Impact of the Nuss procedure on spinal curvature across four time points: a longitudinal and subgroup analysis

Pectus excavatum (PE) and scoliosis are widely reported to be highly associated due to the anatomical relationship between the thorax and spine. While the Nuss procedure is commonly performed to correct PE, its impact on spinal alignment remains unclear. The aim of this study is to investigate the effect of Nuss procedure on spinal curvature dynamics across different stages of the Nuss procedure. This retrospective study analyzed 177 patients who underwent the Nuss procedure for PE correction between July 2011 and July 2024. Spinal curvature was evaluated by measuring Cobb angle (CA) at four stages: pre-operative, post-operative, pre-removal, and post-removal. Subgroup analyses were performed based on sex, age, thoracic morphology (symmetry), pre-operative Haller index (HI), and baseline CA to assess their influence on CA dynamics. Significant changes in CA were observed during the bar insertion and maintenance phases (pre-operative to post-operative: mean difference +1.09°, P=0.003; pre-operative to pre-removal: mean difference +1.12°, P=0.03). Subgroup analyses of CA dynamics across the four time points identified male sex (P=0.001), adolescence (10-19 years, P=0.047), asymmetric thoracic morphology (P=0.04), severe HI (HI ≥3.5, P=0.01), and baseline CA (both <10°, ≥10°, P<0.001) as key factors influencing these changes. Among patients with CA <10°, mean CA changes were 2.05°±3.59° after bar insertion and 2.10°±4.20° before removal. Conversely, in the CA ≥10° (scoliosis) group, mean changes were -3.60°±4.32° and -3.70°±4.37°, respectively. No significant CA changes were found between the pre-operative and post-removal stages. This study investigates the dynamic impact of the Nuss procedure on spinal curvature, with the most pronounced changes occurring during bar insertion and the maintenance phase. Yet, no significant changes were observed between the pre-operative and post-removal stages. Spinal alignment shifts throughout different stages of the procedure and is influenced by multiple factors, particularly sex, age, and pre-operative CA. Further research is needed to explore the underlying biomechanical mechanisms and to assess the long-term effects of PE correction on spinal alignment.