Characteristics and Mechanisms of Adjusting Spinopelvic Sagittal Balance in Patients with Thoracic and Thoracolumbar Kyphosis

Abstract

Introduction This study determined the mechanisms of adjusting trunk sagittal balance and the impact of surgery on spinopelvic sagittal morphology and alignment in patients with thoracic and thoracolumbar kyphosis. Materials and Methods Whole spine and standing lateral radiographs of 49 Chinese patients with thoracic and thoracolumbar kyphosis were obtained before surgery, immediately after surgery, and in the final follow-up. A total of 171 asymptomatic Chinese adults were recruited as controls. The age at which the patients developed kyphotic deformity was recorded. The pelvic and spinal parameters were measured and the correlations of all parameters were analyzed. Results The mean age at which the patients developed kyphosis was 7.1 years. Preoperative mean pelvic incidence was 35.1 degrees, and mean pelvic tilt was −0.1 degrees, significantly less than those of normal subjects. Preoperative mean lumbar lordosis was 68.0 degrees, significantly higher than that of normal subjects. After surgery, kyphosis and lumbar hyperlordosis were significantly corrected, however, the preoperative and postoperative pelvic sagittal morphology and alignment made no difference, even in the final follow-up. There were no correlations between spinal and pelvic parameters before surgery. In the final follow-up, the correlations were recovered. Conclusion The mechanisms of adjusting the trunk sagittal balance in patients with thoracic and thoracolumbar kyphosis not only including pelvis anteverting, but also lumbar hyperlordosis. The latter serves as the main mechanism once skeletal maturation has been established. Although kyphosis and lumbar hyperlordosis were corrected by surgery, pelvic sagittal morphology remained unchanged. Surgery can reestablish the spinal sagittal balance and recover the correlations between spinal and pelvic parameters.