Cervical sagittal alignment in Lenke 1 adolescent idiopathic scoliosis and assessment of its alteration with surgery: a retrospective, multi-centric study.

Abstract

To document baseline cervical sagittal characteristics in Lenke 1 adolescent idiopathic scoliosis (AIS) patients and assess the alteration in these parameters with surgery. Pre-operative and 2-year postoperative radiographs of 82 Lenke 1 AIS patients recruited from five hospitals were analysed. Selected radiographic parameters capturing regional and global sagittal alignment were measured. Comparison was made between groups based on baseline thoracic kyphosis (TK: TK < 20°, TK ≥ 20°). Pre-operative and postoperative values were compared-the change in each radiographic parameter was correlated with the degree of sagittal and coronal correction. At baseline, TK was 29.8° ± 16°, cervical lordosis (CL) was -1° ± 14°, lumbar lordosis (LL) was -57.1° ± 21°, C2-C7 sagittal vertical axis (SVA) was 16 ± 14mm and C7-S1 SVA was -15 ± 28mm; 44% of patients had cervical kyphosis. Patients with thoracic hypokyphosis had a significantly lower LL and more kyphotic cervical spine compared to those with thoracic normohyperkyphosis. The effect of surgery on TK depended on pre-operative thoracic sagittal alignment-TK increased in patients with thoracic hypokyphosis, but decreased in patients with thoracic normohyperkyphosis. Neither CL nor C2-C7 SVA changed significantly with surgery; 46% of patients still had cervical kyphosis postoperatively. There is a high incidence of cervical kyphosis at baseline in AIS patients-more so in those with pre-operative thoracic hypokyphosis. Unlike TK, CL is not significantly altered with surgery-improvement in CL correlates weakly with sagittal correction of the structural curve.