Vertebral tethering's effect on lumbar spine development in adolescent patients with sacralization of L5: a comparative case-control study.

PURPOSE: Human spine development and ossification, from foetus to adolescent, is a complex, gradual process. Vertebra growth can be modulated by applying mechanical compression or distraction forces. Asymmetrical vertebra loading can thus create vertebral-body angular deformities and wedging. The aim of this study was to analyse vertebral body shapes on the latetal view of subjects with symptomatic lumbosacral transitional vertebrae (LSTV) and compare them to radiologically normal asymptomatic subjects.

METHODS

We compared skeletally mature adolescents with LSTV and sacralisation of L5 against asymptomatic controls. Spinopelvic parameters and vertebral wedging were compared for all lumbar vertebrae using their full-spine, sagittal plane, standing radiographs taken from 2015-2023. Multivariate logistic regression (adjusted for PI) was used to control for spinopelvic confounding, while intergroup differences in wedging and L1-S1 lordosis were assessed via two-tailed Student's t-tests.

RESULTS

The LSTV group (n = 19, mean age 15.4 ± 1.4 years) exhibited significantly higher PI and L1-S1 lordosis (p < 0.01) than the control group (n = 17, mean age 14.7 ± 1.7 years), with comparable sex distribution in both cohorts. Univariate regressions showed that vertebral wedging angles were significantly higher among LSTV patients than controls at all vertebral levels. Multivariate regressions adjusted for PI found no statistical difference in L1-S1 lordosis between the two groups (p=0.872). However, L5 remained significantly more wedged (p=0.017) among LSTV patients.

CONCLUSION

Findings suggested morphological adaptations at the transitional level, with higher L5 wedging angles among LSTV patients than among controls, independently of PI. LSTV acts as a posterior tether, modulating vertebral growth during development, potentially part of hyperextension mechanisms occurring above the transitional level to compensate for reduced mobility in the L5-S1 segment and hypoplastic discs. Longitudinal studies could help evaluate spinopelvic development over time among LSTV patients.