Progression of segmental thoracic kyphosis and metal failure following thoracolumbar hemivertebra resection in congenital scoliosis

Hemivertebra resection (HVR) via the posterior approach is considered the surgical treatment of choice for congenital scoliosis (CS) in paediatric patients. However, alterations in sagittal alignment, particularly in the thoracolumbar region, may have adverse effects following HVR. This study aims to investigate the changes in segmental thoracic kyphosis (TK) and occurrence of metal failure following thoracolumbar hemivertebra resection (HVR) in patients with CS. A total of 28 CS patients who underwent HVR between T11 and L2 were retrospectively reviewed. They were categorized into two groups based on the presence of metal failure: the MF+ group ( n = 12) and the MF- group ( n = 16). Data collection included demographics (age and obesity, defined as ≥ 95th percentile), operative outcomes, radiological variables, and complications. Radiological assessment comprised both coronal (Cobb’s angle, segmental Cobb’s angle, coronal balance) and sagittal (sagittal vertical axis, TK, segmental TK, and lumbar lordosis) parameters. Multivariate logistic regression analysis was used to identify factors influencing metal failure. Metal failure occurred in 42.9% of patients over a mean follow-up of 61.1 months. The mean segmental TK progression from postoperative to the last follow-up was significantly greater in the MF+ group (35.3°) than in the MF- group (20.2°) ( P = 0.007). The elastic Net model identified three candidate predictors associated with metal failure: segmental TK progression, age, and obesity. These candidate predictors were subsequently included in the Firth’s penalized logistic regression model: segmental TK progression (OR, 1.12; 95% CI, 1.21–1.32), age (OR, 1.33; 95% CI, 1.01–2.07), obesity (OR, 2.57; 95% CI, 0.35–21.28). Progression of segmental TK is a common radiographic finding following HVR for thoracolumbar lesions in patients with CS, which is significantly associated with metal failure. III.