Sagittal spinal and pelvic parameters in patients with Scheuermann’s disease: A preliminary study

Background: Sagittal spinopelvic parameters remain poorly defined in patients with Scheuermann disease (SD). For example, although pelvic incidence (PI) should approximate lumbar lordosis (LL) by 108, this is not true in patients with SD. This retrospective radiographic study was conducted to propose a new mathematical relationship between sagittal spinopelvic parameters in skeletally mature patients with SD. Methods: The following formula (D) was proposed [(thoracic kyphosis – 458) þ (thoracolumbar kyphosis – 08) þ (PI – LL) ¼ 6 108] and validated with standard spino pelvic parameters in patients with skeletally mature SD without prior spine surgery at 2 centers between 2006 and 2015. The T1 pelvic angle (TPA) was used as a measure of global balance with normal maximum of 158. Subgroup analysis was performed to compare D between balanced (TPA 158) and unbalanced (TPA . 158) patients with SD. Results: In patients with SD (n ¼ 30), half were female (n ¼ 15), the average age was 39 years, and the average D was 2.48. A significant correlation was discovered between D and both TPA (R² ¼ 0.75) and PI (R² ¼ 0.69). At TPA of 158, average D was 9.28. There was also a significant difference between balanced and unbalanced patients (8.78 6 11.68 versus 28.28 6 19.78, P ¼ .0003). Conclusions: This study of a new formula (D) to evaluate global sagittal balance in patients with SD found that accounting for the kyphosis maintained D within 6 108. Further study is planned to determine whether maintaining and/or restoring a normal D is associated with improved outcomes in patients with SD after surgery.