatomy where one side forms a pseudo-articulation whereas the other side is fully fused to the sacral ala.
Type 1A: Enlarged transverse process on the last lumbar segment with less than 10mm gap, but over 2mm gap, between the transverse process and sacral ala on one side only. The other side has “normal” distance over 10mm.
Type 1IB: Both transverse processes of the last lumbar segment has less than 10mm gap, but over 2mm gap, between the transverse process and sacral ala.
Type 2:
Type 2A: Incomplete lumbarization/sacralization with enlarged transverse process that creates a pseudoarticulation with itself and the sacrum (less than 2mm distance) on one side only. The other side has “normal” distance of above 10mm.
Type 2B: Symmetrical anatomy where both transverse processes have a pseudo-articulation on both sides with the sacrum with less than 2mm distance.
Type 2C: Hybrid anatomy where one transverse process has Type II anatomy (i.e., forms pseudo-articulation with the sacrum) and the other transverse process has Type IA anatomy (i.e., has between 2mm to 10mm distance between itself and the sacrum).
Type 3:
Type 3: Bilateral lumbarization/sacralization with complete osseous (bone) fusion of the transverse processes to the sacrum.
Type 4:
Type 4A: Lumbarization/sacralization with complete osseous fusion of transverse process to the sacrum on one side only. The other side has Type I anatomy with transverse process at distance of less than 10mm from sacrum.
Type 4B: Lumbarization/sacralization with complete osseous fusion (i.e., Type 3 like anatomy) on one side and an incomplete lumbarization/sacralization of the transverse process on other side (i.e., type 2 like anatomy).
Type 4C: Lumbarization/sacralization with complete osseous fusion of transverse process to the sacrum on one side only. The other side has “normal” anatomy with transverse process at distance of more than 10mm from sacrum.
Diagnosis & Treatment
X-Ray image of Type 2B LSTV
CT image of Type 2B LSTV
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.