Lumbar degenerative kyphosis - Radiologic analysis and classifications

Study Design. Retrospective study of a consecutive patient series. Objectives. To review the radiographic classification of patients with sagittal imbalance due to lumbar degenerative kyphosis (LDK) and to determine correlation between thoracic and lumbar curve. Summary of Background Data. Lumbar degenerative kyphosis is one of the common spinal deformities in Asian countries, especially Korea and Japan. However, there have been few studies regarding the classification and treatment of this disease. Methods. Seventy-eight patients with LDK were analyzed and classified according to the standing lateral whole spine findings. Total lumbar lordosis (L1-S1), thoracic kyphosis (T5-T12), sacral slope, thoracolumbar angle (T11-L1), and sagittal vertical axis (SVA) were measured on the lateral view of the whole spine. Spinal curve deformities were classified into 2 groups according to the thoracolumbar (T-L) junction angle: flat or lordotic angle ( Group 1; N = 53) and kyphotic angle ( Group 2; N = 25). Results. In Group 1, significant correlations between the thoracic and lumbar curves (r = 0.772, P < 0.0001), and between the lumbar curve and sacral slope ( r = 0.785, P < 0.0001) were observed. By this result, Group 1 was classified as sagittal thoracic compensated group. In contrast, In Group 2, no correlation was found between the thoracic and lumbar curves in the decompensated group ( r = 0.179, P = 0.391), but we found a significant correlation between lordosis and sacral slope ( r = 0.442, P = 0.027). By this result, Group 2 was classified as sagittal thoracic decompensated group. There was significant difference in SVA between 2 groups ( P = 0.020). Conclusion. The angle of the thoracolumbar junction is an important parameter in determining whether a sagittal thoracic compensatory mechanism exists in LDK. We assumed that existence of a compensatory mechanism in the proximal spine is central to the determination of the fusion levels in the treatment of LDK.