Upright, prone, and supine spinal morphology and alignment in adolescent idiopathic scoliosis

Abstract

BackgroundPatients with adolescent idiopathic scoliosis (AIS) are usually investigated by serial imaging studies during the course of treatment, some imaging involves ionizing radiation, and the radiation doses are cumulative. Few studies have addressed the correlation of spinal deformity captured by these different imaging modalities, for which patient positioning are different. To the best of our knowledge, this is the first study to compare the coronal, axial, and sagittal morphology of the scoliotic spine in three different body positions (upright, prone, and supine) and between three different imaging modalities (X-ray, CT, and MRI).MethodsSixty-two AIS patients scheduled for scoliosis surgery, and having undergone standard pre-operative work-up, were included. This work-up included upright full-spine radiographs, supine bending radiographs, supine MRI, and prone CT as is the routine in one of our institutions. In all three positions, Cobb angles, thoracic kyphosis (TK), lumbar lordosis (LL), and vertebral rotation were determined. The relationship among three positions (upright X-ray, prone CT, and supine MRI) was investigated according to the Bland-Altman test, whereas the correlation was described by the intraclass correlation coefficient (ICC).ResultsThoracic and lumbar Cobb angles correlated significantly between conventional radiographs (68° ± 15° and 44° ± 17°), prone CT (54° ± 15° and 33° ± 15°), and supine MRI (57° ± 14° and 35° ± 16°; ICC ≥0.96; P < 0.001). The thoracic and lumbar apical vertebral rotation showed a good correlation among three positions (upright, 22° ± 12° and 11° ± 13°; prone, 20° ± 9° and 8° ± 11°; supine, 16° ± 11° and 6° ± 14°; ICC ≥0.82; P < 0.001). The TK and LL correlated well among three different positions (TK 26° ± 11°, 22° ± 12°, and 17° ± 10°; P ≤ 0.004; LL 49° ± 12°, 45° ± 11°, and 44° ± 12°; P < 0.006; ICC 0.87 and 0.85).ConclusionsAlthough there is a generalized underestimation of morphological parameters of the scoliotic deformity in the supine and prone positions as compared to the upright position, a significant correlation of these parameters is still evident among different body positions by different imaging modalities. Findings of this study suggest that severity of scoliotic deformity in AIS patients can be largely represented by different imaging modalities despite the difference in body positioning.

The biomechanical effect of single-level laminectomy and posterior instrumentation on spinal stability in degenerative lumbar scoliosis: a human cadaveric study

“…Despite inherent design weaknesses that are mostly related to the difficulty for in vitro studies to precisely replicate the biomechanical effects of decompression and instrumentation in patients with scoliotic spines, it has to be noted that all radiographic images of the specimens were taken in a supine position rather than a more natural weight-bearing standing position, which is known to increase Cobb angle measurements in patients with scoliosis and might explain why we did not find any lateral slippage. 10,51 Also, during mechanical testing, we did not apply compressive axial loading. However, applying axial compression while testing would create additional moments, especially in spines with various degrees of scoliosis, that could interfere with the loading directions and consequently have an effect on the loaddisplacement data.…”

Weight-bearing Imaging in Adolescent Idiopathic Scoliosis

“…In this study they found a generalized underestimation of morphological parameters of the scoliotic deformity in the supine and prone positions as compared with the standing position, although a significant correlation of thoracic and lumbar Cobb angles/apical vertebral rotation was still evident among different body positions by different imaging modalities. 21 All these studies agreed that Cobb angles are markedly underestimated by a margin difference of 2 to 21 degrees (mean: 8.8 degrees) between the supine and erect positions (►Table 1). Further, not only do these studies show an underestimation of the Cobb angle between standing and supine/ prone positions in scoliosis assessment, but also in vertebral rotation, thoracic kyphosis, and lumbar lordosis measurements.…”

Proper positioning of mice for Cobb angle radiographic measurements

“…(20,21) The diagnosis and management decision of scoliosis relies on the Cobb angle measurement and thus these measurements must be accurate and consistent. The measurement error for human subjects has already been exempli ed from various aspects (5,8,(22)(23)(24). However the effects of mouse positioning on angle measurement is unclear.…”