Direct vertebral rotation (DVR) spinal instrumentation for the correction of adolescent idiopathic scoliosis Lenke 5 C.

Objective: This study aimed to evaluate the efficacy of selecting the lowest instrumented vertebra (LIV) with extended upper instrumented vertebra (UIV) using the direct vertebral rotation (DVR) technique in patients with adolescent idiopathic scoliosis (AIS) Lenke type 5 C.

Methods: A total of 120 patients with AIS Lenke 5 C with a lower-end vertebra (LEV) at L4 were prospectively enrolled and randomized into two groups based on the planned LIV: L3 (n = 44) or L4 (n = 50). All patients underwent posterior instrumentation with the DVR technique, with the upper instrumented vertebra (UIV) positioned at the upper end vertebra (UEV) + 1 or + 2. The final LIV was determined intraoperatively based on fluoroscopic assessment of disc alignment after DVR correction. Clinical and radiographic outcomes, including coronal balance, sagittal alignment, and complications, were evaluated preoperatively, at six months post-surgery, and at a minimum three-year follow-up.

Results: The mean follow-up duration was 39.8 ± 3 months for both groups, with no significant difference between them (P = 0.782). Coronal balance correction rates were comparable between the L3 and L4 groups, showing no significant differences at the final follow-up (P > 0.05). However, the number of fused segments differed significantly, with an average of 7.8 levels in the L3 group and 8.7 levels in the L4 group (P = 0.001). The distance between the central sacral vertical line (CSVL) and the L3 inner pedicle on convex side-bending films was the primary parameter for selecting L3 as the lowest instrumented vertebra (LIV). Notably, no complications such as adding-on or distal junctional kyphosis were observed in both groups.

Conclusions: Selecting the LIV at L3, when feasible based on intraoperative disc alignment, can preserve spinal mobility and reduce the number of fused segments without compromising correction outcomes. The CSVL-L3 inner pedicle distance on preoperative convex side-bending films is a useful predictor for the selection of appropriate LIV level for AIS Lenke 5 C with DVR. These findings highlight the importance of individualized LIV selection and intraoperative assessment in optimizing outcomes for patients with AIS Lenke 5 C. Additionally, raising the upper instrumented vertebra (UIV) enhances the correction of the thoracic curve, levels the rib hump, and improves shoulder balance in patients with AIS Lenke 5 C.