Rothenfluh DA, et al. - In the present study, experts intended to ascertain how the amount of thoracic kyphosis affected the sagittal profile and balance in the selective thoracic (STF) and thoracolumbar fusions. A total of 154 individuals were included. In STF, in SVA vs thoracic kyphosis, logistic regression against postoperative variation permitted calculation of a critical thoracic kyphosis of 23°, below which decline of the sagittal vertical axis is more hopeful. A rise in the SVA was shown by people with hypokyphosis, while it was sustained from preoperative to 2 years postoperative if thoracic kyphosis was above 23°. Thus, in hypokyphotic individuals, to possibly circumvent postoperative sagittal plane decline with mechanical and likely also clinical outcomes, a critical thoracic kyphosis should be strived for 23° and more.