Proximal junction kyphosis in adult scoliosis. best post-operative radiological predictors. Retrospective cohort study.

Background: Proximal junction kyphosis is the post-surgical radiographic event seen in the surgical plane after the fusion of spinal deformity. No common agreement on direct postoperative radiographic prognostic criteria for occurrences of proximal junctional kyphosis that justify close monitoring for the patients. The purpose of this study is to assess which immediate post-surgical radiographic variable is best in forecasting the occurrences of proximal junction kyphosis. Methods: Data for adult scoliosis patients who underwent curve correction were extracted from the hospital database. Pelvic and spinal parameters were measured, Fisher exact test was performed for continuous variables and the Chi-square test was used for noncontinuous variables to compare four immediate post-surgical radiographic variables for occurrences of proximal junctional kyphosis. These variables were; Restoration of hypothetical values of lumbar lordosis and thoracic kyphosis according to pelvic incidence, evaluation of global sagittal alignment. Restoration of the apex of lumbar lordosis to its hypothetical position according to the spine shape and evaluation of positive-sum and negative-sum of lumbar lordosis and thoracic kyphosis. Results: The excellent predictor for occurrences of proximal junctional kyphosis was restoration of the apex of lumbar lordosis to its hypothetical position according to the spine shape. The second good predictor for occurrences of proximal junctional kyphosis was evaluation of global sagittal alignment. The Restoration of hypothetical values of lumbar lordosis and thoracic kyphosis according to pelvic incidence and evaluation of positive-sum and negative-sum of lumbar lordosis and thoracic kyphosis were both poor predictors for occurrences of proximal junction kyphosis. Conclusion: Among the four proposed formulae for predicting occurrences of proximal junctional kyphosis, the position of the sagittal apex of lumbar lordosis is an excellent predictor for the development of proximal junctional kyphosis followed by global sagittal alignment. Therefore, during scoliosis deformity correction hypothetical position of the sagittal apex of lumbar lordosis should be used to decide the level of pedicle subtraction osteotomy or a suitable place to put lordotic cages to reduce the risk of the future occurrences of proximal junctional kyphosis.