A Whole Spine MRI Based Study of the Prevalence, Associated Disc Degeneration and Anatomical Correlations of Lumbosacral Transitional Vertebra.

Study design: Retrospective cohort study.

Objective: Lumbosacral transitional vertebra (LSTV) results in numerical alterations of the lumbar and sacral segments. Literature concerning true prevalence, associated disc degeneration, and variation in numerous anatomical landmarks concerning LSTV is lacking.

Methods: This is a retrospective cohort study. The prevalence of LSTV was determined in whole spine MRIs of 2011 poly-trauma patients. LSTV was identified as sacralization (LSTV-S) or lumbarization (LSTV-L) and further sub-classified into Castellvi's and O'Driscoll's type respectively. Disc degeneration was evaluated using Pfirmann grading. Variation in important anatomical landmarks was also analysed.

Results: Prevalence of LSTV was 11.6% with 82% having LSTV-S. Castellvi's type 2A and O'Driscoll type 4 were the commonest sub-types. LSTV patients demonstrated considerably advanced disc degeneration. The median termination level of conus medullaris (TLCM) in non- LSTV and LSTV-L groups was at middle L1 (48.1% and 40.2%) while in the LSTV-S group, it was at upper L1 (47.2%). The median level of right renal artery (RRA) in non- LSTV patients was at middle L1 in 40.0% of individuals while in the LSTV-L and LSTV-S groups, it was at upper L1 level in 35.2% and 56.2% respectively. The median level of abdominal aortic bifurcation (AA) in non-LSTV and LSTV-S patients was at middle L4 in 83.3% and 52.04% respectively. However, in the LSTV-L group, the most common level was middle L5 (53.6%).

Conclusion: The overall prevalence of LSTV was 11.6%, with sacralization accounting for more than 80%. LSTV is associated with disc degeneration and a variation in the levels of important anatomical landmarks.