Obesity Is Associated With Increased Thoracic Kyphosis in Adolescent Idiopathic Scoliosis Patients and Nonscoliotic Adolescents.

Retrospective comparative cohort study.To compare radiographic parameters between adolescents with a greater body mass index (BMI) percentile to underweight individuals. Increased BMI percentile has been associated with increased complications after surgical correction of adolescent idiopathic scoliosis (AIS). However, association between BMI percentile and preoperative sagittal plane alignment has not been evaluated. The purpose of this study was to evaluate the effect of BMI percentile on sagittal alignment in AIS patients compared with nonscoliotic adolescents.Posterior-anterior and lateral spinal radiographs of 1,551 AIS patients with a thoracic major curve (Lenke 1-4) and 70 nonscoliotic adolescent patients were compared. BMI percentile was determined based on age and sex, and patients were divided into four categories: underweight (<5th percentile), normal-weight (5th-85th percentile), overweight (85th-95th percentile), and obese (≥95th percentile).Coronal plane deformity magnitude was not significantly different between the 4 categories of AIS patients (p = .51). Increased BMI percentile was associated with increased thoracic kyphosis globally (T2-T12: p < .005) as well as segmentally (T2-T5: p < .001; T5-T12: p < .001) in patients with AIS. This was also true in obese adolescents without spinal deformity (p < .04). Lumbar lordosis, pelvic incidence, and pelvic tilt were not significantly different between AIS patients in the four BMI percentile categories (p > .07). Pelvic incidence was significantly greater in AIS patients compared with nonscoliotic adolescents (54 ± 13 vs. 46 ± 11; p = .01).Increased BMI percentile is associated with increased thoracic kyphosis in AIS patients and nonscoliotic adolescents. Excess weight may reduce anterior vertebral growth. AIS patients have an increased pelvic incidence compared with nonscoliotic adolescents; however, this variable is not influenced by body mass. These relationships should be taken into account when planning sagittal plane deformity correction or considering neuro axis disorders (also associated with increased kyphosis) in patients with scoliosis.Level II.