Influences of lumbo-sacral transitional vertebrae for anterior lumbar interbody fusion.

Lumbo-sacral transitional vertebrae (LSTV) are frequent congenital variances of the spine and are associated with increased spinal degeneration. Nevertheless, there is a lack of data whether bony alterations associated with LSTV result in reduced segmental restoration of lordosis when performing ALIF. 58 patients with monosegmental stand-alone ALIF in the spinal segment between the 24th and 25th vertebra (L5/S1)/(L5/L6) where included. Of these, 17 patients had LSTV and were matched to a control population by age and sex. Pelvic incidence, pelvic tilt, sagittal vertical axis, lumbar lordosis, segmental lordosis, disc height and depth were compared. LSTV-patients had a significantly reduced segmental lordosis L4/5 (p = 0.028) and L5/S1/(L5/L6) (p = 0.041) preoperatively. ALIF resulted in a significant increase in segmental lordosis L5/S1 (p < 0.001). Postoperatively, the preoperatively reduced segmental lordosis was no longer significantly different in segments L4/5 (p = 0.349) and L5/S1/(L5/6) (p = 0.576). ALIF is associated with a significant increase in segmental lordosis in the treated segment even in patients with LSTV. Therefore, ALIF is a sufficient intervention for restoring the segmental lordosis in these patients as well.