The significance of lumbosacral curve vertebral body leveling in coronal correction of degenerative scoliosis

English Keywords:Degenerative scoliosis  Lumbosacral curve  Coronal tilt  Coronal balance distance

English Abstract:

  【Abstract】 Objectives: To analyze the correction of postoperative coronal imbalance in adult degenerative scoliosis patients undergoing spinal fusion surgery, and to explore the impact of leveling of the most tilted vertebra(L4 or L5) in the lumbosacral curve on the correction of coronal imbalance. Methods: A retrospective analysis was conducted on 61 patients(17 male and 44 female; aged 51 to 78 years, mean 63.57±8.41 years; body mass index 15.79-35.55kg/m2, mean 25.83±3.69kg/m2) who underwent degenerative scoliosis correction surgery between January 2019 and March 2023 in Tianjin Union Medical Center. The patients were categorized based on the Obeid classification and the length of fusion segments into concave long segment group(17 cases), concave short segment group(15 cases), convex long segment group(15 cases), and convex short segment group(14 cases). Coronal radiographic parameters[Cobb angle, coronal balance distance(CBD), coronal tilt angle] and sagittal radiographic parameters(sagittal vertical axis, thoracic kyphosis, lumbar lordosis, pelvic incidence, pelvic tilt, sacral slope) were measured on full spine anteroposterior and lateral X-rays preoperatively and on 3d postoperatively. The postoperative coronal and sagittal imbalance corrections were compared between groups. Pearson correlation analysis was performed to investigate the relationship between the correction ratio of the maximal coronal tilt angle in the lumbosacral curve(L4 or L5) and postoperative CBD. The operative time, blood loss, and visual analogue scale(VAS) pre- and postoperatively were compared between the four groups. Results: The postoperative coronal Cobb angle, CBD, and maximal coronal tilt angle at L4 or L5 of the concave long segment group, convex long segment group, and convex short segment group were statistically different from those before operation(P<0.05). In the concave short segment group, the postoperative coronal Cobb angle and maximal coronal tilt angle at L4 or L5 were significantly different from those before operation(P<0.05), while no significant difference was found between pre- and postoperative CBD(P=0.085). Pearson correlation analysis revealed a significant negative correlation(r=-0.570, P<0.01) between postoperative CBD and coronal tilt correction ratio in the convex group, with the linear regression equation being postoperative CBD=32.81-28.38 × coronal tilt correction ratio. When the correction ratio of the maximal coronal tilt angle at L4 or L5 exceeding 45% in convex coronal malalignment patients, it′s predicted that the CBD could be corrected to within 20mm. No significant correlation was found between postoperative CBD and the coronal tilt correction ratio in the concave group(r=0.098, P=0.59). Patients in both the convex and concave short segment groups had shorter operative time and less blood loss than long segment groups. Postoperative VAS scores improved significantly in all groups(P<0.05). Conclusions: In adult degenerative scoliosis patients with convex coronal malalignment, both short and long segment fusions are capable of correcting coronal imbalance. Concave coronal malalignment patients require long segment fusion for the correction of coronal imbalance. To achieve optimal coronal balance in convex coronal malalignment patients, a correction ratio of the maximal coronal tilt angle at L4 or L5 shall exceed 45%.