Lumbosacral transitional vertebrae are associated with lumbar degeneration: retrospective evaluation of 3855 consecutive abdominal CT scans

OBJECTIVES: To assess the prevalence of lumbosacral transitional vertebra (LSTV) and associated spinal degenerative changes on abdominal CT scans in Caucasian population. MATERIAL AND METHODS: A total of 3855 abdominal CT scans of the year 2017 from a single hospital were retrospectively assessed for LSTV, disc degeneration (DD), and facet joint degeneration (FD). An age- and sex-matched 150-subject control group without LSTV was picked at random. Multivariable logistic regression was used for the analysis. RESULTS: LSTV was found in 1101 (29%) scans: Castellvi type I in 68%, type II in 16%, type III in 13%, and type IV in 3% of scans. Age- and sex-adjusted prevalence of DD was significantly higher in Castellvi type II and III groups at multiple lumbar levels, and in IV group at L4/5 than in control group (p < 0.001–0.034). At L5/S1, the prevalence of DD was significantly higher in the control group than in type II, III, or IV groups (p < 0.001–0.017). After combining Castellvi types II, III, and IV into one group, significant differences were found at all lumbar levels except L2/3 (p < 0.001–0.016). Prevalence of FD was significantly higher at L4/5 in Castellvi groups I, II, and III than in the control group (p < 0.001–0.002). When Castellvi types II, III, and IV were combined into one group, significant differences were found at lumbar levels L2/3, L3/4, and L4/5 (p < 0.001–0.021). CONCLUSION: Lumbosacral vertebrae of Castellvi types II, III, and IV are associated with greater lumbar degeneration, warranting meticulous evaluation of spinal anatomy, even on CT. KEY POINTS: • Lumbosacral transitional vertebra is a common incidental finding on abdominal CT scans with a high prevalence of 29%. • When assessing whole lumbar spine, lumbosacral vertebrae of Castellvi types II, III, and IV were associated with greater lumbar degeneration, warranting careful evaluation of the lumbar spine on abdominal CT scans.