Cervical Spine Compensation in Adolescent Idiopathic Scoliosis.

Study Design/setting: Cross-sectional.

Objectives: To determine associations between cervical spine alignment and Lenke type for adolescent idiopathic scoliosis (AIS).

Summary Of Background Data: Although the lumbosacral spine and pelvis are standard considerations for evaluation of AIS, few studies have examined cervical spine alignment. These studies did not consider Lenke types upon which treatment decisions are based.

Methods: Stratified random sampling from 3,654 full-length preoperative lateral films of patients in a multicenter database of surgically treated AIS was done to obtain a representative sample from all Lenke types and thoracic curve modifiers. The C2-C7 sagittal Cobb and C2-C7 sagittal vertical axis (SVA) distances were measured by reviewers unaware of the patient's Lenke classification. C2-C7 sagittal Cobb and C2-C7 SVA among curve types and thoracic modifiers was compared using analysis of variance.

Results: There were 387 females and 84 males among patients in 471 randomly selected films; mean age at surgery was 14.8 ± 2.0 years. Significantly less cervical kyphosis was seen in Lenke 3 or 4 curves and greater cervical kyphosis in Lenke 1, 2, 5, and 6 curves. No significant differences in C2-C7 SVA were seen.

Conclusions: Patients with AIS appear to compensate for abnormal thoracic sagittal alignment with changes in cervical sagittal alignment. This seems intuitive for Lenke 1 and 2 curves in which surgical restoration of thoracic kyphosis is a recognized goal and has been shown to improve cervical alignment. Cervical kyphosis was also noted in Lenke 5 and 6 curves, which suggests a need to consider compensatory thoracic and cervical sagittal alignment during surgical planning. Patients with Lenke 3 and 4 curves had more normal cervical alignment, which suggests that with the major portion of the curve located in the middle of the spine, there is more ability above and below to maintain a more normal sagittal alignment.