Three-dimensional analysis of the sagittal profile in surgically treated Lenke 5 curves in adolescent idiopathic scoliosis.

STUDY DESIGN Retrospective. OBJECTIVES To determine how the pre- and postoperative three-dimensional (3D) sagittal profiles of Lenke 5 curves in idiopathic scoliosis patients compare to unaffected controls. Prior research evaluating the sagittal plane of Lenke 5 (thoracolumbar/lumbar) curves in 2D suggests that the major curve is hypolordotic. METHODS Patients with Lenke 5 curves treated with thoracolumbar/lumbar posterior fusion who had biplanar radiography (with 3D reconstruction) preoperatively (Pre) and 2+ years postoperatively (PO2Y) were included. A cohort of similarly aged controls (C) without spinal pathology was identified. The following 3D sagittal measurements were compared both pre- and postoperatively to controls: T1-T10, T10-L3, L3-S1, and pelvic incidence (PI). Kyphosis is designated by positive values, and lordosis by negative values. RESULTS Nineteen Lenke 5 patients and 125 controls were included. Preoperatively, Lenke 5 patients were hypokyphotic relative to controls from T1 to T10 (30° ± 13° vs. 42° ± 9°, p < 0.001) and hyperlordotic from T10 to L3 (- 26° ± 15° vs. - 13° ± 12°, p < 0.001). Lenke 5 spines were less lordotic from L3 to S1 (- 41° ± 9° vs. - 47° ± 7°, p = 0.004). PI was similar between groups (Lenke 5 Pre: 48° ± 13°, C: 46° ± 10°, p = 0.49). Postoperatively, the area of principal deformity (T10-L3) remained hyperlordotic (PO2Y: - 23° ± 10° vs. C: - 13° ± 12°, p < 0.001). The proximal and distal uninstrumented segments demonstrated spontaneous sagittal correction, becoming similar to controls: T1-T10 (PO2Y: 41° ± 12° vs. C: 42° ± 9°, p = 0.421) and L3-S1 (PO2Y: - 48° ± 9° vs. C: - 47° ± 7°, p = 0.56). CONCLUSION When measured in 3D, Lenke 5 curves were more lordotic than controls in the periapical region of the major coronal curve. Posterior correction improved sagittal alignment, including spontaneous sagittal correction of the unfused segments. However, ~ 10° of hyperlordosis persisted in the instrumented/fused T12-L3 segment. Intraoperative correction strategies should take this preoperative increase in 3D sagittal deformity into account during rod contouring as well as compression/distraction to restore more normal sagittal alignment. LEVEL OF EVIDENCE III.