Lowest Instrumented Vertebrae Selection for Posterior Fusion of Lenke 5C Adolescent Idiopathic Scoliosis: Can We Stop the Fusion One Level Proximal to Lower-end Vertebra?

Background The most appropriate fusion levels remains challenging, especially in Lenke type 5 curves. In Lenke 5 adolescent idiopathic scoliosis (AIS) generally fusion includes the lower end vertebra (LEV). This study determines whether it is appropriate to fuse mild to moderate Lenke 5 curves to LEV-1, if possible. Materials and Methods Forty-two patients with mild to moderate Lenke 5 AIS that underwent posterior fusion were retrospectively evaluated. The preoperative goal was to stop the instrumentation at LEV-1 in all patients if possible. However, the final decision was made intraoperatively according to the alignment of the disc below lowest instrumented vertebra (LIV). In 19 patients, this goal was achieved and LIV was LEV-1, whereas 23 patients were fused to LEV. Hence, two groups occurred and they were compared in terms of coronal, sagittal, and LIV related parameters at 1 year and 3 years postoperatively. Surgical times were also noted. Clinical outcomes were assessed using scoliosis research society (SRS-22) and Short Form-36 questionnaires. Results Two groups were well matched according to preoperative values. Postoperative radiographic results were also similar, except LIV disc angle and LIV translation, which were significantly higher in LEV-1 group at 1 and 3 years followup (P < 0.05). Surgical times were significantly longer in LEV group (P = 0.036). No significant correction loss was observed between 1 and 3 years followup. There were no significant differences regarding postoperative clinical outcomes except the activity domain of SRS-22, which was significantly higher in LEV-1 group, but the significance was weak (P = 0.045). Conclusions Fusion to LEV-1was associated with the higher amount of LIV disc angle and LIV translation, which did not cause coronal and sagittal imbalance and decreased the quality of life scores. Hence, if intraoperatively a level disc below LIV can be achieved, fusion to LEV-1 may be an option in mild to moderate Lenke 5 curves, to save one more mobile segment.