Two-Year Cervical Alignment Trajectories and Associated Radiographic Factors after Posterior Spinal Fusion for Lenke Type 1 Adolescent Idiopathic Scoliosis.

Abstract

Retrospective analysis of a prospectively collected cohort. To describe 2-year cervical alignment trajectories after posterior spinal fusion (PSF) for Lenke type 1 adolescent idiopathic scoliosis (AIS) and identify factors associated with absence of lordotic change. Postoperative cervical alignment after AIS correction is variable, and factors associated with trajectory remain unclear. We analyzed 189 patients with Lenke type 1 AIS who had radiographs obtained preoperatively, within 1 month postoperatively, and at 2-year follow-up. Preoperative cervical kyphotic alignment (C2-7 angle <0°) was present in 122 patients (64.6%). A subgroup of 74 patients had preoperative cervical kyphotic alignment and early postoperative T5-12 kyphosis gain (ΔT5-12 >0°). Lordotic change was defined as an increase in the C2-7 angle at 2 years; absence of lordotic change was defined as ΔC2-7 angle ≤0°. Multivariable logistic regression identified associated factors. Among the 122 patients with preoperative cervical kyphotic alignment, 97 (79.5%) remained kyphotic at 2 years. Among the 74 patients with preoperative cervical kyphotic alignment and early postoperative T5-12 kyphosis gain, 25 (33.8%) showed absence of lordotic change. Absence of lordotic change was associated with higher preoperative pelvic tilt (adjusted OR 2.12 per 5°, P=0.007), lower attained early postoperative T5-12 kyphosis (adjusted OR 0.49 per 5°, P=0.012), and preoperative |T1 tilt| ≥5° (adjusted OR 6.31, P=0.030). Greater magnitude of preoperative kyphotic C2-7 angle was associated with a lower likelihood of absence of lordotic change (adjusted OR 0.31 per 5°, P<0.001). Kyphotic cervical alignment remained common 2 years after PSF for Lenke type 1 AIS. Early postoperative T5-12 kyphosis gain alone did not fully distinguish later cervical alignment trajectories. Absence of lordotic change was associated with higher pelvic tilt, lower attained early postoperative T5-12 kyphosis, and greater T1 tilt magnitude. The clinical significance of these radiographic trajectories remains uncertain, as SRS-22 scores did not differ significantly across 2-year alignment categories. Level III.