MRI May Serve as a Valid Alternative to Standing Radiography in Evaluating the Sagittal Alignment of the Upper Thoracic Spine
This study is of a retrospective radiographic design.Objective:
The objective of the study was to compare supine magnetic resonance images (MRI) with standing x-ray scanning in the evaluation of the sagittal alignment of the upper thoracic spine.Summary of Background Data:
X-ray films have been reported to be inaccurate in evaluating the proximal thoracic sagittal alignment because of poor visibility of the upper thoracic region. Previous studies have demonstrated the feasibility of supine MRI in evaluating spinal deformities in the coronal plane. However, no study has addressed the use of MRI for evaluating the sagittal alignment of the upper thoracic region.Methods:
Ninety-six adolescents with idiopathic thoracolumbar/lumbar scoliosis were enrolled. The visibility of the upper thoracic spine landmarks from C7 to T6 in the lateral standing x-ray films was first graded. For patients with moderate or good clarity of the landmarks of each vertebra from C7 to T6 on x-ray films, the vertebral sagittal angles from T1 to T5 and the angle of T2–T5 kyphosis were measured by 3 observers on standing x-ray films and supine MRI images, respectively. Intraclass correlation coefficients were used to determine the intraobserver, interobserver, and method reliability. The paired t test was performed to compare the measurements between the 2 methods.Results:
The visibility of the upper thoracic region in x-ray films was generally unsatisfactory, especially for T1 and T2, whereas all the vertebrae were clear in MRI images. Only 50 patients’ x-ray films were graded as moderate or good visibility in the upper thoracic spine. Measurements on MRI images gave excellent intraobserver and interobserver reliability (0.914–0.924 and 0.838–0.920, respectively), which were better than that on x-ray films (0.767–0.891 and 0.713–0.883, respectively). No significant difference was found between the 2 modalities in terms of sagittal angles of T3, T4, and T5 (P=0.680, 0.595, and 0.239, respectively) and T2–T5 kyphosis (P=0.105).Conclusions:
With excellent measurement reproducibility, a supine MRI image may serve as a valid alternative to a standing x-ray film for the measurement for T3, T4, and T5 sagittal angles and for the evaluation of upper thoracic kyphosis.