Lumbosacral transitional vertebra alters the mobility of the lumbar spine on flexion-extension radiographs.

PURPOSE: Lumbosacral transitional vertebra (LSTV) is a common anomaly linked to the degeneration of the lumbar spine. The aim of this work was to study lumbar spine mobility in subjects with and without LSTV using flexion-extension radiographs.

METHODS

In this retrospective single-center study, we identified subjects with flexion-extension radiographs and abdominopelvic CTs performed between years 2005-2023. LSTVs were graded according to Castellvi classification, and lumbar mobility evaluated through total lumbar lordosis, disc wedging angles, segmental lordosis angles, and range-of-motion (RoM) from the flexion-extension radiographs. Independent samples t-test and Mann-Whitney U-test were used for statistical analyses.

RESULTS

The study group comprised Castellvi types II-IV (n = 29, mean age 59.1 years, 62% males) and control group 20 subjects without LSTV (mean age 65.1 years, 35% males). The study group presented a smaller overall RoM of lumbar spine than controls (33.5°±14.2° vs. 38.3°±12.1°, p = 0.23). Distribution of total lumbar mobility differed in transitional L5/S1-level being 10.7% with study group and 22.2% with controls (p = 0.002); similarly, assessing disc wedging angles, extension and RoM were lower with study group than controls being 8.7 ± 4.8° vs. 12.9 ± 4.7° (p = 0.002) and 3.3 ± 3.8° vs. 7.3 ± 3.8° (p < 0.001), respectively. Same results were seen with segmental lordosis measurements: 15.7 ± 5.6° vs. 23.1 ± 4.5° (p < 0.001) and 3.3 ± 5.5° vs. 8.3 ± 3.8° (p < 0.001), respectively. There were no statistically significant differences of relative distribution of lumbar motion at the upper lumbar levels between the groups.

CONCLUSIONS

LSTV decreases mobility of the lumbar spine in the L5/S1-level but does not increase relative motion at the upper lumbar levels. The overall compensation of mobility seems to distribute equally throughout the superior lumbar segments and not excessively to the superior adjacent level.