Changes in the Adjacent Segment After Thoracolumbar Posterior Instrumentation and Fusion Surgery in Thoracolumbar Junction Fractures

ABSTRACT

STUDY DESIGN: Retrospective study. OBJECTIVES: To evaluate changes in the adjacent segment after posterior instrumentation and fusion in thoracolumbar spinal fractures. SUMMARY OF LITERATURE REVIEW The incidence of adjacent-segment disease is increasing as spinal surgery becomes more common. Many studies have been conducted on the risk factors for adjacent-segment changes in the lumbar spine, but few articles have been published on this topic in the thoracolumbar spine. MATERIALS AND METHODS: The records of 50 patients who received treatment from 2000 to 2013 were reviewed retrospectively. They underwent posterior instrumentation and fusion due to thoracolumbar fracture and were followed up for more than 2 years. To evaluate changes in the adjacent segment, immediate postoperative and last follow-up values of the sagittal angle, disc height, and disc angle were compared between groups divided by age (more or less than 50 years), laminectomy, and fusion levels. The Pfirrmann grade of the discs proximal and distal to the fusion level was also measured using preoperative magnetic resonance imaging. RESULTS: Thirty-six patients were male and 14 were female. The average age of the 50 patients was 45.6 years, and the mean follow-up period was 4.3 years. There were no cases of adjacent-segment disease. The mean kyphotic sagittal angle progression was 6.8° (range, −11° to 28.5°, p=0.000). The mean change of disc height of the proximal adjacent segment was 0.3 mm (range, −1.6 to 3.4 mm, p=0.013) and 0.6 mm (range, −4.1 to 5.8 mm, p=0.013) in the distal adjacent segment. Laminectomy did not make a significant difference. In the group below 50 years of age, the angle of the adjacent segment discs increased by 0.8° (range, −3.1° to 5.1°, p=0.004) at the proximal adjacent segment and by 0.5°(range, −4.8° to 2.9°, p=0.016) at the distal adjacent segment. Proximal adjacent disc height decreased as the fusion levels increased. As the preoperative Pfirrmann grade increased, degenerative changes in the proximal adjacent segment disc tended to accelerate. CONCLUSIONS: Adjacent-segment disease after lumbar fusion surgery was not found in adjacent segments of the thoracolumbar spine. This seems to be due to the anatomical characteristics of the lumbar spine, which is more flexible than the thoracolumbar vertebra. The mobile segments of the lumbar spine may account for this difference, rather than the instrumentation and fusion procedure itself.