In the Relationship Between Change in Kyphosis and Change in Lordosis: Which Drives Which?

Abstract

Study Design: Retrospective single-center study. Objective: Investigate the effect of posterior instrumentation on the relationship between lordosis and kyphosis. Methods: Surgically treated patients with a minimum of 6 months of follow-up were analyzed. Asymptomatic volunteers served to show the normal anatomical relationship between thoracic and lumbar curves. Patients were stratified based on postoperative instrumentation: “Thoracic Fusion” = complete fusion of thoracic spine; “Lumbar Fusion” = complete fusion of lumbar spine; and “Complete Fusion” = fusion from sacrum to at least T5. Bivariate correlations and regression analysis were used to evaluate the relationship between change in thoracic kyphosis (ΔTK) and change in spinopelvic mismatch (ΔPI-LL; pelvic incidence-lumbar lordosis) before and after fusion. Analyses were repeated in “Lumbar Fusion” patients with flexible preoperative thoracic spines. Results: For asymptomatic volunteers, the natural anatomical relationship between TK and LL was found to be TK = 41% of LL (r = 0.425, P